Garden Blog

How to Grow Broccoli

How to Grow Broccoli

Broccoli can be tricky to grow, but with a little practice, and a few helpful tips, you can grow the best broccoli you've ever eaten! 

Crop Description:

Homegrown broccoli is a tasty thing of beauty. With tender buds, stems that are firm and crisp, and leaves that can be sautéed up or thrown into smoothies, you can’t go wrong. Broccoli can even be grown as a winter crop in areas with mild winters, generally USDA zone 7 and above. In areas with long, cool springs or late fall freezes, you should choose varieties that are slow to mature. In other areas, choose the faster-maturing varieties. It is also an excellent natural source of vitamins A and C, potassium, calcium, and is very high in fiber.

While broccoli can look vastly different from one variety to the next, unlike other crops with wide variety, broccoli tends to taste very similar. While more selection and breeding is creating more exceptions to this rule, right now, the most common rule breaker you are likely to run into is Romanesco. Romanesco grows a large, central head of bright chartreuse-colored florets and has a sweeter flavor than other varieties.


Planting and Aftercare:

Fill individual pots with your favorite seed starting medium six to eight weeks before your last frost date. In areas with mild winters, you can start earlier and set out under floating row covers with the plants are about eight weeks old. Sow three seeds per pot, about ¼” deep. Moisten well.

Cover pots with plastic, or the greenhouse cover of your seed starting tray and set in a warm, shaded area. When seeds sprout, move your flat to under your grow lights and remove plastic covering. Avoid letting delicate sprouts dry out. When plants have their first true set of leaves, thin them to the one strongest seedling per pot. If you didn’t do it the previous fall, dig a couple inches of good compost into your planting bed in preparation for transplanting.

All seedlings need special care to “harden them off” before planting outside. Hardening off refers to the time you’ll spend acclimating your seedlings from inside to outside. This is best done gradually, a couple hours in shade the first day, then bringing them back inside. The next day, shoot for 4-5 hours with one of those hours in full sun. From then on, you’re increasing the amount of sunlight during the day, until by the end of a week you should have them used to a full days sunlight. Nighttime is a little trickier with spring crops because you may have to add frost protection, but the principle is the same: gradual acclimation.

When transplanting outside in your garden beds, pay careful attention to your variety’s specific mature growth size. This can vary widely with broccolis depending on type. Make sure you leave enough space between each plant as over-crowding can lead to smaller heads and increased bug pressure.

Tips for Success:

As always, buying and starting from seed will get you the best and most interesting variety selections and control over growing conditions. If you decide to purchase started plants, choose healthy looking plants that have at least two sets of leaves. Avoid plants that are clearly too big for their pots because these plants could be pre-stressed. Check the undersides of the leaves for aphids, and flick the leaves and if flying insects emerge from the plant, don’t buy it.

Covering young plants with a floating row cover not only extends your season, but it also might be your best defense against Brassica loving pests.

Mulch with compost, shredded leaves, or rotting straw when plants are about 6” tall. Keeping the plants well-watered throughout the season will help lessen environmental stresses that could cause your broccoli to bolt and flower too early.

To harvest, cut off the central head and about 4-6” of stem. In a few weeks, the broccoli plant will grow smaller heads on its side shoots. You can generally get two respectable harvests of side shoots after the initial crown cutting before the plant starts to become too tough and bitter and should be pulled to make room for something else.

Trouble to Watch For:

Small, tough heads are often caused by a lack of essential minerals in the soil. Add c when planting broccoli to increase the levels of calcium and magnesium available to the growing plants.

Stunted heads may be due to a repeated lack of water. Broccoli (and many Brassicas) are shallow-rooted and dry out quickly. Mulch well to retain moisture. Water frequently, especially during hot weather..

Non-existent heads are a bit trickier to diagnose, but I’ve found they’re usually due to excess nitrogen in the soil, or from summer giving spring the boot sooner than it should. Sometimes this makes the plants bolt seemingly overnight, and sometimes it just stunts their growth.

Cutworms are fat, green, 1 ½” long, fantastically camouflaged, pests. They chew on the area at the top of the broccoli’s roots and on leaves. Place a collar (a cat food can with both ends removed works well) around seedlings to protect them. Remove the collar once the plants are established.

Cabbage Loopers, also known simply as Cabbage Worms, are thin, green caterpillars that chew large, ragged holes in leaves. Cover plants with floating row covers, handpick caterpillars, or spray plants with BT to control them. As with any pesticide, even the organic ones, make sure to follow the directions on the packaging!

Good news, your chickens will LOVE the worms you picked for them! Or you can just squish them.

Growing Zone and Special Conditions:

Broccoli is an annual vegetable that thrives in full sun and cool weather. In warm weather, it is much more tolerant of shade. Broccoli grows best in a soil that is enriched with plenty of organic matter, such as your homemade compost or well-rotted manure.

Harvest heads promptly when they reach an optimum size but before tight buds start to loosen. When you see this, the yellow flowers are not far behind and the broccoli will likely be too bitter to eat.

After harvesting, soaking the heads in cold water will force out any insects that might be hiding, and help keep the flavor fresh and assist in the heads staying crisp in your refrigerator for at least a week.

Broccoli freezes beautifully for winter use, and dehydrates well for soups and stews. If you are lucky enough to have a root cellar, or can replicate the conditions of one in your basement, you may be able to store certain varieties for quite a long time.


 Written by Sow True Seed's Education Director, Angie Lavezzo.