Winter lettuce and other salad crops

We are feasting on our winter salad mixes now, so I decided to write a post to encourage more people to grow winter salads.

Just how viable this is for you depends on your winter climate zone and your facilities. In the coldest of places with nowhere except your kitchen or a windowsill, you can grow sprouts and microgreens.

To grow sprouts, get some organic seeds, soak them in a jar, then fit a straining lid, which can simply be a piece of fabric held in place over the open mouth of the jar with a strong rubber band, or, if using a Mason jar, the metal ring part of the lid. Drain off the extra water, then set the jar on its side, with the seeds distributed evenly along the side. Rinse and drain twice a day, until the sprouts are the size you want. Here’s a couple of websites.

See How to Grow Sprouts at Home, by Beth, or Growing Sprouts at Home, by The SproutPeople

You don’t need to follow these directions word by word, but if you do, it will work. Other methods can also work. Just be sure to rinse and to drain!

The enthusiastic author of How to Grow Microgreens, Sylvia Fountaine, lays out a 6-step process and provides a video. Microgreens are basically seedlings, with stems and green seed leaves. Sprouts are mostly root and stem, as you may have noticed.

For those wanting to grow microgreens professionally, I recommend Andrew Mefferd’s chapter in his Greenhouse and Hoophouse Grower’s Handbook.  

I wrote about our Fall Lettuce Transition in my post Preparing your Hoophouse for Fall and Winter 9/28/22 – This post includes days to germination of lettuce at various soil temperatures. Here are dates when we sow lettuce for growing in various places (not just our hoophouse).

·        For outdoor lettuce I stop sowing August 29, transplant those 9/22 and expect to harvest them 12/10 – 12/31. I add hoops and thick rowcover when it gets cold to keep it growing.

·        For winter growing in coldframes, I sow 9/1, 9/3, 9/5, 9/7, 9/9 and transplant 9/25 -10/8. Leaves from those plants can be harvested all winter until we need the cold frames to harden off spring transplants in mid-late February. We cover the coldframes with rowcover when it starts to get cold, then plastic-glazed lids as it gets colder, and quilts for really cold spells. These days we are more likely to direct sow spinach in the frames than transplant lettuce. It’s hardier and faster growing.

·        From September 11-17 we sow lettuce every other day in our outdoor nursery bed, to transplant in our unheated greenhouse (double glass windows, solid north wall, rarely freezes in there). We harvest those lettuces by the leaf all winter until we need to dig out the compost they are growing in to fill our seed flats in early February.

·        On September 15 and 24 we sow lettuce outdoors in a nursery bed, to transplant in our hoophouse 10/15 and 10/24. Those lettuces will feed us all winter, 11/16-3/1, if we simply harvest the outer leaves, rather than cut the head.

·        On October 23 we start sowing lettuce mix in the hoophouse. We sow successions of baby lettuce mix directly in the soil 10/24, 12/31, 2/1, 2/15. The last one, on 15 February, will be for harvest starting mid-March, and ending in May when it gets too hot. By then we should be happily harvesting juicy lettuce heads outdoors and will have lost interest in the lettuce mix. We like Fedco’s 2981LO Lettuce Mix OG or Johnny’s Allstar Gourmet Lettuce Mix #2301. For those with challenging growing conditions, both companies offer other specialized selected mixes. 1 oz (28gm) of seed sows about 600 ft, (200m) 

·        We sow “filler leaf lettuces” in our hoophouse 10/23, and 11/9, to use for gap filling (replacing casualties). 1/25 is our last date for filling any gaps in the hoophouse beds with lettuce plants. After that, we fill all gaps with spinach plants.

·        So, we have different “stop-dates” for the different types and locations, but no complete Lettuce Stop-date.

o   8/29 Last date for sowing for outdoor row-covered lettuce

o   9/9 last date for sowing to transplant in coldframes

o   9/21 last date for sowing for planting in an unheated greenhouse.

o   9/24 last date for sowing for planting into a double-layered hoophouse

o   11/9 last date for sowing “filler leaf lettuces”

o   2/15 last date for sowing baby lettuce mix in the hoophouse.

How should people not in central Virginia calculate their own stop dates? Using the same numbers as above for the various types and locations:

1. ​Figure out how late in the year it’s worth having lettuces outdoors. When does the temperature drop to 20°F (-7°C)? Stop sowing for outdoors 3-4 months before then. (Our 8/29 sowing is harvested by 12/31, but our 8/20 sowing is harvested by 11/25). It’s worth experimenting to find which date works best. Outdoors, I have found that lettuce may survive an occasional dip to 10°F (-12°C) with good rowcover. Consult your Extension Service and the website WeatherSpark.com. Fill in your location and look at pages of useful info about the weather where you are.
2. Figure when your coldframes get down to say 15°F (-9°C). This might be when the outdoor night-time low is 10°F (-12°C), lower if you have a well-insulated coldframe. We have some old quilts to roll on top of our coldframe on nights below 15°F (-9°C). Perhaps lettuce won’t make it all the way through winter in a coldframe in your climate. If so, be prepared to clear the plants when it gets too cold. Calculate back to figure when to sow – allow 4 months to get full sized lettuces.
3. Figure when your solar double-paned-glass and masonry wall greenhouse gets down to ° (-9°C), or add a small heater with a thermostat to keep it warmer than that. Calculate back to the sowing date, allowing for the fact that plants grow quicker in a greenhouse than outdoors or in coldframes. Maybe allow 3 months.

   

4. As far as daylight goes, on 9/24 everyone everywhere is pretty much getting the same amount wherever we live. With a hoophouse, the goal is to grow plants to harvestable size by the time you no longer have lettuce from outdoors (refer to #1). It probably only takes 2 months to grow a lettuce big enough for leaf harvest in a double layer hoophouse. Just be sure not to over-harvest in the winter. We have had lettuce survive a double layer hoophouse temperature of 10.4°F (-12°C) without any rowcover (sometimes called an inner tunnel), and -2.2°F (-19°C) with.
5. At this point calculations switch to what happens after the Winter Solstice. When do you plan to start harvesting your first outdoor lettuce again? Aim for a two-week overlap with both hoophouse and outdoor lettuce available in the spring. Work back from your hoophouse harvest end date to find the last worthwhile sowing date for filler lettuces. Because lettuce bolts easily when it gets warm in spring, play it cautious. We plan to start outdoors 4/15. We stop transplanting lettuce in the hoophouse 1/25, 2 1/2 months before then. Sowing filler lettuce too late is not really a problem – you can cut it as baby lettuce. But avoid transplanting it just to have it bolt.
6. If your climate is cold, or you don’t mind only getting one or two cuts from baby lettuce mix, you can carry on sowing it until the soil temperature reaches 86°F/30°C (max temp for lettuce germination). If it is warm, do be sure to water often, so the lettuce doesn’t turn bitter. Otherwise look to you first outdoor lettuce and clear the baby mix when the outdoor crop is ready.

See my post Lettuce All Year in a Changing Climate 8/31/21. It includes links to all my Lettuce of the Month series, and includes my slideshow Lettuce Year Round and our 2022 Lettuce Varieties List, to help you choose varieties we recommend for different times of year.

For ideas on mixing various crops in winter salads, see Making Salad Mix 10/31/17 and Fast Growing Vegetables 3/24/20. Winter salad mix is also known as mesclun or spring mix (even though we are growing it in the winter). Spinach and many brassicas grow faster than lettuce in cold weather, and make delicious salads.

Also, check my Asian Greens of the Month posts. This post from April 2018, includes at the end links to each of the series. Many Asian Greens make great salad crops. The frilly mustards featured in this post are a good example.

For information on the temperatures that many crops will die at from cold, see Winter Kill Temperatures 2021. I was updating this list each spring. 2022 seems to have slipped by. I don’t think I had any new information, as the winter wasn’t extreme (although we had a long and memorable power outage!).