Broccoli, a biennial most commonly grown as an annual, is a must-have for gardeners in any climate. A member of the cabbage family, it’s unsurprising that broccoli might have been bred from a cabbage plant thousands of years ago. Today, it’s one of the most popular vegetables in the US and is grown in almost every state, with particularly large volumes coming out of California. Although different varieties of broccoli vary in size and shape, almost all are greenish-blue in color with an occasional purplish-green crown and have heads 3–6″ in diameter at maturity.
Green Sprouting Calabrese broccoli is an old fashioned heirloom variety that develops small, bluish-green central heads followed by multiple side shoots that are harvestable until the plant is killed by a hard frost. Good for either spring or fall sowing, plants can get up to 3′ tall and can survive colder temperatures than some other types of broccoli.
Seed Depth: 1/4″
Space Between Plants: 12–18″
Space Between Rows: 24–30″
Germination Soil Temperature: 50–65°F
Days for Germination: 4–10
Sow Indoors: 5–9 weeks before average last frost date.
Sow Outdoors: 2–3 weeks before average last frost date or as soon as soil is workable.
Vegetative: Can be propagated by planting side shoots directly in soil or a mix of perlite and well-rotted compost or manure.
Prefers more moderate climates with temperatures of around 60 to 65°F. In areas with frosty winters, start in the spring for summer harvest or late summer for a fall harvest. Plant seeds in the fall for a winter or early spring harvest in warmer areas. Be aware of starting seeds too early in the fall or too late in the spring as extreme summer heat will stunt head growth if the plants have not yet matured.
Natural: Full sun.
Artificial: While growing broccoli inside is not recommended, if you are starting your plants inside, be sure that they are given adequate light: about 8–10 hours of light per day. Most indoor lighting systems such as HID or fluorescent are sufficient, but take care to allow ample space between the lamp and plants to avoid burning.
Soil: Prefers sandy to loamy soil with high amounts of organic matter. A pH of 6.0 to 7.0 will keep plants healthy and nourished.
Soilless: Start seeds or grow container plants in a soilless mix of perlite with well-rotted manure or coco coir.
Hydroponics: Will thrive in a hydroponic environment.
Aeroponics: Will thrive in an aeroponic environment.
Water: Requires low to moderate levels of water. Aim for 1–1.5 inches of water per week, depending on natural precipitation. Be sure to keep soil relatively moist but don’t overwater! If planting outside, drip irrigation systems will be most suitable.
Nutrients: Requires moderate to high levels of nutrients. Although not necessary, a standard, balanced fertilizer can be helpful to young plants approximately 3 weeks after transplanting. Decrease or stop feeding as head formation begins. If your soil is particularly acidic, add lime and calcium to raise the pH.
Foliar: Plants may benefit from foliar sprays containing boron, calcium, manganese, magnesium, molybdenum, and/or copper depending on your soil conditions. Broccoli will also benefit from a monthly feeding of liquid seaweed.
Pruning: Be sure to harvest heads at the correct time as this will keep your plants producing side shoots longer.
Mulching: Use mulch to suppress weeds and keep soil cool and moist.
Deficiency(s): Plant will begin to turn yellow towards the top of the leaves when they are nitrogen deficient. If this happens, use a standard nitrogen fertilizer or blood meal to regain plant health. Micronutrient deficiencies of calcium and boron will cause tip burn and hollow stems, respectively.
Rotation: A 3- to 4-year rotation away from all crops in the brassica family is recommended to help prevent pest and disease issues.
Companions: Grows well with beets, bush beans, carrots, celery, chard, cucumber, dill, kale, lettuce, mint, nasturtium, onion family plants, oregano, potato, rosemary, sage, and spinach. Avoid nightshade family plants, pole beans, rue, mustard greens, grapes, and strawberries.
Harvest: Crowns are ready to harvest when the flower buds are visible but have not yet started to separate from each other or open. If you’ve waited too late and leaves or heads start to turn yellow, harvest immediately to promote side shoot formation. Continue to harvest these side shoots as they reach maturity. To cut, use a knife or clippers and sever the crown approximately 6″ down on the stalk. Leaves may be harvested at any time throughout the growing season, just don’t take more than 1/3 of the leafy growth at a time.
Storage: Can be stored in the refrigerator for up to two weeks. Frozen broccoli will last for several months.
History: Named after the Calabria region of southwest Italy, this heirloom broccoli variety was brought to America by Italian immigrants in the late 1800s.
Preserve: Best eaten fresh. Broccoli may also be blanched and frozen.
Prepare: A versatile vegetable, broccoli may be steamed, sautéed, baked, or added to any variety of soups or stews. To cook, trim off the leaves and stem bottoms and use the crowns in your favorite recipes. Leaves and stems are also edible.
Nutritional: High in vitamin C and carotenoids. Broccoli is also rich in various compounds that have been associated with reducing the risk of cancer. Note that nutritional content is leached from the plant if it’s overcooked, so for maximum health benefits, eat your broccoli raw or lightly steamed!
Medicinal: Like its relatives in the brassica family, broccoli’s high antioxidant content makes it healthy for many of your body’s systems, as well as for overall health and longevity. These benefits of regular consumption include a lowered risk of diabetes, heart disease, and certain cancers.
Incorporate both the main head and side shoots of your plants in the tasty Raw Broccoli Raisin Salad.