Mid-summer has finally caught up with my spring garden. The lettuce I set out in early May has matured. We’ve eaten dozens of salads and shared the bounty with friends. The few heads that remain are beginning to stretch upwards. Sweet leaves are turning bitter. When the plants we grow for greens decide to grow flowers instead of leaves, we all that “bolting.”

I was hoping to stretch my lettuce harvest one more week, but a hail storm this afternoon sealed the fate of my spring lettuce patch. The chickens don’t give a cluck about the bitterness, so the now-shredded leaves are all theirs.

Some varieties last longer in the garden than others, but even so, lettuce is very difficult to grow during these long days and high temperatures. Our previously well-behaved plants are feeling the heat, and they’re ready to party.

It’s not the gardener’s fault—lettuce is genetically programmed to reproduce as the days grow longer. It’s all chemistry. As sunlight hits the leaves, they send a chemical signal to the growing tip of the stem. When the stem receives enough of these signals, it starts to elongate. The plant goes into flowering mode., and there’s no holding it back.

And, while heat alone won’t cause the plants to bloom, it accelerates the whole chemical process. It’s too bad that long days and hot weather go hand in hand.

We can delay the process a bit by harvesting the outer leaves and leaving the inner ones to grow. Since the big, outer leaves have been exposed to more hours of daylight, removing them slows down the production of those chemical signals. I’ve had shade cloth* over my bed for the last month, and that helps too. But eventually, it all catches up and our salad days are over.

It’s now the middle of July, and the days are beginning to get shorter again. This is the time to start another round of lettuce seedlings. Since lettuce prefers cool weather, it’s probably best to germinate the seeds indoors. In fact, if the seeds get too hot, they go dormant. A two-week vacation in the refrigerator or freezer is then needed to reassure them that it’s all right to sprout.

Spinach, although not related to lettuce, has the same problem with bolting. Once we pass the fourteen-hours-of-sunlight mark, spinach will start its flower and seed cycle. It’s just the nature of the plant. If you were frustrated that your spring blossomed before you were tired of fresh leaves, try growing it for a fall harvest. Since the days are steadily getting shorter, fall spinach will never bolt. And since spinach is remarkably hardy, many gardeners are able to pick leaves even into the winter months.

Markets have salad makings year round, so we forget that not all crops are suited for all parts of the growing season. At our house, we eat lettuce salads in spring and fall, and feast on other vegetables in summer. My beans are finally blooming, tiny squash are growing under the big leaves, and I have enough chard to feed a vegan convention. I can afford to wait a month or two for the next round of home-grown lettuce.

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* The lettuce was puréed by the hail because I had uncovered the bed so that I could pick several heads, and I left it uncovered because it was getting soggy, needed some good air circulation, and no storms were predicted for the rest of the day. Hah.