Is Your Broccoli Bolting Here’s How To Prevent Broccoli Flowers From Appearing Prematurely

Have you gone into your garden on a hot summer’s day and found your once-perfect broccoli has suddenly shot up scraggly stems that have started to flower?

If so, then your broccoli has bolted, where they start growing tall and flowering can occur early on instead of growing larger heads first.

Bolting or going to seed is a plant’s response to stress, and most plants bolt when the hot weather hits, the hours of daylight lengthen and the ground temperature reaches a certain temperature.

There are several stressors that cause broccoli to bolt or start to flower, but the number one cause is heat. Other causes can be excessive sunlight or other stress on the roots. 

So is there a way to keep broccoli from bolting? Let’s explore this in detail and go over cause broccoli plants to bolt, how to delaying broccoli flowers from appearing prematurely, and whether your broccoli is safe to eat after the buds open into tiny yellow flowers.

What Does It Mean When Broccoli “Bolts”?

What Does It Mean When Broccoli “Bolts”?

As broccoli matures, it will flower and produce seed. This is part of the natural cycle of the plant. This should not be confused with bolting, which is the plant’s response to unfavorable growing conditions. 

Broccoli will bolt when the plant’s roots become stressed and it goes into emergency response mode to produce seeds for self-preservation.

Signs To Watch For That Your Broccoli Is Starting To Bolt

Signs To Watch For That Your Broccoli Is Starting To Bolt

There are several different indicators that your broccoli has, or is going to, bolt. Here are the main signs of bolt:

  • Flowering Stems: Most likely, bolting broccoli will send up a tall stem that will begin to flower. This stem will grow very quickly and can become quite tall. 
  • Flowering Heads: If your broccoli heads are already quite large when the plant starts to bolt, the heads themselves will often burst forth in bright yellow blooms. 
  • Stunted Heads: Alternatively, the heads will sometimes remain stunted and small when the plant begins to bolt.

Can You Still Eat Broccoli When It Starts To Flower?

Can You Still Eat Broccoli When It Starts To Flower?

Basically, bolting broccoli is not fit to eat. While it is still edible (as are the flowers), the leaves and florets will usually become bitter. The stalks and stems, which are usually so juicy and delicious, will become tough and woody.

But don’t give up all hope. If you catch your bolting vegetables early enough, the broccoli heads might still be good to eat.

They probably won’t be as tasty or nutritious, but if your harvest as soon as signs of bolt are observed, you can probably get a few decent meals out of it.

Can you save a bolted broccoli?

Yellow broccoli flower in the vegetable garden

So, is your bolted broccoli good for nothing? On the contrary, bolted broccoli can still benefit your garden by adding beautiful yellow flowers to an otherwise sea of green.

Pollinators, such as bees, butterflies, and hummingbirds will be drawn by the blossoms, and you might be lucky enough to be able to save your own seeds for next year’s garden (but make sure your variety is not a hybrid first). 

When your broccoli starts to bolt, the actual cell structure of the plant changes. Attempting to remove the bolting stems or flowers will simply cause more to take its place. Unfortunately, once the process has started, you cannot stop your broccoli from bolting.

The best solution is prevention.

Will broccoli grow after bolting?

Will broccoli grow after bolting?

Once your broccoli has bolted, the main head will generally stop growing as all the plants energy is now going into flower and seed production.

However, once you cut the main head (whether it is still edible or not), the plant will start producing side shoots and small florets which will keep growing.

What Causes Broccoli To Bolt?

What Causes Broccoli To Bolt

There are a few things that cause broccoli to bolt. It is important to know the reasons so you can best prevent broccoli from bolting before they are ready to be harvested.

  • Heat: The most common cause of bolting broccoli is heat. Broccoli is a cool-season plant and does best with a soil temperature between 18°C and 24°C (65°F to 75°F). As the summer temperature starts to rise above this, the broccoli roots overheat and focus on self-preservation. 
  • Sunlight: As the days lengthen and the rays of the sun intensify, the cool season plant again starts to produce seed to battle the summer weather. 
  • Root Stress: Other stresses on the root, such as becoming rootbound or being damaged, can also cause broccoli to bolt, or go to flower..

How To Keep Broccoli From Bolting

How To Keep Broccoli From Bolting

Here are some tried and true measures you can take that will protect your broccoli from heat and other stressors to keep your carefully cultivated plants from bolting:

  • Mulch: The best way to keep your broccoli from bolting is to protect the roots from getting too hot. Apply a thick layer of organic mulch, such as straw, around your broccoli to insulate the ground, trap in moisture, and shield the soil from direct sunlight. Putting cardboard under the straw will also really help with weed suppression. 
  • Create Shade: Since sunlight is a big trigger that causes bolting, shading your broccoli from the sun can help a lot. There are many different ways you can provide shade. You can use row covers, put up shade cloth, use a patio umbrella, or surround your broccoli with tall, fast-growing plants. 
  • Succession Sowing: Planting a few broccoli every week or so instead of all at once will mean that your plants will be at different stages if the weather suddenly turns hot. That way, they all won’t react the same to the heat and some stages of growth will be less likely to bolt. 
  • Keep Your Soil Healthy: Planting your broccoli in good, healthy soil will help it grow quickly so it will be ready before the heat comes.
  • Transplant Early: If you start your broccoli indoors, make sure you transplant them before they become root-bound in their pots. If the weather is still too volatile for the delicate seedlings, move them into larger pots until they are ready for transplanting. 
  • Harvest Early And Often: Remember that broccoli will grow new side shoots after you harvest the main head. These side shoots are less likely to bolt than the main head. As a hot summer approaches, consider harvesting early, smaller heads before they bolt and you can still count on harvesting the regrowth.
  • Bolt-Resistant Varieties: Some varieties of broccoli are bred to be more resistant to bolt. If you feel your broccoli might not be ready before the summer heat, consider growing a bolt-resistant variety.


It is always sad to see your beautiful vegetable garden turning inedible before your eyes. Hopefully,

you will now be able to notice the signs that your broccoli is starting to bolt so you can harvest it and still eat your slightly-flowering head of broccoli.

Or better yet, you will be able to prevent your broccoli from bolting altogether and enjoy this cool-season vegetable at its peak.

Amber Noyes

Written By

Amber Noyes

Amber Noyes was born and raised in a suburban California town, San Mateo. She holds a master’s degree in horticulture from the University of California as well as a BS in Biology from the University of San Francisco. With experience working on an organic farm, water conservation research, farmers’ markets, and plant nursery, she understands what makes plants thrive and how we can better understand the connection between microclimate and plant health. When she’s not on the land, Amber loves informing people of new ideas/things related to gardening, especially organic gardening, houseplants, and growing plants in a small space.

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One Comment

  1. Avatar photo Helen Schultz says:

    Thank you very much for this article. I will try again, hopefully I have collected some usable seeds. I had NO big heads, or small ones! We used some florets in salads, but even those were not many. I planned on never planting broccoli again. Now I will sow earlier that our very hot summer days do not harm them. I will also put shade over them. Regards from South Africa