If you’ve ever gone out to your garden expecting to harvest fresh lettuce or cilantro, only to find it suddenly growing tall with flowers, you’ve seen bolting in action. This is a common issue, especially in spring and early summer, and it can make some cool season vegetables tough and bitter. While bolting is a natural part of a plant’s life cycle, there are ways to slow it down and extend your harvest. This is a picture of broccoli that has “bolted”.
What Is Bolting?
Bolting happens when a plant shifts from producing leaves, roots, or stems to focusing on flowers and seeds. You may see a burst of vertical growth, smaller leaves, and the development of flower stalks. This change is a survival strategy—when a plant senses stress, it speeds up seed production to ensure the next generation. In early spring, your cool season vegetables thrive in temps 35-65 degrees. If the temperature starts to warm up unexpectedly, or if you plant too late, you may see your plants start to bolt.
Which Vegetables Are Most Affected?
Some vegetables are more prone to bolting than others, particularly cool-season crops that struggle with rising temperatures. These include:
- Lettuce – Becomes tough and bitter once it bolts.
- Spinach – One of the fastest crops to bolt in warm weather.
- Cilantro – Often bolts quickly in spring and summer. Shown in the picture above
- Radishes – Instead of forming a crisp root, they focus on flowering.
- Bok Choy – Can bolt early if exposed to temperature swings.
- Broccoli and Cauliflower – They still produce heads, but if they bolt, they flower too soon.
- Dill and Basil – While herbs naturally flower as part of their cycle, early bolting can shorten their best harvest window.
What Causes Bolting?
Bolting is triggered by a combination of naturally occurring factors or some we create ourselves
- Warm Temperatures – Many cool-season crops start bolting when temperatures climb above 75°F.
- Longer Daylight Hours – Some plants respond to increasing daylight by switching to seed production.
- Cold Stress – Early exposure to cold temperatures can cause some plants, like spinach and cilantro, to bolt prematurely.
- Lack of Water or Nutrients – Plants under stress from drought or poor soil may bolt sooner.
How to Prevent or Slow Bolting
While you can’t stop bolting entirely, there are ways to delay it and keep your plants productive for longer.
Choose Bolt-Resistant Varieties
Many seed companies offer bolt-resistant varieties of lettuce, spinach, and cilantro that are slower to flower. These are worth considering if you live in an area with early heat.
Plant Cool-Season Crops Early
The earlier you plant cool-weather crops, the more time they have to grow before hot weather arrives. If your soil is workable in early spring, get your seeds or transplants in the ground as soon as possible. If the area you live in has a tendency to get really warm in late spring, choose varieties that mature quicker. For example, I recently bought broccoli transplants and had a choice of two varieties at the garden center. One matured in 100 days, the other 70 days. I chose the one that matures in 70 days. That still has it maturing in May but hopefully before the 75-degree weather hits. If it does, I can try some of the tips below to keep them cool until time to harves.
Provide Shade for Sensitive Plants
If you garden in a warm climate, use a lightweight (30%) shade cloth to protect cool-season crops from excessive heat. You can also plant taller crops nearby to create natural shade.
Keep Plants Well-Watered
Drought stress can speed up bolting, so keeping the soil consistently moist helps slow the process. A layer of mulch can also help regulate soil temperature and retain moisture.
Succession Planting
Instead of planting everything at once, try planting small batches every couple of weeks. That way, if one group bolts, you’ll have younger plants still growing.
Harvest Regularly
For greens like lettuce and spinach, frequent harvesting encourages new growth and can delay bolting. Pick outer leaves early and often to keep the plant from maturing too quickly.
What to Do If Your Plants Bolt
Even with the best planning, some plants will bolt. When that happens, you have a few options:
- Harvest Immediately – Some vegetables, like lettuce and spinach, will still be edible if picked quickly, though they may taste slightly bitter.
- Let Them Flower – Many bolted plants attract pollinators and beneficial insects. Cilantro, dill, and radish flowers are especially good for this.
- Save the Seeds – If you’re growing heirloom or open-pollinated varieties, you can let a few plants go to seed and collect them for next season.
How Does Bolting Affect Flavor?
Unfortunately, bolting usually changes the taste of vegetables. Lettuce and spinach become bitter, radishes and turnips develop a woody texture, and herbs like basil may lose some of their best flavor. Cilantro and dill, however, can still be used even after they flower, though they may not be as tender.
Bolting is a normal part of a plant’s life cycle, but by planting at the right time, choosing heat-resistant varieties, and keeping plants cool and well-watered, you can delay it and enjoy your harvest longer. And when bolting does happen, consider leaving a few plants in the garden to support pollinators and beneficial insects. Every season I plant dill and cilantro in my garden and allow them to bolt. Ladybugs lay their eggs in dill and the parasitic wasp use the flowers for nectar.
Happy Gardening
Karen
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