How To Grow Broccoli

The secret to the best-tasting broccoli is in the seasoning—not the spices, mind you, but the time of year. Broccoli that matures during cool weather produces healthy heads that are sweeter tasting than those you pick at any other time. Grow it this fall, and you will enjoy the most tender and flavorful broccoli you've ever eaten—long after the summer garden is a memory.

Broccoli grows best in fall because spring conditions may be unpredictable. Long, cool springs, for example, cause young transplants to form small, early heads; if temperatures heat up early in spring, heat-stressed broccoli opens its flower buds prematurely. And high temperatures as broccoli matures can cause bitter, loose heads to form, leaving you with smaller and less tasty florets. In fall, broccoli produces bigger and tastier heads, as plants mature during cooler weather.

Broccoli Basics

When to Plant

You can easily figure the perfect time to plant broccoli seeds this fall. If you want to sow seeds directly in the garden, do so about 85 to 100 days before the average first fall frost in your area, which happens in mid to late summer in most places. If you prefer to grow from transplants, figure the date for getting your plants in the ground by adding 10 days to the "days to maturity" for the variety you're growing, and then counting backwards from your expected first fall frost date.

Where to Plant

Broccoli grows best in full sun and where the soil is slightly acidic (pH between 6.0 and 6.8), fertile, and well-drained, yet consistently moist and rich in organic matter. The right pH and the organic matter help ensure that nutrients, particularly essential micronutrients like boron, are readily available. (A boron deficiency can cause broccoli to develop hollow stems, but adding too much is toxic to plants, so a soil test is essential.)

Fall broccoli has specific spacing requirements. If you're gardening intensively in a raised bed, space your plants 15 to 18 inches apart; for gardening in rows, set the transplants 18 to 24 inches apart within the row and space the rows 24 to 36 inches apart. Be sure to set transplants slightly deeper in the ground than they were in the pot.

Keep Them Nourished 

Broccoli is a moderately heavy feeder, so work in 2 to 4 inches of rich compost or a thin layer of well-aged manure before planting. Rabbit manure is a personal favorite, though most any aged manure or compost produces big and tasty heads. After you've harvested a plant's central head, you can encourage extended side-shoot production by scratching a little nitrogen-rich fertilizer such as fish meal or aged manure into the soil around its base (this is known as side dressing). The best time to side dress sprouting types that have overwintered is in late winter or early spring when growth resumes.

Shelter from Cold

Freezing temperatures can cause chilling injury that turns buds purple and sometimes softens heads, though they are still good to eat. I've had broccoli freeze solid, and when it thawed out it was fine.  Just don't let heads freeze and thaw repeatedly.

Offer cold-weather protection with floating row covers, which provide an additional 4 to 8°F worth of warmth, shielding harvests from heavy freezes and extending the season by up to four weeks. Or cover broccoli with tunnels or a cold frame, which can boost daytime temperatures by 10 to 30°F.

Protect Against Pests

Row covers provide some protection from pest insects, but the best protection is to grow healthy plants—and that begins with healthy soil. Insect pests are generally less prevalent in fall than in spring. But if your broccoli does suffer an infestation of destructive caterpillar pests such as cabbage loopers, you can control them with Bacillus thuringiensis var. kurstaki, a naturally occurring bacteria that stops the pests from chewing but is harmless to beneficial insects.

Harvest Hints

For best flavor, harvest broccoli heads while the buds are just starting to swell but before the yellow petals start to show. Keep an eye on the head, for when it begins to spread open, the individual buds start to flower. Harvest the central head by cutting the stalk at a slant, about 5 to 8 inches below the head. This encourages side-shoot production for continued harvests. It’s important to harvest broccoli in the morning before the plants heat up, because broccoli has a really high respiration rate. Once the heat sets in, you need to cool it down quickly, or it's not going to hold up well and taste like it should.