Bolting occurs when a crop prematurely grows flower stalks and produces seeds, preventing the plant from bearing a vigorous harvest. The vegetable plant becomes elongated starts flowering and producing seeds before maturity. Bolting redistributes a plant’s energy away from the leaves and roots to produce seeds and a flowering stem. Bolting signals the end of new leaf growth.
Vegetables bolt in response to stress, prompting them to begin the reproduction process. Conditions that cause bolting include increased day length, high soil temperatures, and root stress. Due to increased day length, bolting happens because most popular garden vegetables grow in the early spring. As summer approaches, the days get longer, and sun exposure increases potentially damaging garden plants. This can be an issue if you plant your seeds too late in the spring.
Warm soil temperatures cause stress for crops, triggering them to begin seed and flower production. While this process isn’t an issue when it occurs on schedule late in the plant’s life cycle, bolting often occurs during unnaturally hot weather or if you plant crops too late into the growing season.
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Bolting caused by root stress typically happens when you disturb a plant’s root system by transplanting or if your plant runs out of growing space in a small container.
Once a plant begins to bolt, the process is irreversible. The plant’s leaves develop a bitter taste and might even grow small hairs that make them unpalatable. Bolting can be prevented by; Planting bolt-resistant varieties labeled “bolt-resistant” or “slow bolting” as these seeds are specifically developed to resist conditions that cause bolting. For example, when growing onions, look for heat-treated onion sets; these onions can withstand high temperatures, and they’re much less likely to develop flower buds in warm weather.
Reduce soil temperatures by covering the soil with a layer of mulch. Plants with heat-sensitive roots, such as broccoli, cauliflower, and cilantro, are susceptible to bolting when the soil temperatures are heating the roots. A layer of mulch keeps the soil cool and moist.
Set your vegetables during a cool season. Depending on your local climate, an early spring planting time may still be quite warm. Alternatively, try growing spring vegetables in the fall, when unnaturally warm temperatures are less likely. Brassicas like kale, cabbage, and bok choy can all grow in spring or fall. Provide shade for your cold-weather crops.
If you live in a hot-weather climate, provide shade for cool-season crops like radishes, lettuce, and spinach. Even vegetables that grow in full sun conditions can bolt if the weather is too warm. You can provide natural shade for these crops by planting them near taller plants like corn or setting up shade cloth coverings during the extra-hot midday temperatures.
One factor that leads to vegetable bolting is the drier conditions that occur in summer after the spring rains have ended. Allowing the soil to dry out around spring vegetables will cause them to bolt more quickly. Ensure your garden is getting at least one inch of water per week, more if you have sandy soil. If the weather suddenly gets hot, make sure you go out and soak the beds where spring vegetables grow so they don’t have to deal with extra stress.
Plants prone to bolting due to root stress such as carrots, turnips, beetroot, radishes, and many herbs grow best when you direct sow them outdoors, rather than transplanting. Plants in the carrot family tend to develop long, tapered, carrot-like taproots. When these plants are disturbed by transplanting, the plants respond to the stress by bolting.
These plants include dill, caraway, cumin, cilantro, and others. It’s generally better to direct-sow these plants instead of trying to transplant them. This allows their root systems to develop without interruption. If you treat your crops with fertilizer, ensure the fertilizer is tailored to grow leaves and stems instead of one that encourages flower growth. Fertilizers that benefit green growth often have higher nitrogen content.
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