and Dr. Ruth Genger, UW Madison Department of Plant Pathology
Admittedly, I have a bit of winter amnesia when it comes to potatoes. I turn to daydreaming in the fields of season’s past, wondering what worked and how did I come to that decision when assessing my potato plots? If you’re like me, when I first started participating in the organic potato variety trial project, the disease and insect rating criteria was a little intimidating. What do I look for and what do I compare this to? Is that black lined iridescent green bug a friend or a foe perched on the underside of Red Maria? I’m still learning and pictures have helped.
I’ve put together a photo journey for evaluating potato varieties below. As you walk the virtual fields, what do you notice? Are there pieces missing? Resources that have been helpful for you? Pictures that you have, or that we need that would be helpful in understanding what to look for, how to rate? How do the ratings form rate for you?
Step 1: Plan Ahead and Prepare
Tools of the trade: Just you, your clipboard with datasheets and a pencil are all you need for ratings. Some growers also take their camera/smart phone and take photos, get video footage to document.
Rating varieties should take 30 minutes to an hour, depending on how many varieties you are growing. Once I plant my potatoes, I map the variety trial plantings and I make a note in my calendar 6 weeks and 10 weeks into the season for when I need to rate potatoes.
Step 2: What do you mean by plant vigor?
Comparing and rating plant growth in relation to each other helps me understand plant vigor. For evaluating varieties 1 would equate to very feeble plants (in relation to other varieties planted) and 5 would mean the plant variety stands out for its fast, vigorous growth.
Step 3: Row Closure – taking the birds eye view of the canopy. Ratings relate to the percentage of plot for which the canopy is touching between rows.
Step 4: Weed Tolerance
Different potato varieties may exhibit different weed tolerance thresholds. It’s important to note, that growers should utilize their usual weed management strategies, whether it’s mulching/hand weeding, or cultivation/mechanical, combination of the two. The idea is to assess varieties that work for your farm/markets and see if there are specific nuances in organic systems. Ratings range from 1 where dense weeds are shading most of the potato plants to 5, the best case scenario (only a few small weeds under the potato canopy – an organic farmer’s dream).
Trickier questions! and a simpler approach to them
Now we come to some phenomena that are more difficult to assess – insect and disease damage. In some cases these might be obvious, but others can be very difficult to tell apart. For example, if leaves are brown and crisp, it could be due to hopperburn, caused by a small sucking insect, or to early blight, caused by a fungus – or perhaps another disease altogether.
In 2016, we are redesigning our evaluation sheets so that you can simply comment on the level of damage to leaves and stems, without having to make a diagnosis on the spot. We’ll be sure to provide enough space for comments – and if you can snap a picture or two, that is always helpful.
In steps 5-8, below, we walk you through some of the more common insect pests and diseases, since it’s always helpful to know more about what’s out in the field. Symptoms can vary so use these resources as guides, but be aware that diagnosis can be difficult.
Step 5: How not to get burned in assessing Hopperburn
The photo shows hopperburn severity. The leaves on the upper left would be rated a 5 (green, healthy and from left to right 4,3,2. All the leaves on the bottom would be rated a 1 – wherein leaves are curled with brown, dead edges. A call/email to Dr. Russ Groves Entomologist, or a look through the UW Vegetable Crop website,can also help demystify leafhopper burn.
Step 6: Colorado Potato Beetle Damage
Ratings should reflect evidence of damage based on overall appearance of the plot.
For example a rating of 1 equates to the most severe damage with only the potato stalks remaining and 5 being no damage from beetles or larvae.
Step 7: The infamous Other – assessing signs for other insect pests
Sometimes there will be mystery insects that feast on your potato plants. For example, this past year, I noticed lots of black striped green bugs as well as little holes in the leaves. When in doubt describe the damage the best you can in the comments section.
Step 8: No more dis-ease in assessing disease issues
There are many disease pressures with growing potatoes. Some are visible during the growing season, and others can be seen on the tubers at harvest. The main diseases you might see are illustrated below.
Late blight, that ferocious sporulating nightmare of a plant disease that caused the 1848 Irish potato famine and fueled massive emigration from Ireland, still sends shivers down the spines of any vegetable grower.
The disease is caused by the fungus-like microorganism Phytophthora infestans, – literally “plant infesting destroyer”. In addition to evaluating for evidence of late blight you can stay up to date on whether late blight is in your area through Blitecast, a resource developed by Dr. Gevens and the UW Vegetable Pathology team.” If you are in doubt and are concerned you may have late blight, send a leaf sample to Dr. Gevens.
Above all, don’t get too concerned about the exact rating descriptions. Take some time to size up your potato plants and notice the different varieties in relation to each other before you start to rate them. Are there major differences that stand out? The ratings are just a way to show which varieties were better or worse than others.
In all cases, don’t forget to celebrate your efforts and taste the results. Tasting feasts are a great way to get feedback from your friends, CSA members, market customers, and neighbors.
After wandering the virtual fields from tuber to table, let us know your thoughts?
What tips or resources do you need to help you better assess potato varieties during the growing season?
We’d love to hear from you as we make plans for field research and thanks for your feedback, participation.
Part 1 in a 3 part series of reflections from Grower Participants with the Organic Potato Variety Trials
by Erin Schneider, Hilltop Community Farm
& Ruth Genger, UW Madison Department of Plant Pathology Organic Potato Project
A potato is a potato is a potato, right? Famines result from such homogeneity in thinking – look no further than Ireland in the 1840’s & 1850’s. So where exactly do organic potatoes fit for our farms and markets in the Midwest? I had the opportunity to explore these and other questions during interviews with 26 of the 28 growers who participated in the Organic Potato Variety Trial research in 2015, spanning Midwest climates in Wisconsin, Minnesota, Iowa, Ohio, and North & South Dakota. The following are a summary of reflections I’ve gleaned from the interviews.
Why Participate in Variety Trials?
For the past six years, UW-Madison researchers have collaborated with organic growers to select potato varieties that excel under organic management. Varieties from multiple market classes experience a wide range of field conditions and management models at different farm scales. Participants are willing to take the time and space to participate in this project for a variety of reasons. Some are driven by the need to have a robust organic seed system, and being able to experiment with more than just the 6 – 8 varieties that show up in most seed catalogs is appealing. Having to rely on outside sources/inputs touches a nerve in the self-sufficient, resilient, Upper Midwesterner!
Several participating farmers are going beyond the diversity available in variety trials, and trialing potatoes grown from true seed as part of on-farm potato breeding trials. Even a few growers not formally researching true potato seed did their own crosses, driven by the need to tweak and experiment.
Which Comes First: the Potatoes or the Markets?
I asked farmers to comment on where potatoes fit with their farm systems and markets. For the farm system, farmers expressed an interest in learning more about soil management techniques that support building soil fertility and nutrition. Weed management strategies, whether mulching, mechanical hilling and (for some) tine weeding, hand pulling, or some combination, are perennial challenges for potato fields of all shapes and sizes. Seed piece handling is another topic of interest, both on how to best store seed pieces as well as techniques for greensprouting, in the interest of hastening emergence. Most people saved seed tubers from last year and grew these out in the 2015 season. In all cases they noted that potatoes saved from previous seasons had greater surface defects and disease pressure.
Another challenge is to identify organic potato varieties that work well for different markets. As farmers, researchers, and potato purveyors of all shapes and sizes, we have our work cut out for us in marketing potato terroir and diversity in a region known for its pragmatism and love of meat and carbs. A good fit for Russet Burbank, but what about Purple Peruvian or Barbara?
Needs and interests around variety selection were driven by customer feedback, but also by the grower’s desire to find potatoes that are nutrient dense, store well, and taste great. CSA and restaurants seem to be the most forgiving and receptive clientele for most farms introducing new varieties.
That said, potatoes seem to work well for season extension and storage shares. Potatoes also seem to have a good fit in terms of community engagement and education about vegetable research. Some growers are using variety trials as an education tool. It’s a crop most people are familiar with, it’s easy to handle, and can pack a lot of bulk into the menu. Growers are using potato trials for education in the context of community gardens, schools, cities, amongst growers and with farm employees/interns. We’ll have more details of this, and highlight a few of the farms, in future posts.
Another market trend that emerged from the interviews was interest in finding nutrient dense varieties. In this regard, purple varieties had a strong grower appeal, though lackluster yields across the board made for disappointing expectations. People were willing to make an exception for Papa Cacho as the shape is always a conversation piece for growers and eaters alike. With fingerlings there isn’t much room for middle ground. Farmers either are really into them or not.
As the variety trial ratings and data are analyzed there’s an interest in understanding whether certain varieties respond well to certain types of management strategies or production scale.
In most cases, a variety that did well for one farmer, didn’t work for another. As a participant myself, I am convinced that Red La Soda is the cosmopolitan potato as it seemed to perform in just any growing condition imaginable and may even be the potato that would survive a nuclear fall-out. As we sift through the ratings data, other standout varieties may emerge and we will be sure to share in future blog postings.
Growers’ Experience(s) with Participation in Variety Trials
In terms of evaluation process, I observed that people expressed the need for another set of eyes in the field to assess plant vigor, disease and insect pressure. This was especially the case for first-time participants. They appreciate the detailed instructions, ideas for plant spacing and mapping, general ease of setting up trials, and filling out data sheets. Photographs also helped, though there is nothing that quite compares to in-person support, for example, when it comes to rating leafhopper damage.
Growers shared ideas for how to support training such as having field visits for new grower participants and including a resource list of for identifying diseases such as early and late blight.
Participants are encouraged to send in samples to the UW Plant Pathology Diagnostic Clinic, if questions arise and a field visit isn’t feasible.
Future training possibilities also included: hosting a field day in Wisconsin for grower participants; share video of field days so those who can’t attend can still access the information; identify a few experienced neighbor growers who would be willing to ‘mentor/train the trainer’.
After listening and learning of the season’s highlights I have a new appreciation for participatory research, and the time and processes involved in collaborating across county and state lines. What works in one region might flop in another and the separation might only be by a few hundred miles.The same is true with weather patterns. Some areas experienced continued rain for months at a time, others had to contend with 5 – 7 inch downpours in June, followed by dry spells through August, still others had the best season yet in terms of growing conditions.
As we sift through findings, we hope to tease out some of the characteristics that impact potato performance. We’d also love to hear from you. Are there any follow-up points you’d like to expand on in terms of what worked, what didn’t for your farm and market systems? Do you have photos you’d like to share? Are there other topics you’d like to delve into? We welcome your feedback and comments and greatly appreciate your participation!
On the horizon:
We’ll follow-up with a photo journey through the field ratings forms and focus on management. Woven into these gleanings, we’ll share performance/variety ratings based on your field data shared.
This year’s open house offers a great opportunity to visit and learn about potato variety trials and other horticulture crop research and demonstrations from local experts. There’s something for the whole family to glean and enjoy from exhibits, tastings and samples of fruit and vegetable to touring the latest research plots highlighting 200 different cultivars of vegetables and many cultivars of cold-hardy table and wine grapes.
University and Extension experts will be on hand to share their knowledge and answer your horticultural questions from potatoes to pollinators.
This should be a great time to pause, unwind from the fields and soak in the mid-summer abundance and horticultural diversity of Southern Wisconsin. Dress for spending time outdoors rain or shine. Hope to see you there!
with Drs. Amanda Gevens and Ruth Genger, UW Plant Pathology Department
“What’s the weather like?” I asked Rob, my husband, farm partner, and dedicated weather enthusiast.
“Well, the cooler, damper conditions that prevailed in June and that we’ve seen periodically thus far in July, tells me that it’s cloudy with a chance of spores.”
I did a double take, then realized, “Oh, you must have tuned into Blitecast and caught the latest late blight update from Dr. Gevens, Extension Plant Pathologist in Potatoes and Vegetables with the UW Vegetable Pathology team.”
“Of course, what did you think, I was talking about,” Rob responded, “the latest Madden-Julian Oscillation?”
Late blight, that ferocious sporulating nightmare of a plant disease that caused the 1848 Irish potato famine and fueled massive emigration from Ireland, still sends shivers down the spines of any vegetable grower. Late blight has been found in Adams, Waushara, Wood and Marquette Counties in Wisconsin this year, so it’s time to be on the lookout.
The disease is caused by the fungus-like microorganism Phytophthora infestans, – literally “plant infesting destroyer” – a member of a large group of plant pathogens that can infect a wide range of trees, vegetables and fruits. P. infestans, as it’s known to plant pathologists, can infect potatoes and tomatoes, as well as some nightshade weeds and petunia.
Late blight can come from infected seed potatoes or tomato transplants, potato cull piles and compost piles, volunteer plants, and is also spread aerially. The disease can devastate fields of potatoes and tomatoes we worked so hard to bring to fruition. None of us want to be in the position to tell our CSA members, customers, and grocers – sorry – no potatoes and tomatoes this year.
Fortunately, like the National Weather Service’s Storm Prediction Center, there are tools that farmers can utilize to forecast when an ‘inoculum storm’ would most likely infect given knowledge of the pathogen’s disease cycle. I spoke with Dr. Amanda Gevens of the UW-Madison Plant Pathology Department to learn more about disease forecasting and management options for late blight.
For on-farm management, Dr. Gevens recommends starting with good sanitation. Don’t keep discarded potatoes in cull piles, or compost infected tomato plants. Instead of saving seed potatoes, source certified seed potatoes, and consider planting shorter season varieties to avoid the pathogen. Raising one’s own tomato transplants can greatly aid in limiting disease introduction from other regions. High tunnels or greenhouses can limit initial infection by aerial ‘spore shower’ and has been shown to reduce late blight infection or greatly slow its onset.
Resistant varieties are always a boon to disease management. A handful of tomato varieties have significant resistance (but not immunity) to current late blight strains. These include; Iron Lady, Defiant, Mt. Magic, Plum Regal, and Matt’s Wild Cherry. In potatoes, few disease resistant options are available, but varieties with some tolerance include Satina, Jacqueline Lee, Sebago, Serran, and Kennebec.
Knowing the risk of infection helps us stay ahead of the pathogen, which is where disease forecasting models like Blitecast come in. Dr Gevens shared that, “‘blightcasting’ involves looking at temperature and periods of high relative humidity and assigning disease severity or risk values to each day. Research has shown that after a certain accumulation of ‘risk’ or severity values, disease is likely to occur if the pathogen is present and you have susceptible crops. While we can’t yet forecast where spores would be, temperature and relative humidity are helpful in managing pathogen persistence.”
Scouting for disease symptoms is another critical component of management. As a progressive farmer once said, “the best thing I can see in my field is my shadow”. Know the leaf disease symptoms on tomato and potato, and, in Wisconsin, send in samples for free testing (see below for details).
While not fun for any grower, fungicides can be part of the management solution. For organic growers, copper sprays are the most tried and true in managing this disease. Not all copper fungicides are approved for use in organic management, so check with your certifier or the OMRI list (http://www.omri.org/). Copper acts as a contact fungicide, so must be applied regularly to cover new foliage – it will not control an existing infection. Be mindful that copper accumulates in the soil and will also kill beneficial fungi. To spray or not to spray, as with many management decisions, involves trade offs. There is one other fungicide that has shown good results in limiting late blight in organic systems – EF400. This product isn’t OMRI approved but has been acceptable to certifying agencies.
Even less fun is the prospect of having to destroy your crop. “If you can’t shut down sporulation,” Dr. Gevens states, “it is best stewardship to shut down the crop. Once the plants are dead, the pathogen is dead and you can limit the production of more inoculum/spores for the remainder of your own farm and for your neighboring farms. Late blight is a community disease and it takes all growers of susceptible plants to participate in its management.”
Once confirmed in an area, the grower grapevine kicks in. Communication and planning beyond the farm gate help contribute to farmers’ ability to stave off damage. Wisconsin growers can report late blight to Dr. Gevens’ team and be assured of anonymity. Dr. Gevens relays, “When late blight has been confirmed in your ‘area’ of production the risk for infection increases on all farms. A sporulating lesion or lesions indicates that the pathogen was present and active for likely about one week. And, in that time, spores can be formed and could have moved aerially or through splash dispersal to new areas within a field and to new fields in an estimated 40 mile radius. Other fields may have already been infected but not yet observed for diseases. I’m conservative in my management recommendations for late blight in WI because the disease can be so destructive to potato and tomato crops impacting the economy and reputation of the growers of vegetables in our state.”
“Few diseases have the aggressiveness and longevity of late blight,” Dr. Gevens states. “I am fascinated by its ‘strength’, its impact on agriculture and history, and by the pathogen’s plasticity. It continues to outwit some brilliant growers and researchers since 1850.”
Dr. Gevens welcomes farmers of all scales, sizes, and production types, to be included in the UWEX Vegetable Crop Updates newsletter, which includes the disease forecasting information and reports for WI and the continental U.S. Growers are encouraged to send in pictures and samples to your local Extension agents if you need help. Knowing where the disease is and when it needs to be more actively managed can save on sprays and grower anxiety.
By Erin Schneider, Hilltop Community Farm, La Valle, WI
WithRuth Genger, UW-Madison
I am in the fields, prepping the soil in anticipation of peppers (potatoes already firmly tucked in), body and broadfork rocking like a metronome tick as if I am slowly learning how to salsa. Step, rock, slide, one, two, three, unearthing the earth worms and turning over the rye and vetch as I move across the soil floor. Whether you mechanically till or manually turn, roll and crimp or no-till, each year, as farmers we scramble to keep the beat and work with the seasonal rhythms to grow food without beating up our soils and bodies along the way. Potato production, as with many annuals and especially root/tuber crops, is hard on the soil. A Canadian study of rotation length in organic potato production systems found that four years of grain/forage rotation were required after a single year of potato production to restore microbial biomass to previous levels. Declining soil organic matter is a serious problem in long-term potato production systems.
Fortunately, there are options and good dance partners to help prop us up and give our bodies and our soils stamina. The longer I farm, the more I discover that mulching is a favored dance partner to support me (and my soil) when growing organic potatoes.
Dancing with mulch
Organic mulch materials include straw, hay, cover crops, woodchips, leaves, marsh grass, other crop residues, and even coffee chaffe – basically what’s most on hand and readily available. Cover crops can also be grown to maturity (flowering), mechanically killed, and left on the soil surface to provide an in-situ organic mulch for no-till planting. Ronald Morse, Professor Emeritus at Virginia Tech, has done extensive research on no till organic potato production. This topic deserves its own blog post, though Dr. Morse summarizes it better than I ever could in his paper, No-Till Production of Irish Potato on Raised Beds.
Beyond weed suppression
Mulches are useful for their role in weed management, moderating soil temperature and conserving soil moisture. But what are the long term effects of mulch in building organic matter, carbon cycling, and supporting the soil microbial community? In potato production system, with extreme disruption of the soil at planting and harvest, can mulch contribute to building or at least retaining soil organic matter? Or does the carbon just return to the atmosphere?
Hay and straw are among the most widely used organic mulches, with the latter being the focus of a research trial that Dr. Ruth Genger and team are working on this year in collaboration with five farms in Wisconsin, Minnesota and Ohio. in previous research station trials, the team has seen good weed control with mulch, and observed increased tuber yields from mulched plots in two out of three years. This year, the focus of the research has broadened to include straw mulch effects on soil carbon and nitrogen, plant nutrition, and greenhouse gas emissions from current and previous straw mulched plots.
I find this fascinating, and not just because I tend to geek out on soil biology, but also, how do you measure emissions from mulch? Collecting the samples is fairly easy, with the help of a video description from Professor Randy Jackson’s lab at UW Department of Agronomy.
Mulch timing, balancing inputs, and the long view
“In every good dance there is a step back too,” poet Robert Sund reminds me. I just discovered that the same is true with mulching. I look at my potato beds, which I covered with straw mulch just after planting a few weeks prior, and realize that the thickness just won’t cut it, with weed seedlings already poking through next to the Austrian Crescents that just emerged. While I only have a few hundred row feet, I can manage the expense, rake back the mulch and start again. But if you’re talking an acre of potatoes (or two or three, or more), multiple attempts at mulching aren’t a great option, and getting the timing and amount right become more important, especially given the vagaries of spring weather and the difficulty of bringing equipment into a wet field. Trials at the West Madison Agricultural Research Station this year will compare the effects of straw mulch applied at potato planting or at plant emergence, versus unmulched plots which are tine weeded and hilled. Labor needs and costs for these activities, as well as for ongoing weed management, will be recorded, and balanced against potato yield and quality.
At present, mulching these potato plots is a task for a large field crew to do by hand. At a small scale, this is manageable, but larger scale application will require mechanization options that could allow mulching to happen in conjunction with other field passes. A creative approach to straw mulch application was taken by on-farm research participants from New Story Farm, who unrolled a round bale over seed potatoes placed on a worked field plot, in comparison to planting in soil and mulching over this with straw. Thanks Stephanie and Dan for the great photos!
Long-term, Genger and team hope this year’s discoveries inform future research that takes a look at the soil microbial make-up and the long-term economics of what it takes, as farmers to grow our own mulch. The prospects of shifting the annual dance from expensive (i.e. cost of mulching inputs, labor/weed management) to wealth generating (less passes with the tiller, increased organic matter, the ability to grow your own etc.): that’s a farmer, researcher, and microbial community I could dance with.
One last turn rock n slide with the broadfork, I stop, look up, gaze honing in on the round bale and the mulching work that lies ahead. But first, just a little nap atop the bale, letting its pliable structure absorb the weight of my body, imagining what a potato (and the soil) might ‘feel’ knowing that it has this much support as it dances from tuber to table. Onward with mulch!
We’d love to hear from you
What are some of your mulching techniques and tips that you would recommend to other farmers?
Do you have experience with growing your own mulch for use in potato production? What worked? What were the challenges?
What practices do you use to build your soil organic matter?
As a CSA farmer, I love this time of year, that hit of ephemeral mojo, the smell of the soil exhaling with the first turn of the broadfork, passing of the tiller, and the resulting winter amnesia that will carry me through the next few months of intense planting. Spring is also all about timing and discovery.
Like the first asparagus that pokes through the ground, the anticipation of planting this year’s variety trials brings me joy. Our potatoes have arrived. I sift through the contents noting instructions and possible layouts, celebrating the colors textures of each individual tuber from Austrian Crescent to Gui Valley, and appreciation of how well organized, labeled and clear the instructions are. Thank you Ruth and team! How will these new varieties size up? Are they compatible with our soil and management practices? How do they respond to potential disease pressure and surface defects? Will our customers enjoy the tastes and textures of Papa Cacho or Early Blue?
And…wait, what exactly have I gotten myself into with this research and where will I put the potatoes?
This year 29 farmers are participating from 6 Upper Midwest states: Wisconsin, Minnesota, Iowa, North Dakota, and South Daktoa. While interests may vary for participating, you don’t need to have years of field research experience to engage in the project.
“Last year was the first year I participated in the variety trials. Honestly, I was just curious and this was a chance for me to satisfy my horticultural curiosity and I had a lot of fun along the way,” Laura Mortimore, Organic Farmer, Owner of Orange Cat Community Farm in Reedsburg, WI, shared. I also have interns at the farm and it was great to see them engage with the project as well. I appreciated having a crop that we could closely observe and monitor from planting to tasting.”
Whether you’re a veteran variety trialer like Laura, or new to the project, by now you’ve had a chance to connect with Ruth Genger, Project Lead at UW Madison Department of Plant Pathology, and discuss varieties you’d like to trial, what the research entails and how to communicate results. You have also received your soil sample bag in the mail and took your sample, sent it back for analysis (or will soon:-).
You will be receiving detailed instructions and suggestions for laying out your variety trial plot from Ruth and team when your potatoes arrive. The following is a general summary and flow of what to expect:
1. Tell us about your farm.This is important, so please remember to fill out farm the information sheet that you will receive. It should only take you 5 minutes. You can also fill out on-line.
What is emerging from past years’ data is that variety performance appears to correlate more closely with the soil type and management practices representative of each farm, rather than the variety itself. I was intrigued by this discovery – how you grow it is what you get. Maybe there is indeed a ‘potato terroir’. (Look for a future blog posting that summarizes discoveries from past research, and what this might mean for future opportunities).
2. Treat all varieties you have received (with respect) and in the same way. As with humanity, this is also the ‘golden rule’ of potatoes.
Plant the varieties on the same at the same spacing
Use the same management practices you’ve been using with potatoes and implement practices on the same date for all varieties.
Harvest all varieties within a few days of each other.
3. Spacing and Plot Layout. If you haven’t laid out a research trial before, you may be wondering how to ensure that tuber spacing is consistent between varieties. Fortunately, you have options and some excellent reference notes from Ruth and the Organic Potato Project Research team. The following diagrams are a few suggestions that you may find useful.
Most participants will receive 10 tubers for each variety. Ideally plant 2 rows of 5 tubers (side by side).
Formula to calculate length of row in ft: 5 tubers (within-row spacing x 5)/12
For ten tubers: (within row spacing x 10)/12
Plant your trial in a part of your field or garden that is reasonably uniform (soil type, slope, fertility, past use etc.).
Your potatoes will bechitted and ready for planting when they arrive. As Laura observed, “I also learned a lot from the variety trial last year and was surprised to find that all but one of the trial varieties performed really well at my farm. I think it was because the seed potatoes were well chitted. I found it interesting to plant seed potatoes prepared by someone else and compare this to my own seed potatoes. “
Mark each variety with a labeled stake
Map your area
5.Field Observations: From here it is farming as usual and Ruth notes the importance of following your usual rotation and management practices. Ruth will send an easy-to use-variety trial rating form for early and late season field observations, as well as a sheet for recording yield data at time of harvest.
6. Harvest at peak yield rather than for new potatoes. If you’re like me and your 4th of July just isn’t complete without a dish of early red potato salad, you’ll have to resist harvesting from your variety trial plots and stick to your standard plantings. At harvest time we’re looking for total weight and marketable/eatable weight, and any noticeable surface defects such as scab and scurf.
A sampling of the harvest at the Krouse Farm in 2014. Photo by Laura Krouse
7. Taste Testing (optional yet a fun and insightful way to involve your CSA members and market customers into giving feedback and a great excuse for a potluck or potato recipe contest). We were never huge fans of purple potatoes, but have found that our CSA members (especially the kids) love purple viking and it’s become a staple variety for us.
8. Share your results
Ruth and team have made it easy to record data and share via email. As your variety trials are underway, Ruth will send you this info.
9. Relax and settle into dormancy mode alongside your potatoes
10. Dream of spring, start again!
Hopefully you’ll find these suggestions helpful and let your horticultural curiosity be your guide. You never know what will emerge from the potato fields as Laura noted, ” I was surprised at how well all the varieties performed. Variety trial plants had no scab present, yet my seed potatoes had moderate scab. I’m looking forward to participating again this year, because it’s been great for our farm, has peaked my interest in growing different fingerling varieties, and I am more attuned to preparing and chitting seed potatoes.”
As always, if you have any questions about the trial, please feel free to contact Ruth by email (firstname.lastname@example.org) or phone (608-239-6088).
When we talk about seed potatoes, we mean tubers harvested from last year’s potato crop, which will be planted to grow this year’s crop. But what about potato seeds? Where do they fit in the potato life cycle? Potato seeds result from pollination of ovules, the “eggs” of plants, and are harvested from potato fruits. We often refer to them as “True Potato Seed” (TPS) to differentiate them from “seed potatoes” which are genetically identical clones of the parent plant.
TPS are anything but genetically identical! Potatoes are ‘highly heterozygous autotetraploids’ – they contain four copies of each chromosome, and there is considerable genetic variation between chromosomes. This makes for a wide range of plant and tuber types resulting from sexual reproduction. So if you start with TPS from an Adirondack Blue plant and expect to see uniform blocky tubers and blue flesh at harvest time, you may be surprised by the end result!
While you might not want all this variability in your production crop, it represents a rich opportunity to select for new varieties. Potato plants grown from true seed are a giant mix-and-match of characteristics from their parents – plant vigor, disease and insect resistance, maturity, tuber shape, color, taste, storability… it’s all there for you to select.
This coming season, Ruth, Amy, Doug and the rest of the Organic Potato Project team will be providing training on crossing potato varieties to interested farmers, and will provide you with true potato seed from crosses that performed well in previous organic trials. I for one am looking forward to participating. While it might take a bit of extra time and commitment of field space on my part, curiosity and long term benefits outweigh the upfront costs. I also think I’m getting a great deal and education in collaborating with researchers and fellow farmers. If you’re like me it took me a while before the simplicity of starting potatoes from seed sank in—indeed I had to think like a tomato before I could transition to thinking like a potato.
Let’s take a closer look at germinating and plant propagation techniques for true potato seed (TPS). (Hint: this is an awful lot like the process for starting your tomato plants in the greenhouse).
Seeding Possibilities: Propagation from True Potato Seed
True potato seed process in the Jansky lab at UW-Madison – from fruit to field. Pictures courtesy of Andy Hamernik and Shelley Jansky.
Shelley Jansky’s laboratory in the UW-Madison department of Horticulture focuses on developing potato germplasm for breeding and genetic research. The pictures above show their process of collecting seed, starting and transplanting seedlings in the greenhouse, and transplanting into the field for selection.
Start by seeding TPS shallowly into moist potting soil mix. Germination is often improved if seed is planted thickly – apparently potato seeds like company! On average potatoes planted from true seed take 3 weeks until true leaves form and they are ready for transplanting.
Transplanting Timeline – Insights from ‘Cindy Sheehan’
Ruth and team have been experimenting with lab and greenhouse propagation. These pictures follow the growth of plants from TW54, an F3 population after seedlings were transplanted to pots. These plants were grown to produce tubers in the greenhouse, so have been allowed to develop past the point where they would normally be transplanted to the field.
Priming seedlings, prepping soil and pots for TPS transplants.
Life starts and ends with the soil – the same is true with the potato life cycle. Fortunately, potato seeds take root in your basic potting soil or seed starting medium.
Transplanting Success: Young potato seedlings grown from true seed recently transplanted to potting soil medium.
Watching ‘Cindy’ Grow: TW54 Time lapse potato phenology’
Transplanting into the Field: Your potatoes will be ready for transplant into the field about 6-8 weeks from seeding. Since potato plants from TPS produce only one stem, unlike tuber-derived plants which will produce several, they should be planted into warm, well-prepared soil and kept well-weeded.
Now it’s your turn!
Whatever propagation system you choose to utilize, we hope that you too will find success and fun growing potatoes from true seed in nursery beds or potting trays and transplanting seedlings into your fields.
From there the possibilities are endless. We can start to observe and select for desirable traits for organic production such as early vine vigor, leafhopper tolerance and resistance to tuber defect diseases, as well as playing with colors, flavors and other qualities that we know work for our markets, our soils, and our farm systems.
The importance of locally responsive seed system for farmers is evident. As more varieties are discovered, we have the opportunity to collaborate and work in partnership with researchers, suppliers, and our soils to cross-pollinate and dissolve boundaries that in the past were prohibitive for farmers to access, creating a reliance on outside inputs and never really knowing if the varieties you need will be there next year. As a farmer, being invited to experiment with cultivating my own varieties from seed that I can save is food security I can ‘seed’ bank on.
Contact Ruth if you are interested in participating crossing potato varieties.
Whether you save your own seed potatoes or buy them, producing a vigorous crop depends on making sure your seed potatoes are as healthy as possible when they hit the dirt. But what does healthy mean for a potato? A couple of weeks ago, we talked about the importance of having low disease levels in your seed potatoes – a goal you can achieve by sourcing certified seed potatoes. Today, Erin will share what she’s learned about storing and preparing seed potatoes so they are ready to grow, and grow fast, as soon as they’re planted.
Sprouty seed potatoes:
I was sorting through my crude potato storage set-up in the basement, groping around for a handful of potatoes to bake for dinner –comfort food for a cold early March evening. Some potatoes I pulled from the bin revealed compact little green sprouts, others exhibited spindly white stems reaching upward, while a few remained solid, ‘eyes closed’ still in dormancy. I started to wonder what causes potatoes to sprout and break dormancy? Do I need to re-work my storage set-up? What might I do to influence health and vigor of potatoes? What is the proper technique for encouraging potatoes to sprout? Here are a few tips I learned from Ruth and on-line, to ensure a full life when it comes to storing and caretaking your ‘aging spuds’.
Tips for ensuring proper storage for potato seed pieces:
Potatoes start aging as soon as they form on the parent plant – even before they are harvested! One of our roles as farmers is to slow down the spiral to the compost heap and keep our produce fresh, tasty, and nutritionally dense until it reaches our forks – or in the case of seed potatoes, until they return to the soil. We can do this mechanically by regulating temperature, humidity and air circulation. Potatoes, by nature of physiology, tend to live a longer life than most other vegetables, post harvest. In storage, tubers are metabolically active, using the carbohydrates packed into them to produce energy, thus consuming oxygen and releasing carbon dioxide, water and heat. Aging is, in part, a measure of how fast the tubers are going through their resources. Keeping temperatures low, humidity high (90-95%), and air circulating will help to slow down the aging process.
For potatoes that are destined for the plate, storage at 40-45 F will keep them fresh and nutrient-packed. Seed potatoes need a deeper sleep, and are generally stored at 34-38 F. However, if you just received your seed spuds in the mail, it’s ideal to store them at 50 – 55 F with high humidity for a week or two. In these conditions, potatoes will go through an active healing process, creating a layer of suberized skin – a kind of scar tissue – to repair cuts and bruises that might have occurred during shipping. Of course, it’s always good to take a look at your seed potatoes when they arrive. Especially if they were handled roughly in shipping, this is the time that rot problems might emerge. Then, if there are still a couple of months till planting, it’s best to cool them down to 34-38 F and let them get back to sleep.
As tubers age, they come closer to breaking dormancy and sprouting – signalling that they are ready to produce the next generation of plants.Young tubers will have a single sprout, or maybe two, at the bud end. More sprouts will form as the seed reaches middle age, and if you have bushy sprouts forming, you have old seed. If your seed is forming tiny tubers on its sprouts, sadly it has given up on ever seeing soil and is unlikely to produce vines at all. Tuber physiological age is in part dictated by variety – some varieties simply have a longer dormant period than others. Field conditions experienced by the parent plants also impact the aging process – more stress means ‘older’ tubers. I find it fascinating that last year’s wet June and droughty July might have played a role in early sprouting Red Maria tubers in the root cellar.
Middle-aged and old tubers are ready to grow – so they will emerge more quickly than young seed. More sprouts ‘eyeing’ a break in dormancy equates to more stems, but each with less vigor – which then leads to smaller tubers, but more of them. Younger seed tubers? You’ll see slower emergence, few but vigorous stems, and fewer but larger taters. If your customers enjoy smaller spuds at the market and in their CSA boxes, planting ‘aged potatoes’ works to your advantage (though you can also manipulate size by harvest timing and spacing tubers closer together). The key is to optimize your storage conditions and learn, through field and storage observation and good record keeping, what to look for in a good seed piece.
As farmers (and caretakers of the tuber aging process) our role is to know when to intervene. Inevitably, your tubers need to grow up as you don’t want your seed potatoes to linger too long in dormancy and risk losing your planting window. You can speed up the aging process with a little preparation prior to planting. If you’re not sure how old your seed tubers are, just take a handful out of storage and let them sit at 60-70 F. After about a week, take a look and see if you have any sprouts – and how many. If there are no sprouts, your tubers are still dormant and will need some waking up before planting.
You’ve got to be Chitting Me
I never knew that it would take me 36 years of living on this planet before I finally discovered how to chit. Potatoes that is. One way to encourage varieties which are slow to break dormancy is to greensprout, or chit potatoes. Greensprouting seed potatoes will hasten emergence and overall development, leading to an earlier harvest. It’s a simple process, so don’t be like me and wait 36 years before chitting. Rather consider starting this season and follow these basic steps:
1. If your seed potatoes are still dormant, warm them to ~70 F for a week to help break dormancy.
2. Let the tubers cool down to 50-55 F, and keep them in low light for 2-4 weeks.
All of the tubers need light exposure. Depending on how many tubers you want to greensprout, you may be able to simply set them in a shallow tray, or you may need to build or buy many trays and stack them so that light can penetrate. In Europe, where greensprouting is a common practice, commercial setups with hanging bags can be purchased. For her trials of greensprouting, Ruth has taken mesh bags and sewn channels into them, filled them with potatoes and hung them from racks in a lighted basement.
After a week or two, you will start to see stubby green sprouts. These are strong, hardy sprouts that will not break off easily. And they will burst into life when you plant!
Pre-cutting is another way to age young seed potatoes. Not all seed potatoes should be pre-cut – only seed of young or middle physiological age. Pre-cutting can improve emergence, and, since planting is a busy time, it can also improve labor flow on the farm. The steps are:
1. Warm seed to 50-55 F, and cut into 1.5-2 oz seedpieces.
2. Allow to heal for 2-7 days with high humidity.
3. Cool to 45-50 F and hold for 1-6 weeks.
4. Warm to 50-55 F before planting.
If your seed doesn’t need any waking up, it’s still good to warm it to 50-55 F at least a week before planting, and to cut no less than 2 days before planting. Ideally the soil and the seedpiece will be at about the same temperature when you plant.
Storage, seed piece size and physiological age of the seed piece are just a few factors that determine the final yield. We’ll delve deeper into other factors in preparation for this season’s planting that influence yield such as soil conditions, accuracy of the planter, and diseases in future blog posts.
In the interim, we’d love to hear from you. What challenges have you encountered in storage? Are there discoveries you’d like to share from your experiences aging potatoes? Are there advantages and disadvantages to chitting that you’d like to add? To chit or not to chit – is that indeed the question? I’ll let you know in another 36 years.
The MOSES Organic Farming Conference was, once again, inspiring! It was wonderful to hear from so many experienced and insightful presenters, to catch up with old friends and make some new ones. On the last day, I was chatting with a farmer friend and we commented on how everyone looked both exhausted and extremely happy – which is exactly how both of us looked and felt.
Before the conference I attended the Organic Agriculture Research Symposium, a 2 day meeting of organic researchers from across the US. We heard some of the latest research into organic systems, including breeding for locally adapted varieties. There were presentations on carrot and sweet corn breeding projects, and I had the opportunity to present my work on potato variety selection for organic systems. The presentations will be made available online at eOrganic. At the conference there was a lot of discussion of farmer-led breeding of crop and vegetable varieties for organic systems. Theresa Podoll of Prairie Road Organic Seed gave a wonderful presentation covering the efforts of many farmer-led and farmer-researcher partnerships, including their own on-farm breeding. Greg Reynolds of Riverbend Farm, the MOSES Organic Farmer of the Year, encouraged farmers to start selecting locally adapted varieties on their own farm, saying “you don’t have to be serious about it – it’s fun!” I came away inspired, encouraged, and even more committed to the task of preserving and sharing the genetic diversity of our crop plants.
For those of you who are newly visiting the Organic Potato blog after the potato production workshop that Doug Rouse and I gave – welcome! Please look around in the sidebars for links to resources and read through the blog archives. Consider this an open invitation to leave comments, questions and suggestions below. Or use the “Contact us” link to send me an inquiry. I am taking a few days of rest, but will be back later in the week to respond. In the meanwhile, welcome! And please join the conversation.