How to Grow Broccoli

Cool-season timing

Broccoli grows best and yields most when temperatures do not exceed 75°F, and hardened plants survive down to 28°F, so it belongs in the cool shoulders of the year. Set transplants out 2 to 3 weeks before the last frost-free date for a spring crop; for a fall crop, plant 50 to 75 days before your anticipated maturity date.

If you start your own, sow seed a quarter to a half inch deep. Space plants 12 to 18 inches apart in the row with rows 2 to 3 feet apart. The when-to-plant-broccoli and broccoli-spacing calculators answer timing and layout on their own.

Varieties differ in speed — Packman at about 50 days, Green Comet at 55, Premium Crop at 65 — so matching a fast variety to a short cool window helps in hot climates.

Water, feeding, and heat problems

Broccoli needs 1 to 2 inches of water per week; the how-often-to-water-broccoli calculator gives the readout on its own. Steady water and nitrogen are also what fuel the side-shoot crop later.

Apply nitrogen fertilizer about 4 weeks after transplanting, again when the head reaches quarter size, and again after the main harvest to push side shoots. The best-fertilizer-for-broccoli calculator covers feeding.

High summer temperatures reduce growth, decrease quality, and cause loose heads that taste bitter. Buttoning — premature tiny heads — comes from cold exposure or from water or nutrient stress; the broccoli-not-forming-a-head diagnostic sorts out which.

Harvesting the head and the shoots

Harvest the central head when it is large and compact, 6 to 12 inches in diameter, but before the flower buds begin to open. Waiting too long lets the buds yellow and flower, which is a quality loss.

After you cut the main head, keep watering and feeding. The plant produces many 3 to 6 inch long side shoots, so a single broccoli plant keeps giving for weeks past the first harvest.

The when-to-harvest-broccoli calculator gives the head-timing readout, and if you plan to interplant, can-you-plant-tomatoes-with-broccoli covers that pairing.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• Utah State University Extension — Broccoli in the Garden — Broccoli is a cool-season vegetable that grows best and produces highest yields when temperatures do not exceed 75°F and can survive down to 28°F; transplants may be planted 2-3 weeks before the last frost-free date, and fall crops planted 50-75 days before anticipated maturity; plant seeds 1/4-1/2 inch deep and space plants 12-18 inches apart in rows 2-3 feet apart; recommended varieties include Packman (50 days), Green Comet (55 days), and Premium Crop (65 days); harvest when heads are large and compact, 6-12 inches in diameter, but before the flower buds open, after which plants produce many 3-6 inch side shoots with continued fertilizer and water; high summer temperatures reduce growth, decrease quality, and cause loose bitter heads, and buttoning occurs from cold exposure or water/nutrient stress; require 1-2 inches of water per week and nitrogen at 4 weeks post-transplant, at quarter-sized head, and after main harvest.

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