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Why Is My Broccoli Flowering – Causes & Fixes

Broccoli isn’t considered a beginner’s gardening plant. It can be fickle, has a pretty short time slot to grow in, and fairs better in cooler weather. Something probably most gardeners have dealt with if they’ve grown broccoli is broccoli that begins flowering or “bolting.” Sometimes this will even happen before the heads of broccoli grow. Flowering or bolting is a survival mode for the broccoli plant. The point is to start producing seeds before they die to prepare for the next generation. 

When a broccoli plant begins to flower, something stresses the plant out. Most often, the weather is the cause. Broccoli will begin to flower if it becomes too hot or too cold. There are other things to think about, like transplant shock or lack of nutrients. Luckily there are ways we can prevent this; however, once a broccoli plant starts to flower, there is no stopping it.

To find out more about why broccoli starts bolting and how to prevent this, continue reading. 

Reasons Broccoli Begins to Flower

Stress to any plant will cause the plant to do strange things; in this case, when broccoli is stressed out, it may begin to flower or start “bolting.” Let’s look at all the reasons why broccoli starts to flower.

Too Hot

Heat is usually the answer to why your broccoli is bolting. Broccoli grows best when the soil temperature is about 65-75 degrees. Anything above 75 and the plant will start to shut down and flower, signifying the end of its life. Heat is usually the issue because, most times, gardeners will plant their broccoli as an early spring crop and leave it in the ground until the heat comes around and it starts to bolt. 

Too Cold

Opposite from heat, broccoli can also start to bolt if the weather gets too cold. Usually, broccoli can withstand temperatures around 50 for a while and do pretty well. Anything below that, however, and the plant may begin to die. Broccoli is also very frost-sensitive.

Lack of Nutrients

If a plant, such as broccoli isn’t getting the nutrients or energy they need to continue growing; it will shut down. In broccolis case, the start of the shutdown is to start flowering. 

Root Damage

Whether you decided to transplant your broccoli plant, or maybe an animal messed with the roots, any root damage could signal the plant that it is in danger and it is time to end its life.

How To Prevent A Broccoli Plant From Flowering

As I mentioned earlier, it is possible to prevent broccoli from flowering; however, there is no going back once broccoli starts to flower; here are some preventative measures you can take.

Weather

Since broccoli has such a short window of time that it can grow, you have to be pretty on point when you sow your seeds. Broccoli seeds are best planted in a greenhouse. You can plant the seeds in seed flats 6-8 weeks before the last frost.

Once the broccoli is a few inches tall with some growth on each stem, you can plant it outside once the frost is over and the outside temperature is around 50 degrees. The broccoli should continue growing happily up until the weather starts getting hot, or early-mid summer, depending on your location.

On the flip side, you can also grow broccoli as a fall crop. Sow your seeds in seed flats in late summer, about six weeks before the weather starts cooling down, and plant them outside when they are ready. This may be a little trickier since you don’t want the frost to come early and kill your plants. 

Heat Protection 

The weather has a mind of its own, and sometimes it may come before your broccoli is ready. There are measures you can take to try and protect your broccoli from the heat. Adding a layer of organic, excellent quality mulch over the top of your soil around the broccoli will protect the roots from getting burned and will prevent the soil from getting too hot.

This will also trap any moisture. You can also use a layer of straw. Mulch is the best heat protection, though you can also set up shade cloth around your broccoli plants to keep them from getting too blasted by the hot summer sun. 

Nutrients

To avoid a nutrient issue, you can do a couple of things. First, before you even plant your broccoli outside, make sure you have well-fertilized soil. Broccoli likes a high nitrogen diet, so having a fertilizer with high nitrogen already in your soil before planting makes a big difference. Broccoli needs a lot of nutrients and is considered to be a heavy feeder.

Usually, fertilizer alone won’t hold up for the whole time you have broccoli in the ground. It is recommended to use a liquid feed once a week on your broccoli plants to ensure they are getting enough nutrients. Nitrogen liquid feeds are sold at garden stores. You can also apply alfalfa meal, compost, or chicken manure every few weeks to help out with the feed. 

Are Broccoli Flowers Edible?

This is also a question people ask if they are wondering if they can even remove broccoli flowers. There is no harm in removing the flowers since the plant has reached the end of its life anyway. Removing the flowers will not reverse the bolting from happening.

A wonderful thing about broccoli is that practically the whole plant is edible. Even the leaves, stems, and flowers make for great additions to salads and stirfry. If your broccoli has bolted, don’t let it go to waste! Harvest the leaves and the flowers and try making a broccoli salad or saute everything with garlic and lemon. 

A word of caution, some find the flowers of broccoli to be very bitter! Some people love it; some people do not care for it. But instead of wasting them, use the stir fry route instead of a salad so you can use many spices and other flavors to balance out the bitterness of the broccoli flowers. 

When To Harvest Broccoli

Broccoli will only have one main head in the center of the plant. However, once that head is harvested, the plant will throw off new shoots if the conditions are right. It is good to harvest that main head as soon as possible, once it looks big enough to harvest. If the plant starts to flower, you at least harvested the main head. The main head is much more likely to flower than the offshoots. 

What Other Vegetables Bolt Like Broccoli?

Broccoli isn’t the only vegetable known for bolting. Other vegetables will do this as well for the same reason as broccoli, for survival. Some (not all) other vegetables go through a flowering stage. 

  • Cilantro
  • Spinach
  • Basil
  • Lettuce
  • Onions
  • Leeks

Does All Broccoli Bolt?

Scientists have created genetically modified varieties of broccoli that are tolerant to bolting. Of course, the plant will still flower at some point because that is its natural cycle; however, the plant may be able to take a lot more heat/cold, and it will take a lot longer to bolt. These are some varieties that are bolt tolerant. 

Athlete – known for being able to grow in high and low temperatures, a slow bolter

Destiny – known for being a mid-summer variety of broccoli, incredibly heat tolerant 

Spring Raab – a version of baby broccoli or broccolini, can be harvested well into summer and is a slow bolter.

Sun King – this beautiful blue and green-tinted broccoli is known for being an extremely hardy variety, very tolerant of sun and colder temperatures, and is one of the top producers in the broccoli world 

How to Grow Broccoli (from seed)

As I mentioned earlier, broccoli isn’t a beginner vegetable. However, that doesn’t mean you shouldn’t try it if you are a beginner. I personally always start my broccoli from seed. Here is a complete guide to growing broccoli. 

Sowing Seeds

Broccoli can grow wonderfully from either being directly seeded (put right into the ground) or planted first in seed trays. I usually start my broccoli in seed trays because it is a cooler climate vegetable; it’s easier for the seeds to germinate with regulated heat. Broccoli should be planted indoors 7 to 9 weeks before the last frost.

Once the seeds are sowed into seed trays about 1/4 deep into organic, fertilized potting soil, then they can be placed somewhere warm with a plastic cover over the top. I like to keep my seed trays moist almost all of the time and make sure they stay warm. Once they germinate, they should be under lights or sun for about 8-10 hours a day. 

Planting Seedlings 

Generally, once the seedlings are about 5 inches tall and have many leaves, they are ready to be planted. The weather outdoors should also be around 70 degrees consistently. When you plant outdoors, make sure your soil is well-draining and rich in nutrients. Broccoli likes partial shade, especially shade during the hotter times of the day. 

Caring For Plants

At this point, your broccoli should be thriving. Broccoli needs about one inch of water a week, slightly more if the weather is hotter. If the leaves look a little yellow or the plant isn’t growing the way it’s supposed to, doing a liquid feed is always helpful. Since broccoli is a heavy nitrogen feeder, using a nitrogen liquid feed once a week if needed will keep the plant happy and looking healthy. 

Harvesting

All together, broccoli takes 80-100 days from seed to harvest. However, it should be about 55-70 days once transplanted outdoors until you see the main head ready to harvest. The main head always grows first, right in the center of the plant.

You’ll know it’s ready for harvest when it’s about 4-8 inches across and has that nice deep green, almost purple-looking broccoli color. If it begins to turn yellow (which it will do quickly if it’s not harvested on time), you’ve waited too long.

Once the main head has been harvested, more than likely, offshoots will grow and produce smaller heads of broccoli. With certain varieties and if the weather is changing, this doesn’t always happen. Most gardeners will leave the broccoli plants up until they start to flower. 

Why is My Broccoli Plant Flowering But There Are No Heads?

If your plant has started to flower, but it never produced any heads of broccoli, this likely means the plant didn’t have the right conditions for broccoli to head A lack of nutrients would most likely be the answer, or the weather started turning. Broccoli will also flower after a particular time has gone by anyway. So if you waited too long to transplant, and the plant is still small after so many days, it will begin to flower. 

Final Thoughts

Broccoli is a very fun vegetable to grow, and you can get a few heads out of one plant if you are lucky and if the conditions are right. No matter what, broccoli will begin to flower as that is the natural cycle of a broccoli plant.

Flowering or bolting means the plant’s life is coming to an end, and it’s trying to send out its pollen and seeds to get ready for the next round of plants. This usually happens because the weather has gotten too hot, but maybe the weather is too cold, or the plant doesn’t have the nutrients to keep going.

Don’t let anything go to waste, though; you can eat practically the whole plant, and the flowers make sure delicious salads and stir-fries! Happy gardening!