Is your lettuce yielding more flowers and stems than crisp leaves? That’s a sign that your plant has bolted, which is the stage where the lettuce begins to divert all its energy into producing flowers and seeds instead of leaves.
The dilemma still perplexes the experts, who can’t seem to agree whether it’s possible to prevent bolting or not.
However, there are some things you can do to postpone it, such as early planting, vernalization, and growing varieties that bolt late.
Let’s dive in!
Planting As Early As Possible
Bolting lettuce isn’t always a terrible thing, especially if you want to gather some seeds for the next season.
But if you’re growing this veg for salads, you don’t want to let each plant flower prematurely or your lettuce will be bitter.
One of the best ways to avoid this is planting lettuce early in the season. This veg is a cool-season crop and hot weather can make it bolt.
Therefore, plant it some time from March to July, depending on your climate. You can even start it indoors in February and transplant it once the weather warms up a bit.
Vernalization
Long days and hot temperatures are common causes of lettuce bolting, but they’re not the only ones.
This veg belongs to the aster family and when their ungerminated seeds are exposed to temperatures below 68°F, they are more likely to bolt as mature plants.
Vernalization is an issue if your lettuce self-seeds in the fall, overwinters in the soil, and then grows as the weather warms up.
The key to avoiding this would be to harvest the seeds before they fall to the ground and store them in a warmer location before planting.
Additionally, if you grow your lettuce in a more controlled environment, such as indoors, in a grow tent, or a greenhouse, you can try and mimic its ideal growing conditions.
One research showed that night chilling and end-of-day light treatment inhibit stem elongation and, as a result, bolting. (1)
These conditions resemble those most gardens experience in spring, so it’s best to plant your lettuce in late winter or early spring to avoid bolting.
Grow Late-Bolting Lettuce
Premature flowering is one of the main causes of bitter lettuce. And since no one wants to buy or eat their own bitter lettuce, nurseries have come up with late-bolting varieties which overcome this issue.
You can find them labeled as heat tolerant when buying seed packets, seedlings, or ordering them online.
If you want a type that resists bolting very well, look for Batavia lettuce. Nevada, Rouge Grenobloise, Tahoe, and Sierra all belong to the Batavia variety and are slow to bolt and incredibly pest-resistant.
You can also grow some other varieties, such as Black Seeded Simpson, Simpson’s Elite, etc.
Succession planting – sowing seeds over a period of a few days or weeks instead of all in one go – can help you reduce the risk of bolting.
Harvesting the outer leaves first, planting lettuce where it gets light shade during the hottest time of the day, and making sure it’s moisturized can slow down bolting.
And if you’re still left with bitter and bolted lettuce after all this trouble, you can always compost the leaves and use the experience you got for next year’s planting season.
You can also add bitter lettuce to stews and soups that are a bit more sweet and it will help balance the flavors.
References:
1. Okuda, N., Miya, Y., Yanagi, T., & Yamaguchi, K. (2017). Effects of End of Day Lighting after Night Chilling Treatment on Growth and Development of Lettuce. Environmental Control in Biology.