How Big Do Broccoli Plants Get?


If you are growing broccoli for the first time, or you got small plants last year, you might be wondering how big broccoli plants can get.  I wanted to know the same thing, so I did some research to find out how tall and wide broccoli plants can get, and how large broccoli heads can grow.

So, how big do broccoli plants get?  Broccoli plants can grow 18 to 30 inches (46 to 76 centimeters) tall and up to 18 inches (46 centimeters) wide.  The central head of broccoli can grow as large as 8 inches (20 centimeters) in diameter, but most are 4 to 6 inches (10 to 15 centimeters) in diameter.  The side shoots that grow after the main head of broccoli is cut can be 4 to 7 inches (10 to 18 centimeters) tall, but they will only be 1 to 2 inches (2.5 to 5 centimeters) in diameter.

Of course, the size of broccoli depends not only on the variety that you plant, but also on growing conditions.  Let’s start off by taking a look at some of the broccoli varieties you can choose from.  Then we’ll get into steps you can take to grow bigger broccoli plants, no matter the variety.

How Big Do Broccoli Plants Get?

As mentioned before, the size of broccoli plants can vary quite a bit, depending on the variety and growing conditions.  Let’s look at the height, width, head size, and side shoot size of a few broccoli plant varieties.

Broccoli Plant Height

Broccoli plants can range from 18 inches to 30 inches tall when fully grown.  Some varieties from Bonnie plants include:

Note that the first three varieties listed (Belstar, Lieutenant, and Green Magic) focus their energy on producing a large, central head of broccoli.  These varieties will grow secondary side shoots after the main head is harvested, but they are smaller and not the “main attraction”.

broccoli plant
This head of broccoli is the central head, and can reach 8 inches in diameter.

 On the other hand, the last variety on our list (Artwork Stir-Fry) focuses its energy on producing only side shoots.  Of course, a “main” head will still grow, but you are encouraged to pinch it off at 1 inch (2.5 centimeters) in diameter to encourage side shoot growth.

Broccoli Plant Width

Broccoli plants can grow up to 18 inches (46 centimeters) wide, which is in some cases as tall as the plant will get.  As a result, it is recommended to leave 18 inches (46 centimeters) between broccoli plants.

This allows enough room so that adjacent broccoli plants do not compete for water or nutrients.  It also prevents diseases or pests from spreading rapidly between plants.

Of course, some broccoli varieties will be much narrower.  For instance, the organic “Belstar” variety will only grow 10 to 18 inches wide.

Broccoli Head Size (Diameter)

When most people hear the word “broccoli”, they think of the large heads of broccoli on display in a supermarket produce section.  These large heads come from the main or central head on a broccoli plant.

broccoli head
A head of broccoli can get up to 8 inches in diameter, but most are 4 to 6 inches in diameter.

Some plants can grow a central head with a diameter up to 8 inches!  However, most broccoli plants will grow a central head with a diameter of 4 to 6 inches.

Of course, it is important to remember that quality is more important than size.  You should not allow a head of broccoli to “over-ripen” just so that it can get larger.  Otherwise, the flavor will be bitter and the vegetable will not be enjoyable to eat.

When you harvest a central head of broccoli, it should be dark green, with its buds tightly packed together.  If the buds start to spread out or turn yellow, then the broccoli plant is starting to “bolt”, and the head should be harvested immediately.

When a broccoli plant bolts, it is preparing to grow flowers and produce seeds.  Once this happens, the plant will think that its work in life is done, and it may quickly stop producing heads.

flowering broccoli
This broccoli has bolted (it is starting to flower and produce seeds).

To keep a broccoli plant from bolting so that it continues to produce heads, be sure to harvest regularly.   That way, the plant can keep producing side shoots even after the central head is harvested.

For more information, check out my article on broccoli bolting.

Broccoli Side Shoot Size (Height and Diameter)

As you can guess, the side shoots on broccoli have heads that are smaller than the central head.  Side shoots will have heads that are only 1 to 2 inches in diameter.

However, these side shoots can still grow fairly tall.  In some cases, broccoli side shoots can grow to a height of 4 to 7 inches.  These tall, thin side shoots can make a great garnish for many dishes, or they could go right into a stir-fry.

How To Grow Bigger Broccoli Plants

The size of your broccoli plant and heads will depend in part on the variety you choose to grow.  Beyond that, it’s up to you to provide the proper care so that your broccoli plants can grow to their full potential.  Here are a few tips to help your broccoli plants to grow taller and produce larger heads.

Soil pH and Nutrition For Broccoli Plants

Broccoli plants prefer a soil pH that is between 6.0 and 7.0 (slightly neutral to acidic).  Outside of this range, your broccoli plant may have trouble absorbing nutrients from the soil through its roots.

Even if pH levels are correct, you can still encounter problems if there is a nutrient deficiency in your soil.  Using compost or fertilizers that supplement NPK (nitrogen, phosphorus, and potassium) and other nutrients will help to prevent growth problems.  For more information, check out my article on how to make compost.

compost bin
Compost is a good way to provide organic material and nutrients to broccoli plants.

If you aren’t sure about the pH or nutrient levels in your soil, the first step is to do a soil test.  To learn about how you can do a soil test, check out my article on soil testing.

A soil test will tell you the pH of your soil, along with the levels of various nutrients.  For more information, check out my article on what a soil test tells you.

If you send your soil to the lab at a local agricultural extension, you will get more detailed test results than a DIY home test kit could give you.  Just make sure to tell them what you are growing, and they will send back detailed suggestions on how to treat your soil.

Make sure to do a soil test before adding any lime, sulfur, or other amendments to your soil.  This will help to ensure that you don’t end up with excessive nutrients or an imbalanced pH.

For more information, check out my article on over fertilizing your plants.

Sunlight and Temperature For Broccoli Plants

Broccoli plants want full sunlight, preferring to get 6 or more hours of full sun per day.  Broccoli is also a cool weather crop, meaning that it prefers temperatures between 65 and 80 degrees Fahrenheit (18.3 to 26.7 Celsius).

sunlight through forest
Broccoli prefers 6 or more hours of direct sunlight per day, so give them a sunny spot in the garden.

If temperatures get too hot, then broccoli plants are more likely to bolt (start producing flowers and seeds) early in the growing season.  If this happens too early, then you may not get a large central head, or any head at all.

To prevent bolting due to heat, use mulch on top of the soil around your broccoli plants.  Not only will this keep the soil from getting too hot, but it will also suppress weed growth and retain water in the soil.

You may be able to manage two plantings of broccoli per year: one in the spring, and one in the fall.  Since broccoli prefers cool weather, you may want to do a fall planting in warmer climates.

When planting broccoli in the spring, check the last frost dates to avoid planting too early.  For more information, check out this article on frost dates from the Old Farmer’s Almanac.

Watering and Weeding For Broccoli Plants

When watering your broccoli plants, avoid watering from above.  Instead, water close to the ground, and don’t get the leaves or broccoli heads wet.  If you get the heads wet, you invite mold and other diseases to your garden. For more information on how much to water, check out my article on over watering your plants.

water
Make sure not to water your broccoli plants from above, or else you have a higher risk of mold or other diseases.

As mentioned earlier, using mulch such as grass clippings, leaves, or wood chips will help to prevent weed growth.  You can even cover weeds that are already growing, which will often smother them due to heat and lack of air.

Spacing For Broccoli Plants

Broccoli plants should be spaced 18 to 24 inches (46 to 61 centimeters) apart, since they can grow to a width of 18 inches.  You don’t want the broccoli plants to be touching, since this allows diseases to spread more easily through your garden.

You should place your rows about 24 inches (46 centimeters) apart, which will give you plenty of room between rows so that you can comfortably pull weeds or water, fertilize, and harvest your broccoli.

Common Questions About Broccoli Plants

There are a couple of common questions about growing broccoli that should be addressed, so let’s get to them now.

How Long Does Broccoli Take To Grow?

The days to maturity (time from seed to harvest) for broccoli plants varies quite a bit, depending on both the variety and the growing conditions.

broccoli head
Broccoli can take from 37 to 200 days to mature, although most head broccoli take longer than broccoli grown for thin, small shoots.

Some broccoli varieties can take as long as 200 days to mature, such as the Purple Sprouting Broccoli from Burpee.

However, other varieties of broccoli can mature in only 37 days, such as the Sprouting Broccoli Burgundy Hybrid from Burpee.

Here are some growing times for some of the varieties we mentioned earlier:

  • Belstar (Organic) – matures 66 days after planting.
  • Lieutenant – matures 55 to 65 days after planting.
  • Green Magic – matures 57 days after planting.
  • Artwork StirFry – matures 55 days after planting.

As you can see, most of these varieties mature 8 to 10 weeks (about 2 months) after planting. 

How Many Heads of Broccoli Do You Get From One Broccoli Plant?

Generally you will get one large central head from a broccoli plant.  However, you can get multiple smaller side shoots if you keep harvesting before the plant bolts (produces flowers and seeds).

Conclusion

By now, you should have a better idea of how big broccoli plants can get.  You also have some tips on how to help broccoli plants to grow to their full potential.

I hope that this article was helpful – if so, please share it with someone who can use the information.  If you have any questions or advice of your own about growing broccoli, please leave a comment below.

jonathon.david.madore

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

Recent Content