Broccoli

Broccoli, a member of the Brassicaceae (cabbage) family, has been under cultivation in Europe for centuries, but it wasn’t until It was the 1920’s that it was planted as a commercial crop in California where it is now grown nearly exclusively. In home gardens, broccoli is grown as a cool weather crop.

Choices

Opt for varieties such as ‘Calabrese’, ‘Green Comet’, and ‘De Cicco’ for up to 3 months of extended harvest of side shoots; or choose ‘Green Comet’ and ‘Green Magic’ for large heads.
Plant ‘Cruiser’ and ‘Packman’ for fast growth to maturity.
Choose lime green Romanesco hybrid ‘Minaret’ with fractal arrangement for small heads, often only about 5 ½ in. This variety does not develop side shoots, but grows a single, dense head quite like a cauliflower. Other Romanescos may produce large heads.
Plant ‘Spigariello’, a leaf-broccoli cross between broccoli and kale, for distinctive blue-green, edible foliage on stems 3-4 ft. tall that only rarely produce a tiny head. Pick leaves at any stage of the plant’s growth.
Avoid name confusion with similar plants such as broccoli raab, also called rapini, a member of the mustard family; and broccolini, a cross between broccoli and Chinese broccoli.

Culture

Plan on 60-100 days for broccoli to mature, depending on time of seeding or transplanting, time of year, and variety planted.
Sow seeds March-April, transplant April-May to harvest before summer heat. Seed July to mid-August, transplant August- Begin one month earlier when seeding indoors.
Plant seeds ¼-½ in. deep and ½ in. apart in seed trays where there is ample light and warmth.
Transplant seedlings after six weeks. Stunting may occur if transplants are older, yielding only small heads. Temperatures near freezing may stunt young plants. Very high temperatures cause early bolting with flower stalks that will quickly bloom and go to seed.
Space plants 12-18 in. or more apart to allow for wide branching and root development.
Provide regular water, about an inch each week for consistent growth and large heads.
Side dress with compost or a complete organic fertilizer as plants grow and cover soil with a layer of organic mulch to suppress weeds and retain moisture.
Pick firm, dense heads before florets divide or begin flowering. Harvesting the central head stimulates side shoots to develop on side-sprouting varieties. Non-sprouting varieties do not produce side shoots. Plants will cease production once heads overly mature.

Problems

Plants will bolt before forming dense heads and go to seed in hot weather.
Avoid planting broccoli or other cabbage family crops in the same bed year after year. Crop rotation every year or two prevents soil-borne diseases.
Recognize signs of stress, such as stunted growth and small heads, caused by inadequate water, too much heat or cold, or poor soil.
Stay alert for chewing and sucking insects. Caterpillars and worms can be treated with organic treatments such as Bacillus thuringiensis (Bt), or handpick these and chewing insects such as harlequin bugs.
Use insecticidal soap or a strong jet of a garden hose so displace aphids or cover transplants with row covers to shield them from insect damage as well as low or high temperatures.

Additional Information

February 2022