Why Is My Broccoli Bitter? (3 Ways to Avoid Bitter Broccoli)


Have you had it with bitter broccoli?  If so, you are probably wondering why it happens, and how you can avoid it.

So, why is your broccoli so bitter?  Broccoli becomes bitter when the plant starts to “bolt”, or produce flowers.  Broccoli will bolt due to age or environmental conditions.  Certain varieties of broccoli are also more bitter than others.

Of course, there are lots of different environmental conditions that cause broccoli to bolt and become bitter.

In this article, we’ll look at some of those causes and how to prevent bitter broccoli.

Let’s get going.

Why is My Broccoli Bitter?

Broccoli develops a bitter flavor when the plant starts to produce flowers, also called bolting.  It is a natural part of a broccoli plant’s reproductive cycle.

Often, broccoli will begin to bolt and produce flowers when the soil temperature reaches 80 degrees Fahrenheit (27 degrees Celsius).  Sometimes, bolting can happen before the broccoli forms a full-sized head.

Why is My Broccoli Bolting?

Broccoli bolts in order to produce flowers and seeds to create the next generation of plants.  Bolting can happen for several reasons, including:

  • Age (the plant has grown to mature size and is ready to reproduce)
  • Heat (the plant will flower early if it gets too hot)
  • Water Stress (under watering, especially during dry times)
  • Poor Nutrition (for example, low nitrogen levels)
  • Late Transplant (the plant was left indoors too long when grown from seed)

You can learn more about why broccoli bolts in my article here.

Let’s take a closer look at the reasons why broccoli bolts, starting with age.

Age

One simple but overlooked reason for bitter broccoli is age.  When a broccoli plant reaches a certain age, it is mature and ready to reproduce.

At that point, it will produce flowers and seeds in an attempt to reproduce.  Usually, this occurs after:

  • 65 to 90 days if you grow broccoli from seed (direct sowing in the garden)
  • 50 to 75 days if you transplant seedlings (starting seeds indoors)

You can learn more about when plants produce broccoli heads in my article here.

When broccoli plants are mature, the central head will be up to 8 inches (20 centimeters) in diameter.  However, most mature heads are 4 to 6 inches (10 to 15 centimeters) in diameter.

broccoli head
A mature broccoli head will be 4 to 8 inches in diameter. If you wait to long to harvest, broccoli will bolt and the head will taste bitter.

When your head of broccoli gets close to this size, it is time to start thinking about harvest.  It is best to harvest broccoli when the little green buds (florets) on the heads are still packed close together.

According to the University of Minnesota Extension:

“Harvest broccoli when heads reach a usable size, while they are still tight and before flower buds have opened.”

https://extension.umn.edu/vegetables/growing-broccoli#harvest-451964

The color of the head should be deep green.  If the heads are not tight and have begun to spread out or turn yellow, then the broccoli is bolting, and it will become bitter.

In a hot climate, you may have trouble getting broccoli to mature fully before the heat causes it to bolt.  In that case, you might consider some faster-maturing broccoli varieties, such as:

You could also opt for heat-tolerant broccoli varieties, such as:

Of course, if you want to grow broccoli without worrying about bolting and bitterness, then avoiding heat as they grow is the best way to do it.

Heat

Broccoli is a member of the brassica family (cruciferous vegetables).  The brassica family also includes cabbage and cauliflower.

Broccoli and other brassicas are cool weather crops.  Broccoli prefers to grow in cool soil, and can germinate in soil as cold as 40 degrees Fahrenheit (4 degrees Celsius).

The Old Farmer’s Almanac suggests starting broccoli seeds indoors 6 to 8 weeks before the last spring frost date.  Then, transplant them outside 2 weeks before the last spring frost date.

If you plant seeds directly outside, you can do so 2 weeks before the last spring frost date.  You can find frost dates for your area using this tool from the Old Farmer’s Almanac.

In general, you should not plant broccoli if temperatures are over 90 degrees Fahrenheit (32 degrees Celsius).  In fact, according to Texas A&M University:

 “High temperatures at heading time usually causes premature flowering and consequently reduces the quantity of home-grown broccoli. Broccoli will flower quickly if it is forced to mature at temperatures much above 80 degrees F.”

https://aggie-horticulture.tamu.edu/archives/parsons/vegetables/broccoli.html

When soil and air temperatures get too hot, broccoli will start to bolt and flower prematurely.  This will cause a bitter flavor in the heads.

Even if the heads are small, you should harvest them if they show signs of early bolting.  That way, you still get something from the plant.

broccoli plant
Harvest broccoli heads early if they start to bolt in the heat. That way, you can will get smaller heads, but they will not be so bitter.

Also, for varieties with a main head, you might still be able to harvest side shoots (ideal for stir-fries!) if the weather cools down a bit.

Water Stress

A lack of water during drought conditions will also lead to early flowering and bitterness in broccoli.  High temperatures, strong sunlight, and dry air can all contribute to this problem.

When broccoli does not get enough water, it may flower early.  This is because it wants to try to reproduce before it gets to the point where it cannot survive.

To avoid water stress, check your broccoli plants daily and water if the soil feels dry at a depth of 2 inches (5 centimeters) or deeper.

watering can
Water your broccoli plants to prevent water stress and prevent a bitter flavor.

If you have sandy soil, you can add compost or manure to make it retain more water for a longer time.  The extra organic material will also attract earthworms and beneficial bacteria to your garden.

A layer of mulch over your soil will also prevent evaporation due to heat and sunlight.  You can learn more about how to treat dry soil in my article here.

Poor Nutrition

A broccoli plant that is subjected to poor nutrition will also experience stress.  This stress will make the head taste bitter.

According to the University of Missouri Extension:

“Other causes of early flowering include nitrogen stress (too little).”

https://extension2.missouri.edu/g6400

You can often cure a lack of nitrogen in soil by adding some aged manure or a high-nitrogen fertilizer.

manure
Manure can add nitrogen to soil to help broccoli grow. Just be sure to use aged manure, not fresh manure, or you will burn your plants!

However, remember that a nutrient deficiency in plants may not always be caused by a lack of nutrients in the soil.  A soil pH imbalance or a lack of water can also lead to nutrient deficiencies in plants.

According to this chart from Research Gate, nitrogen and other nutrients will become less available to plants in soil that is too acidic.

Broccoli prefers soil with a pH in the range of 6.0 to 6.8 (slightly acidic).  If your soil is too acidic, you can add lime (calcium carbonate) to increase the pH.

Just be sure to do a soil test before adding anything to your soil.  That way, you can make sure that the pH is really off before trying to solve a problem you might not even have!

Late Transplant

It is probably best to transplant broccoli into the garden, rather than direct sowing.  However, you don’t want to wait too long to transplant!

https://extension2.missouri.edu/g6400According to the University of Missouri Extension:

“Broccoli that is planted too late in the spring will experience heat stress and flower early. Transplanting an oversized transplant will often result in premature flowering.”

https://extension2.missouri.edu/g6400

So, be sure to keep track of the age of your broccoli plant, based on when you planted the seed.  Remember to transplant broccoli outdoors at the right time (about 2 weeks before the last frost date).

How Do You Get the Bitterness Out of Broccoli?

If you have bitter broccoli that has already been harvested, the remedies above won’t help you.  So, how do you get the bitterness out of broccoli that has already been harvested?

Well, one thing you can do is to cook and season it properly.

When cooking bitter broccoli, try boiling rather than steaming.  When you boil broccoli, the water you drain out will remove some of the bitter compounds (baking or steaming will not do this).

After cooking, season the broccoli with flavors such as salt, spices, or citrus (lemon, orange, or lime.).

lemon tree
Adds some lemon juice to a stir-fry to help complement and offset the flavor of bitter broccoli.

Another option is to cut up the broccoli and use it as part of a stir-fry.  If you put it in a stir-fry with pineapple chunks, the sweetness of the pineapple juice will offset the bitterness in the broccoli.

Finally, remember that some people’s taste buds are more sensitive than others.  There is nothing you can really do about this, so if you taste bitterness in broccoli more than other people, chalk it up to genetics.

Conclusion

Now you know why your broccoli tastes bitter.  You also know how you can prevent it from happening in the future so that you can enjoy your harvest.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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