This Common Garden Issue Will Make Your Herbs Taste Bad All Summer— What You Need to Do
On most plants, whether it’s ornamentals or edibles, the appearance of flowers is a reason to cheer. That is not the case, however, when certain herbs and vegetables send up flower stalks and go to seed. This process, called bolting,....

greatly affects their taste and makes your precious garden crops inedible.
Find out from an expert in the field why bolting happens in plants, what you can do to prevent it, and which types of herbs and vegetables may bolt.
Meet the Expert
Benjamin Phillips is a vegetable crops educator at Southwest Michigan Research and Extension Center of Michigan State University.
What Is Bolting?
Bolting is a reaction of cool-season crops to warmer temperatures and longer days, when a rapid shift in a plant’s hormones triggers flowering.
“These plants start to produce the hormones for flowering after their chilling threshold—a certain number of hours at cool temperatures—has been reached,” says Benjamin Phillips, vegetable crops educator at Michigan State University.
Bolting occurs once the period of cold exposure, called vernalization, is complete.
“Warm and hot days accelerate the plants’ flower development,” Phillips explains.
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Difference Between Bolting and Regular Blooming
“For vegetables that don’t produce harvestable fruit, bolting is usually undesirable,” says Phillips.
It is a premature flowering and seed production that cuts short the usability of the crops for consumption because the taste of the leaves turns bitter, and their growth is stunted. Regular blooming, on the other hand, is a desirable part of a plant’s lifecycle. Plants such as tomatoes produce flowers that are then pollinated and become fruit.
How to Keep a Plant From Bolting
To prevent plants from bolting, Phillips has a few suggestions. All of them require acting early, long before the plants are in your garden and about to bolt.
Store Seeds in the Freezer
The stage at which crops are receptive to cold exposure varies; for some of the crops, the receptiveness starts when they are seeds.
“The bottom threshold for accumulating chill hours is 32°F," says Phillips.
He recommends storing seeds like seed at below freezing temperatures.
“When you plant them, they will start accumulating vernalization points, but storing the seeds at freezing point will give you more time before the potential bolting process of the plants could start if the conditions are present," he says.
Don’t Plant Too Early
Seeding or transplanting too early in the spring can give plants enough time to reach their vernalization points. But the caveat is that they will then go straight to flowering instead of making lots of leaves or roots, Phillips explains.
Select Suitable Varieties
Choosing an appropriate variety for your planting season and location is equally important.
“Broccoli and cauliflower are flower buds, and we want these to go through a cold period,” Phillips says.
A variety adapted to your area or planting season will usually vernalize just fine, however, rare open-pollinated varieties from exotic places are less likely to succeed.
“You may find that a particular heirloom Romanesco cauliflower isn’t receptive to the temperatures in a typical spring in your area and will grow all summer into a massive pile of leaves without producing a head," Phillips says.
You can also look for varieties that are labeled as bolt-resistant such as 'Slo-Bolt' cilantro and 'Bloomsdale' spinach.
What to Do If Plants Already Bolted
If you have been unsuccessful in preventing or delaying the bolting, there are a few things you do.
At the first sign of bolting, if the plant is starting to shoot up but has not developed flower heads yet, harvest as many of the leaves as possible. If it is still early, the flavor might not yet be affected, and they might still be good to eat. Don’t wait, as the quality declines quickly, and a day or two can make all the difference.
If the plant is an open-pollinated heirloom variety, let the plant go to seed and collect the mature, dried seeds for your garden next year. This only makes sense for heirloom seeds, not for hybrid seeds (identified as F1 in seed catalogs), because these plants are created through controlled crossbreeding, and the seeds from those plants don't produce plants that are true to the parent.
Let the plant bloom—the nectar and pollen attract pollinators which improve the pollination of other garden crops such as summer squash that heavily rely on pollinators for a good crop.
As a last resort, pull the plant.
Plants You Should Always Keep From Bolting
This is a list of crops that can potentially bolt depending on when they were planted and how long they were exposed to their required cold temperatures. Spells of warm weather during the cold period and other factors also play a role in the likelihood of bolting.1
Not all crops on this list are equally prone to bolting. The most notorious crops to bolt include cilantro, lettuce, and spinach.
Cilantro
Lettuce
Radicchio
Beets
Swiss chard
Spinach
Basil
Bok choy
Broccoli
Brussels sprouts
Cabbage
Cauliflower
Collard greens
Kale
Kohlrabi
Mizuna greens
Radish
Rutabaga
Turnip
Carrots
Celery
Parsley
Parsnip
Members of the allium family (bulb-forming onions, shallots, leeks, garlic)
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