Updated date:

How to Grow Broccoli, a Cool Season Vegetable

Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.

how-to-grow-broccoli-a-cool-season-vegetable

What is Broccoli?

Broccoli (Brassica oleracea var. italica) is actually a biennial that we grow as an annual. It is native to southern Italy. It spread to Northern Europe by the 18th century, then was brought to North America in the 19th century by immigrants from Italy.

Broccoli is related to cabbage, cauliflower, collard, kale, kohlrabi and Brussel sprouts. All of these plants can cross-pollinate. There are also different types of broccoli, but the one that most of us are familiar with and grow in our gardens is called Calabrese broccoli. It gets its name from Calabria, Italy where it was developed.

Broccoli is a cool season plant that grows best in 65°F to 70°F. Most gardeners grow broccoli in the spring for an early summer harvest.

How to Prepare Your Garden to Grow Broccoli

Broccoli needs to be grown in full sun which is a minimum of 6 to 8 hours per day. The optimal amount of daily sunlight is 8 – 10 hours. If your plants don’t get enough sun, they will be leggy and the heads will be smaller.

The best soil is rich, well-drained soil with a pH that is slightly acidic, 6.0 – 7.0. Get a soil test done on your garden soil in the fall before planting your broccoli. A soil test will tell you the pH and nutrient levels and what amendments you need to add. Soil tests are done in the fall so that the amendments can be added and have several months to penetrate the soil.

If left unharvested, the buds on the head will open into yellow flowers.

If left unharvested, the buds on the head will open into yellow flowers.

How to Grow Broccoli From Seed

Indoors

Start your seeds indoors 6 – 8 weeks before your last frost. Plant the seeds ½ - ¾ inch deep. Keep the soil moist. You can use a heat mat set to 75°F but it is not necessary. The seeds will germinate in soil that is as cold as 40°F. Germination should occur in 4 – 7 days. Remove the heat mat when your seeds have germinated.

You can transplant your seedlings outdoor when they have 4 – 5 true leaves, about 4 – 6 weeks after germination. Space them 18 inches apart. Don’t worry if the weather is still cold. The plants can withstand a light frost. Just cover them with a floating row cover if a frost is predicted.

Outdoors

Start your seeds in your garden 4 weeks before your last frost. Plant the seeds ½ - ¾ inch deep and 3 inches apart. Keep the soil moist. Don’t worry about the soil temperature. The seed will germinate in soil that is as cold as 40°F. Germination should occur in 4 – 7 days. After germination, thin the seedlings to 18 inches apart.

The seedlings can withstand a light frost. If a frost is predicted, cover your seedlings with a floating row cover to protect them.

How to Care for Broccoli

If you purchase your broccoli as starts from your local nursery, plant them slightly deeper than they were in their pots, 18 inches apart.

Broccoli has a very shallow root system. Surround your plants with a thick layer of mulch which will keep the weeds down. If weeds do get a foothold, instead of pulling them out and possibly disturbing the roots of your broccoli, cut the weeds down at the soil level. They will grow back but if you cut them down enough times, eventually the roots will die.

Mulch will also help keep the soil moist. Broccoli needs 1 – 1 ½ inches of water each week. Drip irrigation is best. If water gets on the heads of your plants, it could cause them to rot.

Fertilize your seedlings 3 weeks after planting with a high nitrogen fertilizer. Fish emulsion is best. If the bottom leaves of your plant start to turn yellow, it is a sign that your plants aren’t getting enough nitrogen. ¼ cup per plant of blood meal should solve the problem.

Blood meal is just as awful as it sounds. It is the dried blood of animals that have been slaughtered for their meat, usually cattle. It is very high in nitrogen and comes in powdered form. Just scratch it into the soil around your plants to give them a boost of nitrogen.

Smaller heads will grow from the sides of your plant.

Smaller heads will grow from the sides of your plant.

How to Harvest Broccoli

The green head of the broccoli that we eat is actually the buds of the plants’ flowers. If left on the plants, they will open into small yellow flowers.

Homegrown broccoli will not get as big as the broccoli that you see in the stores. Harvest yours when the heads are the size of a fist or if you see the yellow flowers start to open.

Harvesting is best done in the morning. Cut the head from the plant using a sharp knife. Cut about 6 inches of stem off. Always cut on the diagonal so that water won’t pool in the top of the plant, rotting the heads that will form later.

After you have harvested the large main head, smaller heads will form along the sides of the plants. They will not grow as large as the main head. Try to harvest them before the flowers open.

How to Store Broccoli

Broccoli can be stored in your refrigerator for 5 days. Or you can blanch it and then freeze it for up to one year.

To blanch your broccoli, cut it up into florets. Boil the florets in boiling water for 1 – 2 minutes, then immediately remove and put into an ice bath to stop the cooking.

© 2021 Caren White

Comments

Caren White (author) on February 15, 2021:

You're very welcome! Homegrown broccoli always tastes better than broccoli purchased at the store.

Chitrangada Sharan from New Delhi, India on February 14, 2021:

Broccoli is almost regular in our family foods, these days. It’s good in taste and nutritious too. I will follow your tips and try to grow some of our own.

Thank you for sharing this informative article.

Peggy Woods from Houston, Texas on February 13, 2021:

I have never tried growing broccoli but do enjoy eating it. Thanks for the planting tips.

Imogen French from Southwest England on February 13, 2021:

Some great tips there. I have grown summer and autumn broccoli in the last year, and am just waiting for my purple sprouting broccoli to bud up. Definitely one of my favourites

Caren White (author) on February 13, 2021:

Thank you, Pamela! I hope that the information I provided will lend success to your garden.

Pamela Oglesby from Sunny Florida on February 12, 2021:

Broccoli is probably my favorite green vegetable. I appreciate all your advice as to how to grow broccoli, Carn. This is an excellent article.