by Bill and Mary Weaver
Denae Friedheim, interim director and farm manager of the Student Organic Farm (SOF) at Michigan State, has been experimenting with types of salad greens suited for late fall and winter harvest in the Lansing, MI area. She and other staff at the SOF have learned how to time seeding and transplanting so that farm marketers and winter CSA growers can provide fresh salad mixes for their customers straight through the winter.
Friedhiem and co-presenter, Tomm Becker of Sunseed Farm, recently shared this information on the last of the five Field Days offered by the farm this year. This field day took a “deep dive” into ways to provide fresh greens during the “shoulder seasons,” as well as greens suitable for deep winter harvest.
Having fresh-cut salad greens available, in addition to the usual winter storage vegetables, matters to your customers, Friedheim has learned. “Prior to my current position at MSU, for three years I ran a small vegetable farm and sold my produce at the Lansing-area farmers markets,” she explained.
During the shoulder season, from late October extending to mid-December, no other growers had fresh greens, although they did have a nice variety of winter storage vegetables. “Week after week, even before the market officially opened, the customers lined up at my stand, attracted by our fresh greens. We often sold out of greens before the market opened. The customers who were lined up for the greens also bought their week’s supply of garlic, onions and winter storage vegetables from us as well.
“If you have a CSA, the fresh greens can also be an important consideration. You don’t want your CSA customers to be getting thoroughly bored with the stored vegetables you’re offering them, right when you’re about to ask them to renew for the next season,” said Friedhiem.
The farm staff carefully schedules seeding dates and transplanting times months in advance, so they will have hoop houses filled with fresh greens during the late fall/early winter shoulder season; through deep winter, and also for the late winter/early spring shoulder season.
Scheduling those plantings does take some calendar-watching and juggling of other jobs at busy times of year. “For example, we seed our winter hoophouse kale in July, right in the middle of the typical July weeding frenzy on an organic farm. For us, this seeding is top priority.”
Attendees commented that knowing both the SOF’s and Sunseed Farm’s seeding and transplanting dates for various shoulder season and winter-harvested salad crops was very helpful.
“We also recommend later succession plantings in hoop houses of salad turnips, radishes and several types of annuals/biennials such as parsley, cilantro and green onions. In our bigger hoop houses, perennials such as rosemary, sage and thyme do fine.”
A lot of growers are nervous about investing the money in hoop houses or high or half-high tunnels. “They can pay for themselves very quickly,” she advised. “If you don’t have an ideal place to put them, although I would generally recommend putting your hoop houses on the least shaded spots with the greatest exposure to light, simply having a covered space can extend the season enough to justify some expense. For example, to use the only land available at the SOF to expand our hoophouses, we had to orient our new houses north/south. Those greenhouses paid for themselves in six months, despite their limitations. We then made really good use of some of them that spring and summer to produce fresh ginger and strawberries.”
Friedheim and staff have learned that some salad mix ingredients do better than others in the low light and cold temperatures of winter. “We’ve learned not to plant green lettuce, especially flat green leaf lettuce, for our winter salad mixes,” she explained. “It gets slimy, mats down on itself and molds. The only lettuce variety we grow for winter is red oak leaf. The red pigmentation and the curly/savoyed leaves seem to be protective with this variety.”
For other salad greens to accompany the red oak leaf lettuce, the SOF now grows several varieties of baby leaf kale, mustard, chard and beet greens. “We grow yukina savoy, mizuna, Red Russian kale, purple mustard, baby leaf orange chard, ruby red chard and Early Wonder Tall Top beet greens. For head lettuce until mid-December, we stick with Magenta and similar red varieties. Some Romaine varieties also finish well at this time of year.”
For greens to harvest in the low light and intense cold of January and February, the SOF grows Asian greens in three types: Bok choy, tatsoi and komatsuna. These will continue to grow and produce fresh leaves when other greens have hunkered down and quit. “We try to distribute tatsoi first, because it doesn’t tolerate deep cold. Bok Choy is the second-most cold hardy. The real star in deep winter is komatsuna,” said Friedheim.
“By late February, parsley, green onions, kale and spinach start to regrow, and we start transplanting new head lettuce plants and direct-seeding turnips and radishes again,” she said.
Students plant kale at MSU’s Student Organic Farm four times a year. “In addition to seeding kale in July for winter harvest, we also transplant our fall kale crop into the field in July.” The next kale planting is for the spring shoulder season, planted in February or sometimes early March. “If you plant chard and collard greens at the same time, you can have a variety of greens in very early spring,” she said.
Once these plants get bigger, put a shade cloth on the hoop house. That will keep them cool, and will give you an extended harvest period. The fourth kale planting at the SOF is made outdoors in spring.
“Year-round spinach is in its own special category,” continued Friedheim. “Look for a variety that tolerates heat for spring and summer harvest. For us, Winter Bloomsdale does the best through the winter, but if you have problems with downy mildew, you may need to do some experimenting.” Eighteen strains of downy mildew have now been identified, but not all resistant spinach varieties are necessarily resistant to all 18 strains. Choosing varieties can require experimentation.
The Student Organic Farm will be experimenting with exposing spinach to floodlights briefly in the middle of the night this year, to try to break downy mildew’s growth cycle. “Our production manager did some research and found that downy mildew needs a certain period of unbroken darkness to thrive and reproduce. We’re hoping if we briefly break that dark period with very bright lights, it may help to control the disease. Oxidate is a sanitizer you can spray on the leaves. It will kill downy mildew, but it also kills other microbes that compete with downy mildew,” she said.
Downy mildew persists in the soil, so you need a good crop rotation to combat it. In a hoop house, rotations can take place much more quickly than on open ground, if you grow year-round. “Each time you plant a hoop house in a different plant family — two to three times a year, probably — that is a crop rotation. So, if at the end of a crop of spinach, you plant tomatoes, followed by kale, then perhaps cucumbers, none of which are in spinach’s plant family, when you plant the same ground in spinach the next winter, you could have accomplished enough rotations to break the spinach downy mildew life cycle.”
Winter-long high tunnel salad mixes in Michigan
by Bill and Mary Weaver