Is a scorching summer the time to talk about growing lettuce? Lettuce is a cool-weather crop, but it’s an easy nutritious food when the weather is right. Can we grow lettuce in summer? We can, but with more attentive care than during early spring.
First of all, during seed selection we have to pay close attention to the variety’s growth preference. Some varieties are said to be slow-bolting, and those are the varieties we may be able to grow in summer. Bolting means that heat has risen to the point and duration when the plant goes to flower (then seeds). The foliage, the part we eat, turns bitter as this happens. “Slow-bolting” means weather has to get hot and stay hot for a time for the plant to begin to bolt to flower.
Some say the lettuces known as Batavian lettuce varieties are best summer lettuces. Batavia was the name of the capital of the Dutch East Indies, now called Jakarta — obviously a tropical climate. That’s the wrong Batavia, however. The Dutch, known to be experts at horticulture, are the source of the “Batavian lettuces.” Batavia was the Latin name of the Netherlands, or low countries, in Roman times and the late 18th century. When they sold to French consumers, these lettuces were known as “Batavian lettuces.” That lettuce tends to be loose-leafed and crisp, a little tough too, although slow to bolt.
We can fool lettuce plants to some extent about temperature by introducing shade to the plants, under an elevated shade tent or by growing lettuce in containers that can be moved to a shady location, or even by planting lettuce in a partly shady spot to begin with. They won’t thrive in deep shade, but dappled shade or full sun exposure for a few hours per day works. Then, with leaf lettuces, for instance, you may harvest the outer leaves, leaving the growing center intact, before the plant resets itself and begins to put up flower stalks. (That’s the best way to harvest spinach and Swiss chard too).
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“Full sun” for lettuce can be just a few hours each day. The variety known as Jericho was bred in Israeli deserts to withstand heat. I’ve not had very good luck with it here, however, but some folks have.
Varieties I’ve grown that appeared to be slow to bolt and haven’t turned bitter are Garden Babies, Italienischer and Mantilia. Garden Babies are soft head lettuces, what some call “butter lettuces.” They didn’t turn bitter even as they began to develop flower heads. Italienischer is a very large leaf lettuce, growing somewhat similar to Romaine, but with is a looser head. Leaves of Italienischer are crisp and noticeably tougher than those of butter lettuce. Years ago I planted it in spring, and then let it go to seed over summer, harvesting the stalks with seeds in September. I keep seedy lettuce stalks in paper shopping bags, harvesting a few seeds when I need them. Italienischer seed is available from Territorial Seed Company.
Many years ago I was introduced to Mantilia lettuce by a Master Gardener colleague, the late Don Wootton. He gave each of us a four-inch pot full of tiny lettuce seedlings. I transplanted a few, leaving the rest in the pot, keeping the pot watered. Every few weeks I transplanted a few more from that pot, and we enjoyed lettuce salads all summer from our garden. Mantilia is a sweet tender lettuce, and it’s never been bitter. Wootton apparently got Mantilia seeds from Renee Shepherd’s catalog, but now it’s available from the public Seed Savers Exchange catalog. Shepherd no longer publishes a catalog, but is still selecting wonderful varieties of vegetables, flowers and herbs for home gardens. Her seeds, including seeds for Garden Babies lettuce, are available on Renee’s Garden seed racks, such as that at Edwards Greenhouse,
The usual advice is to sow lettuce seeds every two weeks. I’ve found that results in a glut of more lettuce than two can consume, but I haven’t got the timing worked out perfectly yet. One of the problems is that some varieties take longer to harvestable size than others. Many leaf lettuces are capable of being harvested (cut about an inch to inch and a half above soil surface), left to re-grow and harvested again and again. Regrowth three times is about the maximum for any of these “cut-and-come-again” varieties. One old reliable variety is Black Seeded Simpson.
Lettuce seed tapes are available, but they’re costly and don’t always work as the gardener prefers. I still prefer to seed lettuce indoors, transplanting to larger containers, and later transplanting outdoors in the spacing I prefer so I don’t have to thin seedlings. Supposedly pre-spaced seeds are the main advantage to seed tapes.
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