A bed of lettuce in May. Photo by Wren Vile
When I moved to central Virginia 25 years ago, it was accepted as fact that we couldn’t grow lettuce in the summer. And we didn’t yet have a hoophouse yet, so we didn’t have lettuce in winter either. I set out to extend the lettuce seasons of fall and spring, and got them to meet, so that we can have a continuous supply of salads all year. I wrote about winter lettuce here, and I just completed a year of postings about suitable lettuce varieties for each month on my own blog Sustainable Market Farming. Here I’m going to provide a general strategy for scheduling lettuce plantings so that you have neither gluts nor gaps in your supply. This kind of scheduling is called “succession planting” and is also used for short-lived warm weather crops (think zucchini). I have a slide show on Succession Planting, which I present at some of the Mother Earth News Fairs.
Sow Several Lettuce Varieties
One simple way to extend the harvest period of each lettuce sowing is to sow several different varieties on the same day. Choose varieties with different numbers of days to maturity, including at least one fast one and one slow one. There can be quite large differences in days to maturity, for instance Buttercrunch is a small, fast, reliable green 48-day butterhead (bibb) and romaine lettuces generally take 55-58 days. Looseleaf lettuces like the 50-day Salad Bowls are a very useful lettuce type because you can harvest individual leaves off the whole row while you wait for the heads to reach full size. (Yes, you will be setting them back a bit, but there will be plenty of lettuce later and this method will give you lettuce sooner.)
Buttercrunch Bibb Lettuce. Photo by Kathleen Slattery
Choose Lettuce Varieties to Suit the Season
My second tip is to choose varieties which work well for the time of year. This will help ensure that the lettuce you plant reaches harvest in a good state. Here the Lettuce Year has 5 seasons: Early Spring: January-March; Spring: April 1-May 15; Summer: May 15-Aug 15; fall: August 15-September 7 and winter: September 8 until the end of September, when we start our break from sowing lettuce (but not our break from harvesting!) Each season has varieties which work well and others which do not. Our springs are short and quickly heat up, so we only have a small window for sowing lettuces which bolt as soon as the weather warms at all. That window closes March 31 for us, and examples include Bronze Arrow, Freckles, Merlot, Midnite Ruffles, Oscarde and Panisse. Johnny’s Selected Seeds has a head lettuce planting program with three seasons (early season, mid-season and late season) where they recommend some suitable varieties. Varieties for early spring are fast-growing. Mid-season varieties have some heat-tolerance (resistance to bolting). Their late-season varieties are chosen for disease resistance and cold tolerance.
Sow Extra Lettuce Seeds
We sow four lettuce varieties each time and I like to choose varieties that differ in color and shape. There is no reason to get bored with lettuce! We are planting 120 lettuces each week, to feed a hundred people, and it is easy for us to make four flats of 40 transplants each, allowing us extras in case something goes wrong, or it turns out that we are planting one of the longer beds that week. If we see that the following sowing has come up poorly, we might transplant more than 120, or save the leftover lettuce plants to fill out the next planting.
Lettuce Scheduling Made Easy
For a continuous supply, lettuce needs to be planted many times during the season. Typically, crops mature faster in warmer weather. So, to get harvests starting an equal number of days apart, you need to shorten the interval between one sowing date and the next as the season progresses. An easy “No Paperwork” way of finding out what the planting intervals need to be is available to those who direct sow their lettuce, or sow it outdoors in a nursery seedbed. Sow some lettuce and the day it emerges, sow some more. This method works because as the weather warms up in spring, the lettuce seed germinates faster, giving you the signal that it is time to make another sowing. Your sowing intervals get shorter, without you having to do any calculations. You do need to pay close attention, and you do need to be experienced enough to be sure that your seed will germinate. Otherwise you would just wait and wait. . .
Here is a table of soil temperature, days to emergence, and the percentage of normal seedlings you can expect. This is based on figures from Nancy Bubel in her Seed Starter’s Handbook
|
Lettuce seed days to emergence and percentage of normal seedlings at various soil temperatures |
|||||||||
|
Soil temperature |
32F 0C |
41F 5C |
50F 10C |
59F 15C |
68F 20C |
77F 25C |
86F 30C |
95F 35C |
104F 40C |
|
Days to emergence |
49 |
15 |
7 |
4 |
3 |
2 |
3 |
0 |
0 |
|
% normal seedlings |
98 |
98 |
98 |
99 |
99 |
99 |
12 |
0 |
0 |
As you can quickly realize, it’s pointless to try to germinate lettuce in soils as warm as 86F (30C). In hot weather, sow in the late afternoon or at nightfall. The cooler night-time temperatures give the seed better emergence than morning sowings.
Lettuce scheduling Made Memorable
Maybe you don’t want to be on tenterhooks watching for seeds to come up? An easy memorable sequence to follow is
• sow twice in January
• twice in February
• every 10 days in March
• every 9 days in April
• every 8 days in May
• every 6-7 days in June and July
• every 5 days in early August
• moving to every 3 days in late August
• every other day until Sept 21.
After that we make a couple of “insurance sowings” before the end of September.
New Red Fire lettuce. Photo by Bridget Aleshire
Lettuce Scheduling Made Perfect
For a customized close-fit plan for your farm, save three pieces of information for each sowing you make this year: the sowing date, the date of first harvest and the date of last worthwhile harvest. In the winter, use this information to make a graph to fine-tune your future sowing dates. In my Succession Crops slideshow I explain and show my 5-step method.
• Plot a graph for each crop, with sowing date along the horizontal (x) axis and harvest start date along the vertical (y) axis. Mark in all your data. Join with a curve.
• Mark the first possible sowing date and the harvest start date for that.
• Decide the last worthwhile harvest start date, mark that.
• Then divide the harvest period into a whole number of segments, according to how often you want a new patch.
• Figure the sowing dates needed to match your chosen harvest start dates
Don’t Stop too Soon!
At some point in the fall, you will reach a date when it’s time to stop sowing. Knowing this might save you from giving up too soon. Any lettuce sown after your stop date would make little if any growth for the winter. Lettuce can make growth whenever the temperature stays above 41F (5C), although spinach and kale grow faster at those low temperatures. Figure out when it will get too cold for lettuce growth where you are, taking any protected growing space into account.
Pam Dawling works in the vegetable gardens at Twin Oaks Community in central Virginia. She often presents workshops at MEN Fairs. Pam also writes for Growing for Market magazine. Her book, Sustainable Market Farming: Intensive Vegetable Production on a Few Acres, is available atwww.sustainablemarketfarming.com, Pam’s blog is on her website and also onfacebook.com/SustainableMarketFarming.
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