Why Does Broccoli Grow Bitter?

Alright. I wanna know what’s up with my broccoli plants! Every head I harvest is bitter!

I had the same problem last year. I figured I’d just planted it too late last year, and that the heat had caused the trouble. So I got my broccoli in the ground several weeks earlier this year, but it still happened.

harvested broccoli in basket
harvested broccoli in basket

My neighbor grows the most beautiful heads of broccoli every year, and never has bitter broccoli. She even harvests side-shoots throughout the summer, so it can’t be the heat that is affecting them.

My broccoli looks a little yellowish to me, too. Does that mean it’s lacking something? I side-dressed it with plenty of straw and chicken manure.

I also thought I might not be picking it soon enough. If you leave broccoli florets too long, the buds will begin to open up. When this happens, it does get bitter. But I tried harvesting the small side-shoots as soon as they popped out, and they still tasted horrible.

What gives? Why is my broccoli growing bitter?

Broccoli usually turns out bitter due to stressors in its environment, such as too much sun, high temperatures, cold temperatures, a lack of water, or improper soil conditions. Managing these stressors and providing optimal conditions will reduce bitterness.

broccoli plant in the garden
broccoli plant in the garden

I considered that it might have been the variety I planted, but this year I used two different varieties (one heirloom, one generic pack of Green Sprouting Broccoli) and they were both bitter. Now that I think of it, the heirloom variety was also called Green Sprouting. Maybe that’s the problem?

Maybe my plants are in more direct sunshine than my neighbors. Maybe if I planted them in a semi-shaded place they might do better? I think I’ll replant in the Fall and see if I have better luck.

It stinks to have all of this broccoli and none of it is edible. But I found answers to this aggravating problem, and I will share them with you in the rest of this article.

What is the Science Behind Bitterness in Broccoli?

For many of us, the mention of broccoli brings to mind thoughts of childhood vegetable battles and tortured pleas of, “just one more bite.” But what exactly is it about this unassuming little green veggie that makes it so unpalatable to some?

The answer lies in a class of chemicals known as glucosinolates. Glucosinolates are sulfur-containing compounds that give broccoli (and other cruciferous vegetables like spinach, brussels sprouts, chard, cabbage, and kale) their characteristic bitterness. When the plant tissue is stressed or damaged, enzymes are released that break down the glucosinolate compounds into molecules called isothiocyanates.

These molecules interact with our taste receptors to create the perception of bitterness. Some people have a higher sensitivity to bitter tastes than others, which may help explain why some folks just can’t stomach broccoli while others love it. 

So, that explains what causes the broccoli to be bitter. Interesting stuff. But how do we stop that process from happening while it is growing? 

Reasons Why Your Broccoli is Turning Out Bitter

Harvesting broccoli again and again only to have it turn out  bitter and inedible can be quite disappointing. As I mentioned above, this can be a quite a mysterious issue, and one that seemingly persists no matter what solution you try. I got lots of advice in my quest to run down this problem and discovered that it all boils down to one thing: stress.

No, I don’t mean stress for me and other gardeners; II am talking about stress for the plant itself! When broccoli plants are stressed, in any way, they will get more and more bitter as a natural result. What counts as stress?

It could be anything that is “non-optimal” conditions: it could be too much or not enough light, the wrong soil conditions, too much or not enough moisture, you name it!

It is important to make sure your broccoli plants are growing in the best conditions possible to avoid this bitterness. This is also why it is so easy to “fix” something when growing broccoli only to have it turn out bitter anyway; you might eliminate one stressor, only to others remain.

When the broccoli is stressed, it will bolt a process in which it stops producing heads and instead begins to produce flowers.

This is another cause of bitterness, since the plant will then begin to produce those bitter compounds as a natural result. If your broccoli starts to bolt, it is best to harvest it quickly because once it does, there’s nothing you can do to stop the increasing bitterness! 

Also, the genetics of the broccoli matter, too: Some variations and even specific lineages are just more predisposed to bitterness than others. Though you can manage the bitterness in such plants, as we will learn, there is not much you can do if it is all in the genes!

We’ll look at all the possible stressors and other factors that produce bitter broccoli in the next section.

Factors that Make Broccoli Bitter

The following are some of the most likely factors and stressors that will cause your broccoli to turn bitter, or even cause it to bolt outright. Remember, you need to manage all of these factors as best you can if you want sweeter, crisp broccoli!

Too Hot: A big one.  If the temperature gets too hot, the plant will rapidly start to bolt and turn as bitter as can be. This is why it’s important to check your plating location and understand your growing zone before putting your broccoli in the ground.

Too Much Sun: Another big cause of bitterness, one that often gets new or inexperienced gardeners. Too much direct sunlight, even when temperatures are right, can also cause your broccoli to turn bitter, or possibly bolt.

The ideal would be about 6 hours of direct sunlight per day for most varieties, though many species do fine with even less.

Too Little Water: Another common cause of bitterness is too little water, or soil that is allowed to dry out. This stresses the plant and causes bitterness. Remember that your watering schedule is dependent on many factors, so pay attention to the personal needs of your plants. 

Incorrect Soil pH: The soil pH is also important; broccoli needs acidic soil, preferably with a pH of 6.0 and up.  If the soil pH is too high or too low, it will stress the plant and, yep, lead to bitterness.

Lack of Nitrogen: Another issue some gardeners might have with their broccoli plants is a lack of nitrogen in the soil. Too little nitrogen causes stunted growth and bitter flavor; if you suspect this might be an issue, try adding a slow release fertilizer or organic compost to your soil.

Overcrowding:  If your plants are overcrowded, they will compete with each other for reesources, and that will cause stress. Make sure each plant has plenty of space (usually at least 18”) between it and its neighbors in order to avoid this issue. 

Late Harvest: Bolting is not an ailment that strikes your broccoli, but a survival strategy. Plants that bolt are deciding to reproduce as early as they can. They’ll usually flower at the end of their normal lifecycle even in ideal conditions, which is why nailing the right time to harvest is always important.

If you wait to long to harvest your mature broccoli, it will be growing more and more bitter all the time. Harvest it as soon as it is ready for milder broccoli! 

So there you have it. Now that you know of all the possible causes of bitter broccoli, you can work to make sure that none of them occur in your garden. By managing these stressors, you should be able to get a sweeter broccoli harvest from your garden! 

But sometimes, by bad luck or something else, our broccoli is still just a little too bitter. Is there anything we can do about this bitter broc once it is picked?

Dealing with Bitter Broccoli

You need not throw away your hard-won broccoli just because it is a little bitter. It is still possible to make a fine meal of it with a few tricks.

One of the best ways to take the bitter bite out of broccoli is just to cook it at a lower temperature for slightly longer than usual.  This will help retain the flavor while reducing some of the bitterness. 

You can also add other flavors to your broccoli dishes that either complement or mask its bitter undertones, such as lemon or garlic.

These ingredients will help balance out the flavors in the dish, making it more palatable even if it is a bit too bitter. You can also try a little pinch of salt or sugar, even honey believe it or not, and some folks swear by a splash of vinegar.

Other standbys that pair well with broccoli and can help to tame bitterness are roasting it with a drizzle of olive oil and a dusting of fresh-grated parmesan cheese, or making a light dressing with olive oil, lemon juice and ginger finished with a few red pepper flakes.

But, there is a fine line: you should be cautious not to cook broccoli overly long , as this will amplify rather than reduce the bitterness.

If all else fails, you can also try turning your bitter broccoli into a savory soup or puree. The bitterness may still peek through, but it shouldn’t overpower the dish when it is finished.

I hope these tips will allow you to use and appreciate your broccoli even when it is a little to bitter for your taste.

26 thoughts on “Why Does Broccoli Grow Bitter?”

  1. I have a Square Foot Garden and just harvested my puny broccolis. I planted them May 19, and it had just finished snowing here in Canada. Anyway, I tasted it raw, it was so bitter! But I decided to go ahead cook them. I roasted them in the oven at 425 with olive oil, salt and sliced garlic. After they started getting charred I took them out and added lime juice and parmasean. They were just fine! Not the slightest bit bitter. Don’t throw it away! Roast it.

  2. I have found that the variety of lettuce that I plant has a lot to do with getting bitter. I found that Butter crunch lettuce never gets bitter in my garden, also, flashy back trout lettuce from Uprising seed co. doesn’t seem to get bitter. Still eating in August.

  3. Usually bitter lettuce is caused by not enough iron in the soil. You can get supplements to add to the soil. It could also be the cause of the bitter broccoli. And make sure you dont skimp on the watering.

  4. We have never had success with broccoli either. I have heard either early spring or fall so we tried both. Hoping to have better luck with fall.
    I can say that with cauliflower pinning the leaves over the heads worked WONDERS for making it more edible.

  5. Hi Kendra

    Alas, broccoli can be a pain. It is a fussy plant. Like all veggies variety and growing conditions, location and soil acidity need to be taken into account. A nice cross section of suggestions too.
    I find that it is best cooked, I prefer steaming for a few minutes as we like a crunch.
    However, manure the year before planting. Chicken manure is grand but the fresher, the higher the ammonia, this can effect taste in all veg. Rotate planting, only put the same variety in that spot every three years. One lady correctly raised the point of watering, another strong sun. Water a lot in dry conditions like yours and yes, cover the heads. Thought of old camo netting on a frame?

    Finally, it is a cold weather lover. It is like others of its kind and tastes better after a frost or two. In England folk tend to see it as a winter veg.
    If I may suggest, test the soil acidity, the meters are cheap. Aim for a neutral reading. You may need to add lime or more organic rotted material to adjust the acidity / alkalinity.
    Hope this helps!

    God bless


    • Thank you for your suggestions, John! I definitely think I need to focus on broccoli as a cold weather crop. It just gets so hot so quickly here in the South. I do need to test the soil, too. That’s one of those things I’ve been meaning to do from the very beginning!

      Blessings to you my friend.

  6. Same problem here this year, inedibly bitter when raw but after cooking, it was just fine. Some was blanched before freezing, some was stir fried or steamed but all that started out bitter when raw ended up delicious. We are in the South, don’t use pesticides, had to do the salt water soak because of the worms. The most productive variety we ever grew that never got bitter was Early Dividend.

  7. Now that you mention it, the broccoli I’ve nibbled on raw from my garden has been sorta bitter. But I haven’t thought much about it cause it cooks up fine. I steam it or use it in a stir fry.

  8. Definitely sounds like sporadic watering. The picture you have shows good tight heads but they’re yellowing. In the south, I’d plant middle summer so they’re ready to harvest in the cooler months, and keep the water level as even as possible. God bless the future harvests!

  9. Not enough water, too much sun…those would be my guesses.

    Like Connie said, tie the leaves over the heads to keep them cool. Nothing like keeping a cool head πŸ™‚

    It’s probably not too late to salvage the side heads by giving extra water.

    Good luck!

  10. When I plant broccoli – I use paper hats or pin up the leaves over the head with a clip to keep them out of the sun. I usually have very large wonderful heads… about 3 times the store bought size and no bitterness. Hope it helps.

  11. Well, mt broccoli tasted good. I hope you figure out the problem with yours. I might have to try containers next year for my lettuce. I really want some fresh salads, too.

  12. I did a little bit of research because I am still learning. What I read was
    1. Don’t plant in the same spot 2 years in a row.
    2. Broccoli should be planted in the summer and harvested in the fall when it’s cooler.
    People seemed to agree that heat can make it bitter. Cucumbers, too, apparently.

    Do you have chickens or pigs that might eat it?

  13. I don’t know but I searched and came up with;

    A rise in the temperature of sun’s heat and the hot rays falling directly on the vegetable makes it to turn bitter.

    The acid level of the soil can also cause bitterness.

    Any stress on a vegetable such as high temperature, low moisture, low fertility, or foliage disease can cause bitterness.

    When my broccoli florets were at the bitter stage, the peeled stems were still delish!

    Good luck and when you find the answer, tell us.

  14. I’m getting ready to harvest my broccoli. If you find the answer let me know, I might need an answer, too. I didn’t know broccoli could be bitter, I hope mine isn’t. My lettuce, for the second year in a row, has been bitter, and it hasn’t even bolted yet. I don’t know what I am doing to not be able to grow some yummy lettuce. I have a whole row of mixed lettuce that is inedible, so I know the frustration.

    • Ashlee,

      Every bit of my lettuce was bitter last year. This year I planted it in containers, and moved them into the greenhouse. NONE of it has been bitter!! I think it’s ’cause it isn’t in direct sunlight. I’ve had to keep them watered a lot ’cause it gets really hot in there, but it has been really nice being able to enjoy fresh salads, finally!!

      The chickens are always glad to help take care of anything I deem inedible.

  15. Howdy, do you use pesticide? If not do you have worms in the heads? Both can make yours taste bitter. I use diatomaceus earth, no bugs no worms. I have been told to soak the green heads in cold water for an hour before cooking, worms will float to the top (if you have them). If you wait too long to cut the heads, they bloom and go to seed, very bitter.How are you cooking yours? Might be for too long. Broccoli is more of a cold weather veggie. Might want to stop and plant again for the fall.Good Luck.

    • Ruthlynn,

      No pesticides. We used floating row covers, and planted peppermint to discourage the white moths that bring worms. We had a few, but not nearly as bad of a problem as last year. I soak my broccoli in cold salt water for a while to kill all of the worms. I hadn’t cooked the broccoli yet. I’ve just been trying to eat it raw. Thanks though!

  16. Something I’ve discovered about broccoli is that the leaves are even more nutritious than the heads (which I don’t like very much, anyways). So, I have been harvesting the leaves all spring/summer and adding them to green smoothies or dehydrating and powdering them (like this: to use in smoothies throughout the fall and winter. I am up to a gallon of greens from outer cabbage leaves, broccoli leaves, kale, and spinach grown organically in my urban garden this year!

    Since I know you also like using all of the parts of what you grow, thought I would share πŸ™‚

    • I see that you wrote this 5 years ago so I hope you remember giving this advice. I’m impressed with your drying and powdering broccoli leaves idea. Can I just ask how you did that? Did you use a dehydrator and then pulse the dried leaves in a food processor? And do you know how your powder relates (in nutrition) to a store brand such as Greens?


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