How to Delay Bolting of Your Spring Greens

Tricking cool-season greens into believing it's not quite summer is essential to learning how to delay bolting and extend the harvest of these plants. Learn five ways you can delay bolting.

by Jessica Walliser
PHOTO: Jessica Walliser

For many farmers and gardeners the true indicator of summer’s arrival is the bolting of their cool-season greens. When the long days and warm nights of summer arrive, many leafy greens and lettuces are triggered into producing flowers and then seeds. This marks the end of their productive period as the foliage turns bitter when the flowers arrive. But, what if you could delay bolting in these plants and extend your harvest for a few more weeks? Today I share some tips on how to delay bolting in these vegetable crops.

Though it’s almost impossible to completely stop bolting, slowing down or delaying the process is possible. There are several ways to do this.

1. Provide Shade

The easiest way to delay summer bolting is to create an environment that tricks the plants into thinking it’s still spring. It could be as simple as covering cool-season greens with an umbrella or a shade cloth during the heat of the day, or perhaps it means you’ll plant a second crop of greens in a shady location, instead of in the sunny vegetable garden. Keep the plants cool by putting them in the shade and you can delay bolting by as much as a few weeks.

2. Make a Late Sowing

While most gardeners are anxious to get the garden planted as early as possible, making a second or third sowing of cool-season greens is a must for prolonging the harvest. Don’t plant all your lettuce the first week in April; instead, sow a new row of seeds every two weeks all the way through spring. The late sowings will bolt weeks behind the first sowings simply because they aren’t yet mature enough to flower.

3. Pick the Right Varieties

You can also delay bolting by making sure you choose the correct cultivars of all the cool-season greens you plant on your farm. If you know you’re going to try to extend your harvest season well into the summer, pick a cultivar that’s been bred to have delayed bolting. Look for keywords like “slow to bolt” or “long season” or “heat tolerant” or “delayed bolting” on the seed packet’s description to help you discover which varieties have an inbred resistance to bolting. Choose those selections over others that are more prone to early bolting.

4. Block the Light

Another surprising way to delay bolting is to create an artificial extended nighttime by completely blocking light from hitting the plants, starting in the evening and going through the first few hours of daylight the following morning. Cover the plants with a dark plastic pot or black storage tub to completely block out all the light to shave several hours off of the natural day length. Just remember to remove the covering for at least 8 hours per day to allow enough sunlight to reach the plants.

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5. Move Your Plants Indoors

If you’re growing your cool-season greens in containers, when the weather gets hot, move the pots indoors. When summer arrives, your home is cooler than it is outside and the light levels are a little lower, which will allow your containerized greens to produce for a bit longer.

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