Lettuce All Year in a Changing Climate

Lettuce bed in May.
Photo Wren Vile

We like to eat lettuce year round, and have put time and energy into finding the varieties and planting dates that work best here in Central Virginia, as well as how to get the best results in each season. Recently I revised our lettuce schedules, partly to take account of hotter weather arriving earlier in the year, and also to even out the harvest dates.

I have frequently written blogposts about growing lettuce. And I have a whole year of Lettuce for the Month posts. See here for the overview, or click on the month you want to know more about. These posts are mainly about our favorite varieties for each time of year.

I have a slideshow Lettuce year round  – It’s at the end of this post.

Back in 2006, I wrote Lettuce: Organic Production in Virginia for VABF. We’re now in Winter Hardiness Zone 7a. Back then we were 6b. Read this publication for details you are hazy on, but see our updated Lettuce Varieties List and Lettuce Log in this post.

Fast-growing Red Salad Bowl lettuce.
Photo Bridget Aleshire

Choose appropriate lettuce varieties for each time of year.

Sow several varieties each time to spread the harvest season and the risks of poor germination. I like to use something fast, something slow; at least one red; a romaine, a bibb and a couple of leaf types.

Consider multileaf lettuces too, Salanova and Eazyleaf brands. They are bred for uniformly small leaves, with more texture, loft and flavor than baby mixes and faster harvesting. Transplanted 6″–8″ (15-20 cm) apart they produce 40% more than baby leaf mixes. The full-size plant can be harvested as a head, providing a collection of bite-sized leaves.  Or just one side (or the outer leaves) of the plant can be cut and the plant will regrow for future harvests. Growing multileaf heads takes 55 days, compared to 30 days for baby lettuce

Red Hawk Farm hoophouse densely planted with multileaf lettuces.
Photo Pam Dawling

Our recent changes to our Lettuce Varieties List include switching over from “Early Spring” varieties to “Spring” varieties at the end of February rather than the end of March. This means we only make 3 sowings of the early spring varieties, and we need to stop buying much seed of those varieties! Next year I might even abolish that category and those early varieties to simplify life.

The spring varieties we now sow from February 28 to April 22. We used to sow these until May 15. We’re still making 5 sowings of those, but the dates have moved earlier.

On April 23 we switch over to our Summer varieties, which we make 20 sowings of, until August 14. (Buy lots of seed of those varieties!) We then switch to nine sowings of Fall varieties, until September 7.

Lettuce growing in our greenhouse in November.
Photo Wren Vile

From September 8 to the end of September we use our cold hardy varieties. These 9 sowings include those for the greenhouse and hoophouse, which will feed us all winter. 

Click to access Lettuce-Varieties-pdf.pdf

You’ll need a large screen, a magnifying glass or the ability to expand the image.

We like to grow a balance of leaf lettuce and head lettuces, and, in winter, baby lettuce mix too. We harvest the baby lettuce mix when 3″–4″ (7.5–10 cm) tall, cutting 1” (2.5 cm) above the soil. We harvest leaves from the big lettuces the rest of the time. Baby lettuce mix is very pretty, but I actually prefer the juiciness and crunch of big lettuce.

Beautiful baby lettuce mix in our hoophouse.
photo Wren Vile

Keys to year round lettuce

  • ·         Store seed in a cool, dry, dark, mouse proof place.
  • ·         Grow your lettuce quickly, for high quality and flavor, using good soil preparation and high organic matter.
  • ·         Learn the skills of lettuce germination in all weathers. Minimum soil temperature for germination is 35°F (1.6°C).  Optimum temperature range for germination is 68°F–80°F (20°C–27°C).1/4″–1/2″ (6–10 mm) deep is ideal.  Good light.
  • Watch the temperature – Germination takes 15 days at 41°F (5°C), 7 days at 50°F (10°C), 3 days at 68°F (20°C) and only 2 days at 77°F (25°C). Germination will not occur reliably at temperatures hotter than 86°F (30°C).
  • Keep watching the temperature –  Optimum growing temperatures are 60°F–65°F (15°C–18°C), Some growth occurs whenever the temperature tops 40°F (4.5°C).
  • ·         Choose good locations! We grow lettuce outside from transplants from February to December (harvesting from late April); in a solar-heated greenhouse from September to March (harvesting leaves from November) and in a solar heated hoophouse from October to April (harvesting leaves from November, and whole heads in April). We also sow baby lettuce mix in the hoophouse from October to February, for harvest multiple times from December to April.
  • ·         Use shade cloth on hoops in hot weather
  • ·         Use rowcover in cold weather, or plant in cold frames, greenhouses or hoophouses.

Lettuce under shade cloth.
Photo by Nina Gentle

Grow a consistent lettuce supply using succession crop planting

To have a continuous supply, it is important to plant frequently, at intervals adapted for the time of year. The gap between one sowing and the next gets smaller as the year progresses; the gap between one transplanting and the next does likewise. The number of days to reach transplant size dips to 21 days in the summer, then lengthens as the weather cools and the days get shorter.

We made a Lettuce Succession Crops graph using our records for sowing date and harvest start date. From this we determined the sowing dates to provide us with a fresh harvest (120 heads of lettuce, or equivalent) every single week. We made a Lettuce Log with our planned sowing, transplanting and harvest dates. This is explained in my slideshow Lettuce year round.

Lettuce Succession Crops Graph

Click to access Lettuce-Succession-Crops.pdf

Rouge d’Hiver hardy romaine lettuce.
Photo Bridget Aleshire

Recently I fine-tuned this in light of more recent records. In some cases we had been led astray by a spreadsheet date calculator that was based on 30 day months in a 360 day year! Not reality! We also had data showing that transplants were not always ready on the dates we had thought, probably due to a mistake in an earlier year when we were unable to transplant on time, and repeated the delayed date the next year. Most of the tweaking was in early and late spring, and then in August.

Click to access Lettuce-Log.pdf

Tips for growing good quality lettuce

I recommend transplanting lettuce (other than baby lettuce mix) at 4-6 true leaves (3-6 weeks of age). It is worth learning good transplanting skills, so that plants thrive, even if transplanted in mid-summer.

Water enough, with an efficient irrigation system. Water new transplants daily for the first 3 days, then every 4-7 days after that. Lettuce needs a relatively large amount of water throughout its growth.  Deeper weekly waterings equivalent to 1” (25 mm) of rain are better than frequent superficial irrigation – roots will grow deeper, giving the plant greater drought-resistance.

To make best use of space and time, plant lettuces 10-12” (25-30 cm) apart, in a hexagonal pattern. If you plant too close, you are restricting the size of the lettuce. If you plant with more space than needed, you will waste time dealing with more weeds!

Flats of lettuce transplants in our cold frame in April.
Photo Pam Dawling

Transplanting gets a head start on weed control, which is important from planting to a couple of weeks before harvest. Don’t waste time hoeing lettuce you will be harvesting next week. I generally find that if I hoe once, a couple of weeks after transplanting, that is all the weed control I need at the fast-growing time of year. We like the stirrup, or scuffle, hoes, which are safer in the hands of novices than sharp edged hoes, because the blade is in a closed loop.

Some growers use black plastic mulch, but I hate filling the world with single use plastic, so we don’t do that. Some others use landscape fabric with melted holes at the right spacing. I used this for strawberries and liked it. I’m not sure I’d find it worthwhile for fast-growing lettuce. No-till growers can transplant into mulch, first making what we call “nests” at the appropriate measured spacing. It’s tempting to skip the measuring, but if you drift from a 12” (30 cm) spacing to a 15” (38 cm) spacing, you will end up with fewer lettuces!

For those who like to direct sow lettuce, you could prepare the bed, let it rest for a week (watering it), then flame or lightly hoe the surface before sowing to remove a flush of weeds.

Lettuce seedlings for transplanting later. Photo Pam Dawling

Bolting and/or bitterness are more likely with under-watering, long days, mature plants, poor soil, crowding, high temperatures, and vernalization—once the stems are thicker than 1/4″ (6 mm), if plants suffer 2 weeks of temperatures below 50°F (10°C), followed by a rapid warm-up.

Bolting lettuce in July
Photo Alexis Yamashita

Deal promptly with pests and diseases. Aphids, cutworms, slugs, rabbits, groundhogs and deer all like lettuce as much as we do. If you find your lettuces melting down with fungal diseases, you can, of course, commit to better crop rotation. You can also consider solarizing beds for next year’s lettuce. You need a minimum of 6 hot weeks in which to cook the soil-borne disease spores by covering the prepared beds tightly with clear plastic. Old hoophouse plastic is ideal – construction plastic does not have the UV inhibitors that prevent the plastic shattering into shards. 

More resources

Cornell has a 2016 Organic Production and IPM Guide for Lettuce 67 pages of everything you are likely to need, for growing in New York type climates, at least.

Ray Tyler at Rose Creek farm has a Lettuce Masterclass, a step-by-step blueprint to plan, grow, and sell lettuce year-round!

This slideshow is from 2019, before I made the changes I mention above.

Lettuce Year Round 60 mins

Potato yields, Salanova lettuce review, Yet more snow!

Newly emerging potato plant in the spring Credit Kathryn Simmons
Newly emerging potato plant in the spring
Credit Kathryn Simmons

After my Feed the Soil presentation at Lynchburg College on 3/16, one of the participants emailed me to ask the relative potato yields from our twice a year plantings. The question sent me back to my records. Interestingly (to me) I’d recorded yield almost every time, but never compared the two. Now I know:
15 years of records on spring plantings (mid-March) gave yield ratios from a very low 3:1 to a happy 13:1. The average was 8.2:1 and the median 8:1.
16 years of records on the mid-June planting gave yield ratios ranging from a miserable 3:1 to a high of 10.7:1. The average was 7:1, and the median the same.

We used to plant at 10″ in-row spacing and have shifted to 12″. These figures contain both, with no obvious difference.

Looking at these results points out to me an advantage of doing two plantings that I didn’t mention during my presentation: a poor spring result can be followed by a good summer result. And vice versa. The 13:1 spring result was followed by 4.8:1 in the summer. The 3:1 spring yield was followed by 7.2:1 from the June planting. Doing two plantings spreads the risk.

The questioner also asked if we get potato beetles. We do get them in the spring and spray once, occasionally twice, with Spinosad, which is organically acceptable. In the summer we get no potato beetles. I think the mulch helps. Adult potato beetles emerging from the soil have to walk to find potato plants, and I bet the mulch is very challenging!

We use the same varieties in both plantings, Red Pontiac and Kennebec. Kennebec stores better, Red Pontiac gives higher yields, but isn’t good for long term storage. That said, we recently finished eating Red Pontiacs from our October harvest. I haven’t done much research into trying other varieties because we just buy what’s available locally.The Irish Eyes catalog has descriptions of varieties better for certain conditions. Moose Tubers (Fedco Seeds) has a useful comparative chart of varieties.

Salanova Lettuce Review

My impulse buy when ordering seeds last year was the full set of Salanova Lettuce from Johnny’s. These are varieties of lettuce bred for baby salad mix. You grow them as transplanted heads, and when the head is mature you cut the whole thing and bingo – you get a bowlful of small leaves. They do not grow big leaves, just more and more small leaves. Some of them have a core which you need to cut out in order to make the leaves fall apart. Others you just cut across at the base .If you’ve ever grown Tango, you’ll now the kind of thing.  As well as being very pretty, these lettuces are said to save you time at harvesting compared to cutting along a row of baby lettuce mix. This aspect really appealed to some of our crew.

Johnny's Foundation Collection of Salanova. Photo from their catalog
Johnny’s Foundation Collection of Salanova. Photo from their catalog

Because the seed is expensive (100 pelleted seeds for $15.95), we decided to grow these for our hoophouse “filler” heads, which we transplant into gaps that happen in our beds of head and leaf lettuce. That way we’d get them at the time of year (late winter/early spring) when we grow baby lettuce mix and we could do a direct comparison.

We bought the full set, 100 seeds of the Foundation Collection (the more frilly types) and 100 seeds of the Premier Collection (the more flat and lobed types). Each collection is 25 seeds each of four varieties. We sowed each type in a 4′ seed row (seeds 2 inches apart) on 10/23. They came up well, and we transplanted them 1/2/14. We just started using them 3/20, so the jury is still out. Some unfortunately got cut before reaching full size. I’m not sure what full size is yet. Next year, I’d sow them earlier, so that the heads mature sooner. This winter has been very cold, they may have grown slower than they could have – some other seedlings are certainly slowed down.

A couple of them are exceptionally pretty. The Red Butter type has beautiful very dark red simple shaped leaves. The Red Sweet Crisp reminds me of a fine seaweed in looks – green at the base and intense dark red at the tips. The Green Sweet Crisp is surprisingly sweet, in a good way. Winter lettuce mixes are not usually crisp or sweet.

Osborne Seeds Multileaf Multi-red Lettuce. Photo from their website.
Osborne Seeds Multileaf Multi-red Lettuce. Photo from their website.

Also next year, I’d like to compare these with some “Multileaf” varieties from Osborne Seeds. They have 7 varieties, 3 green and 4 red. It took me a little while to realize “multired” was “multi-red” and not the past tense of “to multire”, a verb I was pondering the meaning of! They are $7 – $7.47 for 500 pelleted seeds. Some are back-ordered right now, but I’d want them next winter anyway. I’d also like to do a side-by-side comparison with Tango, Oscarde and Panisse which are inclined towards packing in many small leaves without further marketing.

And finally, yes, we’re expecting some more possible snow tomorrow morning. Can you believe it? Maybe we’ll just get rain.