Broccoli is a delicious, nutrient-dense addition to the home garden. But when you go out to harvest some fresh broccoli, you find it covered in flowers where the familiar green crowns should be. What’s going on?
Broccoli flowers are a normal part of the plant’s life cycle, with the flowers producing seeds for the next generation. Flowering occurs once the broccoli head has passed the optimal harvesting stage, and they appear as a tight cluster of blooms on the plant. Broccoli bolting is a different kind of flowering, usually brought on by a stressful event that triggers the plant to produce emergency seeds. Bolted flowers appear on long stalks shooting up from the center of the plant.
In this article, you’ll learn more details about why broccoli flowers in the first place and the two different ways the plant produces blossoms. You’ll also learn how to slow the process so you can enjoy your broccoli harvest, and discover a few instances where flowers can serve a good purpose.
Let’s get started!
What is Broccoli Flowering?
Broccoli is a cool-season cruciferous vegetable that usually grows best in spring and autumn, although certain varieties have some degree of heat tolerance. Those distinctive green crowns we all recognize as broccoli are actually clusters of tightly-closed flower buds, and the heads are typically harvested before the buds open.
But if allowed to, your broccoli will morph into something of a bouquet of vibrant yellow flowers or a clump of tall flower stalks. These are two different things, with the first one being normal broccoli flowering and the second being bolting.
Normal Flowering vs Bolting
Even though both types of blossoms are small and yellow, the different types of flowering occur for different reasons.
Normal flowering. Like many plants, broccoli produces flowers that contain seeds to reproduce itself in the next generation.
“Normal flowering is a natural part of the plant’s lifecycle,” says Angelia Daugirda, Senior Manager of Creative Operations and copywriter for Organic Plant Magic. “At some point, the plant comes to full maturity after producing an abundant amount of food, and its efforts go towards producing seed and keeping its genetics alive and thriving.”
So flowering is an expected part of broccoli’s growth pattern- we just interrupt it by cutting off the crowns before the buds have a chance to open.
When broccoli heads are left in place to bloom, the flowers will remain compacted in a large cluster of yellow flowers. This is what normal flowers on broccoli look like:
Bolting. Bolting is when the broccoli plant shoots up a tall flower stalk and flower buds appear all over the stems.
The University of Minnesota Extension refers to bolting as premature flowering during the growth/development stage, usually due to some type of stress. Bolting occurs when the plant senses danger to itself, and it sends out emergency flowers to expedite seed production. This short-circuits your harvest plans, and it’s a disappointing thing for any gardener to see (I’m speaking from experience here!).
When broccoli has bolted, the yellow flowers occur on very tall stalks. This is what broccoli bolting looks like:
Can You Eat Broccoli That Has Flowered or Bolted?
If your broccoli has gone to flower or bolted, it’s technically still edible, but it will probably have an unappetizing, bitter taste. This is because the plant has diverted all sugar production to the flowers and seeds instead of channeling it into the crown buds, stem and leaves.
However, if you harvest the heads just after they’ve started to flower, the bitterness will probably still be fairly mild. And some people eat the actual flowers on broccoli- in fact, they’re considered a delicacy to certain people. Add broccoli flowers to salads, soup or as a garnish on any main dish. Just don’t steam your broccoli flowers- that can ruin their delicate texture.
Early Signs of Broccoli Bolting
There are some early signs of broccoli bolting, and if you’re aware of them and catch them early, you may be able to prevent your plant from going to seed.
Be on the lookout for scraggly-looking stems starting to shoot up or the heads staying small. These are signs of stress and impending bolting, so check soil temperature, moisture, sun exposure, and harvest those broccoli heads before your broccoli has flowered.
Will Broccoli Still Grow After Flowering?
There may be some leaf growth and more flowers, but your broccoli will no longer produce after bolting or flowering. You may see some side shoots growing, or smaller broccoli heads, which can be harvested but will never get as big as the initial crowns the plant produced.
Causes for Broccoli Plant Flowering
So we’ve established that broccoli flowering and bolting will end production.
The best way to avoid your broccoli going to its normal flower stage is to harvest the crowns while they’re still in bud form. And that’s pretty easy- you’ll just have to check on your plants more often and bring your harvesting knife/shears along!
On the other hand, bolting can happen before your plants reach the optimal harvesting stage, so the more pressing question is what’s causing your broccoli to bolt? The short answer is stress, but that can take a few different forms:
- Hot soil
- Cold soil
- Root constriction
- Lack of moisture
- Long hours of sunlight
- Too much fertilizer
Let’s take a look at all of the possible causes for bolting broccoli.
1. Hot Soil
It’s not so much the air temperature or hot weather, but hot soil that can lead to your broccoli bolting. Broccoli plants grow best in cold weather, or in soil that is between 65 and 75 degrees Fahrenheit. If temps are higher than that, your broccoli plant will sense danger and bolt.
2. Cold Soil
The flip side of overly warm soil is soil that’s too cold. Soil temperatures that consistently stay below 50 degrees F can also lead to broccoli bolting. This could happen if an early winter hits a fall broccoli crop, or if a late cold snap occurs in the spring.
3. Root Constriction
Roots are the lifeline for plant growth and sustenance, so when they’re constricted or damaged it can cause your broccoli to panic.
Till up soil and remove rocks or solidified clay, then add compost to enrich the soil before planting your broccoli seedlings or plants. Be sure to leave plenty of space between plants- overcrowding the garden can impede root growth. About 18 inches between broccoli plants should be enough space.
Also, be aware that if you’re transplanting broccoli plants from indoors to outdoors, a late transplant can also lead to broccoli bolting. The roots could already be tightly packed in the seedling pot, and the transplant may be too great of a shock for the plant.
4. Lack of Moisture
If there’s not enough moisture in the soil, your broccoli could sense impending death and bolt while it has the chance.
A lack of moisture can be due to dry regional conditions, sparse rainfall and not watering enough each time you water. Broccoli needs at least 1 inch per week of rain or watering to grow and develop into usable heads.
5. Long Hours of Sunlight
As days grow longer and more sunlight is hitting your broccoli plants, your plant can sense that it needs to rush to end the growing season by producing seeds.
6. Too Much Fertilizer
Applying too much fertilizer to broccoli plants can create excess heat in the soil as the ingredients decompose. Even though broccoli requires a great deal of feeding, improper fertilizing of broccoli will have some negative effects from bolting to plant death.
How to Keep Broccoli From Bolting
To keep broccoli from bolting, the best thing you can do is provide the proper care and optimal environment. There are some things you have no control over, like days getting longer in the summer, but there are several ways to suppress or slow your broccoli’s bolting instinct:
- Plenty of water
- Harvesting early in the season
- Providing shade
- Direct sowing or transplanting early in the season
- Appropriate fertilizing
- Planting bolt-resistant varieties
Mulch is the number one way to keep the soil cool, which helps the broccoli plant’s root system cool as well. Lay mulch on pretty thick, at least 1-2 inches, around the base of each broccoli plant.
Some good mulch materials include:
- Grass clippings (as long as they’re not treated with any lawn-care chemicals)
- Shredded leaves
- Cocoa bean hulls
2. Plenty of Water
Broccoli loves good moist soil. If you live in a dry area or there’s no rain in the forecast, be sure to give your broccoli plants about 1 inch of water weekly. Make sure the soil is soaked thoroughly, at least 6 inches deep. You can also test soil moisture with a soil moisture meter.
3. Harvesting Early in the Season
Harvest broccoli crowns when their buds are still tight and the heads are between 4-6 inches in diameter. Harvesting signals to the plant to stay in growth and production mode instead of veering into end-of-season.
When cutting the initial broccoli crown off the plant, leave a section of the stalk behind. You’ll see some side shoots or smaller broccoli heads that will grow that can also be harvested once they reach a good size.
4. Provide Shade
When there’s lots of sun shining brightly and you want to prevent bolting broccoli, consider some row covers. Some lightweight fabric or garden netting can do wonders to protect your broccoli plants from sun, heat and insects.
5. Direct Sowing/Transplanting Early in the Season
When planning your broccoli planting times, your regional projected frost dates are a key piece of information. You can find your local dates on the USDA frost zone map.
In the spring, don’t wait too long before getting your broccoli into the garden- take full advantage of those cool early-spring days! You can direct sow broccoli seeds in the garden roughly 2 weeks before your last expected frost date, but starting them indoors gives you a head start for the growing season.
Daniel Akins, writer and editor at Theyardable, agrees. “The ideal place to start broccoli seeds is in a greenhouse. Six to eight weeks before the latest frost date, you can put the seeds in seed flats. When the last frost has passed and the outside temperature is around 50 degrees, you can plant the broccoli outside once it is a few inches tall and has some growth on each stem.”
Broccoli also makes a great fall crop. Since you’ll be planting seeds in mid to late summer, starting them indoors is the best way to protect the vulnerable seedlings from the heat. Plant your seeds about 11 weeks before your first projected frost date, and transplant outdoors about 6 weeks after that.
6. Appropriate Fertilizing
Broccoli needs just the right amount of fertilizer at just the right times for optimal growth and production. Use a balanced fertilizer, like Dr. Earth Home Grown, about 3 weeks after seedlings have been transplanted, and again just after the broccoli heads reach about 1 inch in diameter.
Be sure to follow the manufacturer’s recommendations for dilution and use, and always give plenty of water whenever you apply fertilizer.
7. Plant Bolt-Resistant Varieties
Another way to prevent flowers on broccoli is to plant varieties that have a natural resistance to stress factors. These include:
- Di Cicco
These bolt-resistant varieties are known to be heat-tolerant, with most reaching maturity in 60 to 65 days.
What Should You Do After Broccoli Flowers?
After your broccoli flowers or bolts, there are a few things you can do to maximize the plants in your garden.
Let’s take a look at some suggestions for your flowers on broccoli.
Save the Seeds for Next Year
When you leave broccoli flowers in place, pollination can occur and seeds can form. This is a great way to collect seeds for next year’s garden, as long as your plants meet a couple of criteria.
Firstly, be sure that your broccoli isn’t too close to any other members of the brassica family since these plant relatives easily cross-pollinate. If you have your broccoli within about 300 feet of cauliflower, kale, cabbage, bok choy, mustard or Brussels sprouts, you may end up with a strange, inedible broccoli hybrid next year.
Also, if you planted a hybrid variety of broccoli, the plant probably won’t produce seeds that are true to type. Hybrids are man-made crosses between plants, and the traits of either of the parent varieties may show up in the seeds saved. Heirloom varieties are your very best bet for saving seeds that reliably reproduce themselves each generation.
Saving seeds from broccoli isn’t quite as straight-forward as some other seeds, but it’s still a fairly simple process:
- After pollination, the flower petals drop leaving behind wispy tendrils that will plump over several weeks. When the plant turns brown and the seed pods have plumped, snip the stalks off with your garden shears.
- After the pods have dried, break them off and collect the seeds by rolling the pods between your fingers or putting them in a bag and shaking them.
- Allow seeds to fully dry in a bag or tray for several days, then store in a paper bag in a cool and dry spot.
This video from How To… Garden, Garage and Home does a nice job of demonstrating the seed and harvesting process:
Broccoli seeds can remain viable for up to 5 years after collection, but you’ll usually have the best results planting the year after harvesting the seeds.
Allow the Flowers to Attract Pollinators
The bright-yellow flowers on broccoli are great for attracting beneficial insects and pollinators like bees and butterflies to your garden. Friendly insects are essential for pollinating other plants and flowers, which means you’ll have more veggies and flowers soon. So let those broccoli flowers bloom and reap the benefits!
Enjoy the Color in the Garden
Broccoli flowers have a pretty and quite striking yellow color in the vegetable garden. It’s a nice contrast to all of the green and any other plants you’ve got growing in your gardens. So enjoy it while it lasts!
Frequently Asked Questions about Broccoli Flowers
Finding your broccoli bolted or full of flowers can be a surprise to come across in your vegetable garden. While you can’t always prevent flowering and bolting, a few maintenance steps from proper watering, monitoring soil temperature, and timely harvesting can help a lot.
We want to hear from you! Are there any tips you’d like to share for a bumper broccoli crop? Or maybe you still have some more questions about flowering and bolting. If you’re wondering about it, someone else probably is too- so please share your thoughts in the comments!