Lettuce, Lactuca sativa
Lettuce may not seem like one of those life saving must-have crops, give me a potato over a lettuce leaf any ‘survival’ day, but it still deserves a place in our gardens. Lettuce is healthy to eat, easy to grow and easy to save seed. It’s also high on my mind at the moment because I have some super lettuce in my garden at the moment (surviving multiple teen-fahrenheit temperatures with no protection). They say lettuce is lightly frost tolerant, but we’re talking about an entire species here, and there seems to be a few tough nuts in the crowd. The variety in question is Tango, and I’ll certainly be saving seeds from the surviving plants come spring.
Lettuce is best planted in spring, late summer and fall. Avoid the deep summer months because lettuce is known for it’s quick-bolting nature. Bolting describes the action of a plant sending up a flower stalk in readiness for reproduction. At this stage the lettuce leaves turn bitter and new production will be slow or not at all. Most people pull up the plant once it bolts, making space to grow something else.
Lettuce seeds are extremely small. A single packet averages five hundred seeds, or each composite flower can produce 15-25 seeds. Having that many seeds allows you to plant little and often. Sow a row or small patch every 7 to 10 days throughout spring or fall. This successive method offers a continual harvest; you are likely to have some lettuce plants reaching maturity while other plants are bolting and others are germinating. I usually sow quite densely, broadcasting the seeds in the area I want to grow. I will thin by harvesting small plants for baby leaves, leaving other plants to mature and fill the space.
My Mum likes to grow lettuce bowls (a shallow pot, perhaps 16” in diameter) and harvest with a method she calls cut and come again. She sows densely and gives the bowl a haircut once the leaves are 4-6” tall. If you cut about 1” from the soil line the bowl will re-grow another crop. You can do this 2 or 3 times before giving the bowl to the chickens to clean up.
Lettuce seeds can germinate in temperatures as low as 40F (although their optimal soil temperature is around 65F). The germination process is light sensitive, so whether direct seeing outside, or starting the seeds in pots inside, make sure you don’t plant too deep: No more than ⅛”.
Heat Tolerant Lettuce
If trying to grow lettuce into the summer, you’ll have more success if you choose heat tolerant varieties and prevent the plant from becoming stressed. Some favorite varieties I like to plant in late spring are Jericho, Parris Island Romaine and Black Seeded Simpson. You can reduce the stress factor with deep watering and shade cloth (or natural shade from something like a large-leafed squash). Remember, lettuce seeds won’t germinate much above 80F, a thermo-inhibition hormone prevents germination to protect the seed from trying to grow in unfavorable conditions. Even heat resistant lettuces will still bolt, you’re just buying yourself an extra few weeks of production.
Cold Tolerant Lettuce
If trying to grow lettuce into the winter, variety selection and protection are also important. I’ve had good results with Winter Density and Tango as really cold-hardy varieties, but row covers, low tunnels, cold frames and high tunnels can all provide frost protection that will allow your lettuce to stay alive during the coldest nights. Heat is an important growth factor, but so is daylight length. So, during winter the lettuce loses what it needs to keep growing, or regrow (this can mean dormancy, not death). Cut and come again becomes cut and wait and long time.
Saving Lettuce Seed
Lettuce produces perfect self-pollinating flowers which makes seed saving easy. As little as 10 ft of separation between lettuce varieties can prevent cross-pollination (more on this issue in later articles, where it’ll become more of an important consideration). Just let a few bolting plants continue to do their thing! Lettuce produces lots of tight clusters of little yellow flowers. The flowers will die and in place you’ll see what looks like small white pom-poms (technically pappuses). Pluck these pappuses from the dead flower and you’ll find they are attached to a collection of seeds. The pappuses are the mechanism for seed dispersal. They will float and blow on the wind.
Harvesting seeds from a range of plants by hand is a good method because the plant flowers and sets seed over a period of time. Waiting for all the seeds to be ready runs the risk of ruining the entire crop with storms and rain. Chopping the entire stalk is an option if a good portion of the seeds have formed. Place the stalk and seed head upside down in a brown paper bag to finish drying and maturing. Poke holes in the bag for airflow and leave it somewhere cool and dry (carport, basement, unheated room).
Cleaning the seeds can be as simple as pulling the seeds from the fluffy pappuses. Separating the non-seed detritus is important to prevent possible pathogens contaminating your seeds. Good storage conditions are dry, dark and cool. I place mine in sealed jars with a silica gel pack to deal with trace moisture. I store them in the basement or refrigerator. Under good conditions, the seeds can remain viable for up to six years.
One of the magical things about seed saving is the opportunity for varietal improvement. Save and replant seeds from the lettuce plants which bolt last in the summer months, thereby selecting for heat resistance. Save seeds from any lettuce plants that survive the winter and flower in spring, thereby selecting for cold tolerance. With traditional season extension methods and variety improvements, there is no reason you can’t be growing lettuce almost year round.