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Bolting Broccoli: What It Means & Tips To Delay Flowering

Despite its abundance of nutrients and ease of cultivation, many gardeners face a common obstacle while growing broccoli: bolting. This is a recurring concern among those cultivating this vegetable.

That’s when the broccoli heads start to flower, which means they’re no longer form tight heads and they will have a bitter taste.

Why is my broccoli plant flowering? Broccoli plants go into the flowering phase due to drastic changes in the growing conditions or the environment. If the soil temperature goes up or drops suddenly or if the plant is stressed due to poor irrigation, it will start flowering and begin to bolt, a process that cannot be stopped.

With proper care, you can prevent broccoli bolting and keep the heads of the veggie tight and edible until it’s time to harvest them.

Read more to understand the main reasons for bolting broccoli and what you can do about them.

Broccoli Bolting: What To Know

As a cool weather plant, broccoli is quite sensitive to high temperatures.

Much like garlic and onions, broccoli will go straight into the flowering phase if the soil temperature changes suddenly or if the plant is under stress for too long.

What Does Bolting Broccoli Look Like?

If you see yellow flowers on broccoli, that’s a sure sign the veggie is bolting. It’s usually the last thing you’d want to see on the heads of the broccoli unless you’re growing the veggie to harvest the seeds.

You can still eat broccoli heads with flowers on them, but they usually taste bitter and are chewier than young broccoli heads. 

You’ll also see a long stem growing out of the middle of the vegetable. At the top of the stem, small buds form that open into small yellow flowers.

The head stops growing and the plant devotes all its resources to developing the flowers.

Bolted broccoli with numerous yellow flowers.

What Causes Broccoli To Bolt?

Broccoli plants can bolt for many reasons. In a way, bolting is a survival mechanism kicked in by changing weather conditions or as a result of the plant being under stress. 

However, it’s important to make a distinction between hot weather and hot soil.

The weather can be hot, but as long as the soil is cool, broccoli will not bolt. This will come in handy when you try to prevent premature flowering.

Another reason for bolting broccoli is stress. If the plant is not getting enough water regularly, it will bolt. Watering also cools down the soil to keep the broccoli from flowering.

Can Bolting Be Stopped?

Once broccoli starts bolting, there’s no way you can reverse that process or stop it.

The veggie will continue to flower, and the stem will keep growing and taking up resources as the head itself becomes bitter and chewy.

However, you can prevent bolting before it happens by providing adequate growing conditions around the vegetable and preventing the soil from getting hot.

Can You Eat Bolted Broccoli?

Bolted broccoli is bitter and chewy. The plant directs all its resources into developing the long stem carrying the flowers.

If the head itself starts to flower, then you can’t eat it. However, if you harvest broccoli before the stem grows and the head is covered with flowers, you can cook it and eat it. 

What To Do When Broccoli Goes To Seed

When broccoli goes to seed, you have two options. The first is to let the plant flower and seed; then you can harvest the seeds to use next season.

You’ll have enough seeds for several broccoli patches for many years to come.

The other option is to harvest the heads as soon as you can and store them in the fridge. They might be too bitter to eat raw or in a salad, but when cooked, they will soften up.

You can also harvest the flowers and new shoots for cooking. They might not be as tasty as unbolted broccoli, but it’s better than letting the broccoli patch go to waste.

Broccoli Growth Stages

Broccoli growth goes through many stages. You need to know about these stages to determine the right time to harvest the heads before they start flowering.

Here are the main growth stages of broccoli:

  • Germination: The seeds of broccoli start to germinate between 7 and 10 days after planting them.
  • Sprouting: Once the roots develop and start absorbing nutrients and moisture from the soil, the first shoot breaks the surface of the soil.
  • First True Leaf: Once the first true leaf emerges, the plant’s growth accelerates. It can now use photosynthesis to produce its own food.
  • Third True Leaf: With the third true leaf set, the stem growth picks up pace, and the plant will start to take a miniature shape of the mature broccoli.
  • Main Head: The main head starts to develop, and that’s when you need to provide the plant with mulching and regular watering to cool down the soil. Other forms of vegetative growth in the plant come to a full stop. All resources go into developing the broccoli head.
  • Harvest: Once the head has developed fully with a compact shape and the buds are unopened, it’s time to harvest the broccoli. If you delay this process, the buds will open and the plant will go to seed.
  • Side Shoots: After harvesting the main head, the plant develops side shoots that will in time become small broccoli heads. Once they develop fully, you can harvest them.
  • Flowering and Seeds: Any unharvested heads will start to flower, and after pollination, seeds will form. When the seeds are fully developed, the plant will perish. You can harvest the seeds and use them the next season.

Chart showing broccoli growth stages

Signs That Broccoli Is Going To Bolt

Broccoli takes time to fully bolt. During the early stages of bolting, you can still harvest the head and wait for the small shoots to develop. You will also notice the following signs.

  • Flowering Head: When you see little yellow flowers sprouting on the heads of the vegetable, that means the plant is bolting.
  • Flowering Stem: When the plant senses the soil getting hot, it will send a tall stem up that blooms with yellow flowers. 
  • Small Head: Once the broccoli bolts, the head will stop growing and become stunted. All the plant’s resources will go into flowering from that point on.

Bolt-Resistant Broccoli

Some broccoli cultivars are more heat-resistant than others. Those cultivars will not bolt as fast as natural broccoli varieties even if the soil gets hot.

Here are some of these bolt-resistant broccoli varieties:

  • Belstar: This cultivar is grown mainly for its heat-resistant properties. The main head is about 6 inches wide and reaches maturity within 65 days.
  • Destiny: The heads are small and take up to 75 days to develop, but this cultivar grows well in Zones 7 to 11 and has good heat resistance.
  • Sun King: The heads of this cultivar can grow to 8 inches wide and will mature in 70 days. It’s resistant to both hot and cold climates and is hardy to Zones 1 to 11.

When To Plant Broccoli

In warm zones, the best time to plant broccoli is in late summer. That way the cool-season broccoli will have enough time to develop in cool weather.

If you plant broccoli in the spring, start it early so that it matures before the summer.

Tips To Delay Broccoli Bolting

The best way to prevent premature flowering in broccoli is to avoid the main causes of bolting: hot soil and stress. The following tips may come in handy:

  • Mulch: Cover the soil around the base of the plant with a thick layer of mulch to keep the soil cool.
  • Water: Water the plant regularly to cool down the soil and prevent stress.
  • Row Covers: If you plant your broccoli in rows, consider using cover rows to prevent the soil from becoming too hot.

Harvesting Broccoli

You can start harvesting broccoli as soon as the head reaches its full development. Harvest time varies depending on the cultivar, but it can start as early as 50 days from planting the seeds.

Once you harvest the head, the plant will send out side shoots that will develop into smaller heads. Those can be harvested as well.

Related Questions: 

Why Is My Broccoli Not Forming Heads?

This could be a result of overcrowding or because the root system is damaged.

If you transplant the seedling a bit late, that could impact the development of the rootball, which prevents the broccoli from forming heads.

Are Broccoli Leaves Edible?

Broccoli leaves are edible, but they’re bitter and chewy just like kale. However, you can prepare them like kale or Swiss chard.

Conclusion

When broccoli bolts, the head stops growing and turns slightly bitter and chewy. You can prevent the veggie from bolting with mulching, regular watering, and row covers.