How to Grow Broccoli: Answers to Frequently Asked Questions About Growing Broccoli, Storing Broccoli, and Cooking Broccoli

Broccoli
Broccoli, Image Courtesy of Satit_srihin, FreeDigitalPhotos.net

Broccoli requires a lot of space to grow, but gardeners are rewarded with produce that is far more flavourful and tender than supermarket broccoli. Young leaves and stems of the plants are also edible, but they require more cooking time to make them tender.

Broccoli is low in calories and very nutritious. It’s a source of protein, dietary fiber, vitamin C, beta carotene, calcium, iron, folate, and potassium, as well as a variety of additional phytochemicals that help to protect against cancer and other diseases.

When can I plant broccoli?

Start your broccoli indoors 6-10 weeks before the last anticipated frost and plant out in early spring (2-4 weeks before the last frost), or sow directly outdoors in the spring in a sunny spot in the garden 2-4 weeks before the last frost.  If you provide cold protection (such as a coldframe or mini hoop tunnel), you can sow directly outdoors 6-8 weeks before the last frost.

When transplanting, bury the stalks up to the base of the lowest leaves, as the plant will form more roots along the stalk portions that are under the soil. Transplants should be at least 4-5 inches tall with several sets of leaves when they go out. If you start your broccoli plants indoors, be sure to harden them off before transplanting.

To ensure a steady harvest, plant a mix of varieties that mature at different speeds or succession sow every 3-4 weeks.

You can direct sow a second broccoli crop in the summer (10-14 weeks before the first anticipated frost) to mature during the fall, or start the fall crop indoors 15-17 weeks before the first frost to reduce the risk of pest damage.

If your climate is very mild, you can even plant broccoli in the fall to harvest during the late fall, winter, or early spring. Your likelihood of success with cold-weather crops will be increased by growing cold tolerant varieties such as Marathon.

Broccoli does not do well in hot temperatures. The ideal temperature range for growing broccoli is 55-75 F/13-24 C.

How long does broccoli take to sprout?

Broccoli seeds will germinate in a temperature range of 40-85 F/4-29 C. This will take anywhere from 4-20 days, depending on temperature (warmer temperatures speed germination).

How far apart should I plant broccoli?

Leave 8 to 24 inches of space between broccoli plants. Minimum spacing will vary based on soil fertility – with very fertile soil, you can get away with closer spacing. However, wider spacing will usually produce larger broccoli heads.

Spacing between rows is typically 36 inches.

What type of soil does broccoli need?

Broccoli requires rich, well-drained soil. Mix a few inches of compost or well-rotted manure into the top 6-8 inches of soil before planting. Some sources recommend adding a balanced fertilizer when planting as well, particularly if your soil is nutrient poor.

The ideal soil pH for broccoli is between 6.0 and 7.5.

Can I grow broccoli in a container?

Yes, but you’ll need a very large container, and you’ll have to water more frequently because container soil dries out rapidly and broccoli needs a lot of moisture.

The minimum recommended container size for growing broccoli is 10 inches deep and 5 gallons of capacity (typically 12 inches in diameter for pots of average proportions).

Can I grow broccoli in the shade?

Broccoli plants do better in full sun (6 hours or more of direct sunlight per day). They can tolerate a bit of shade, but will mature more slowly without full sun.

Should I fertilize broccoli plants?

Broccoli is a big feeder, so you’ll probably need to add some extra nutrition. Recommendations for fertilizing broccoli vary from one source to the next. You can apply liquid seaweed or compost tea a couple of weeks after transplanting and again a couple of weeks before harvesting, add a compost mulch to suppress weeds and contribute nutrients, or apply a granular fertilizer or liquid fish and seaweed fertilizer when the broccoli heads are forming. Given the varying expert recommendations, you’ll probably need to experiment to see what works best in your garden.

What ongoing care do broccoli plants need?

Weed regularly to reduce competition, especially when the plants are young.

Water regularly – broccoli plants need plenty of moisture, especially when the heads are forming.

Mulch in the summer to keep the soil cool and moist and reduce the risk of premature flowering (bolting).

You may need to provide stakes to support the plants if they will be exposed to high winds.

How big do broccoli plants get?

Broccoli plants usually grow 2-3 feet tall and 1-3 feet wide.

How long does broccoli take to grow?

This depends on the variety. There are some quick-maturing types such as Packman that are ready in around 55 days  and varieties designed to overwinter, such as purple sprouting broccoli, that take 200+ days. However, most varieties will be ready in around 70-120 days from sowing or 45-70 days from transplanting.

When can I harvest broccoli?

You can harvest broccoli at any stage, but it’s best done when the central heads are large enough to be worth using (3-10 inches wide) and additional florets are still in bud. Cut the main head and leave the secondary crop of smaller side shoot florets to ripen, then harvest them as well. If you keep harvesting side shoot florets regularly, the plant should keep producing for some time.

If your plants are grown relatively close together, 5 inches may be the maximum size for the main head, whereas for more widely spaced plants, heads may reach up to around 10 inches in diameter.

Harvest every few days. If the plants are allowed to flower, they’ll stop producing.

Use a knife to harvest the head and subsequent side-shoot florets. You don’t need to keep as much stem with them as with supermarket broccoli – leaving more stem length on the plant will encourage the development of more side shoots.

The broccoli harvest typically lasts for around 2-6 weeks for each plant.  You can keep cutting the side shoots until the newest ones are too small to be worth harvesting.

Can I eat broccoli flowers?

You can eat broccoli once it’s flowered, either picking the flowers off or eating them as well (the broccoli may not taste as good after flowering – some sources say it’s fine, others say the flavour deteriorates). I haven’t tried eating the flowers, but many sources say they’re quite tasty in salads and stir fries.

What’s eating my broccoli plants?

The most likely culprit is the cabbage moth caterpillar (those white moths that are frequent visitors to the garden). These caterpillars, called cabbageworms, might leave holes in the leaves of established plants, but they don’t do any significant damage, whereas seedlings can be killed by these pests. Caterpillars can be removed by hand, and netting can be used to deter adult cabbage moths.

Other creatures that will nibble on broccoli plants include slugs, aphids, flea beetles, cabbage loopers, and the cabbage root fly, and cutworms will chew the stems of young seedlings off at their bases. Many pests can be sprayed off with a blast from the hose or handpicked off in the case of larger pests such as slugs and cabbageworms. Encouraging ladybugs to visit the garden will reduce pest populations, as ladybugs are voracious consumers of aphids. You can also exclude pests with floating row covers or use a homemade natural insecticidal soap. If cutworms are a problem with young seedlings, you can purchase or make protective collars. To make cutworm collars for your seedlings, cut the ends off small yogurt tubs or other similar containers to create 4 inch/10 cm cylinders and place these collars 1 inch/2.5 cm deep into the soil so that they form a wall around each seedling.

Plants growing in less-than-optimum conditions are more vulnerable to infestations, so provide nutritious soil, regular watering, and mulch to maintain soil moisture and keep temperatures cooler. Remove old dead leaves and other debris regularly, as they can harvest pest eggs and disease microbes. Rotate your crops regularly, so that you don’t grow broccoli or other brassicas in the same spot more than once every few years to reduce the risk of disease.

Why are my broccoli plants dying?

If the leaves are turning yellow and wilting, the culprit may be clubroot, a fungal infection that attacks brassicas (this infection can be recognized by the knobby, distorted appearance of the plant roots if you pull the plants up). Remove and destroy any infected plants (do not compost them). The infection can live in the soil for up to 7 years, so it’s important to practice regular crop rotation. You can reduce the risk by adjusting the pH of your soil – the fungus prefers acidic soil, so a pH of 7.5 is a deterrent.

Why do my broccoli leaves have discoloured patches?

Patches on leaves are usually caused by fungal diseases. Common fungal diseases of broccoli include:

Downey mildew, which manifests as yellowish patches on leaves accompanied by white fluffy growth on their undersides, and possibly black spots on the broccoli heads. It’s spread by wind but requires damp spots on leaves to grow.

Powdery mildew, which takes the form of white powdery mould on leaves, most commonly occurs during warm, dry spells, and is also spread by wind.

Ring spot, which is most common in cold, moist weather, causes gray and black spots on leaves, but does not damage broccoli heads, though it can inhibit growth or delay the harvest.

White blister causes white blistered patches on the undersides of broccoli leaves.

To reduce the risk of fungal diseases, rotate your crops each year, water the soil directly to avoid splashing water on the leaves, and remove infected plants and plant debris promptly.

Leaves may also become discoloured due to nutrient or water deficiency.

Why are my broccoli plants producing flowers early?

Broccoli plants will bolt (flower) early due to hot weather and/or dry soil. If you live in climate where summers are hot, grow broccoli only in the spring and fall, choose heat tolerant varieties, and water regularly.

Another cause of early bolting is vernalization, which occurs when transplants are allowed to grow too large before they’re put outdoors. Vernalization is caused by plants thinking they’ve been through a full year of seasons and so it is time to flower. This happens when the plants spend too long in warm indoor conditions and then go out into cooler temperatures. Transplant when stems are less than 1/4 inch in diameter to prevent this problem.

Broccoli plants will also bolt early if there is too much competition, so be sure to weed regularly.

How do I store broccoli, and how long will it keep?

Broccoli will taste best if you eat it on harvest day, but you can keep it for up to a week in a plastic bag in the fridge.

Broccoli can be frozen for longer-term storage. Cut your broccoli into pieces 1.5 inches across or smaller and drop them into boiling water for 2-3 minutes or steam for 5 minutes to blanch. Then chill the broccoli pieces in cold water (otherwise they’ll continue to cook for awhile after removing them from the hot water), drain them, add them to freezer bags (squeezing out any excess air to reduce the risk of freezer burn), and store for anywhere from 6-12 months (sources vary regarding how long frozen broccoli will keep – the majority say that properly stored in the freezer, it should last for 10-12 months).

Can I save my own broccoli seeds?

Yes, but keep in mind that broccoli will cross-pollinate with other brassica species such as kale and cabbage flowering within up to a mile.

Broccoli is a biennial, which means that it flowers and produces seeds in its second year of growth. Wait until the slender seed pods have dried and the seeds inside them have turned to black or dark brown. Save the largest seeds and store them in a cool, dark, dry place. They should keep for 3-5 years in the right storage conditions.

How do I cook broccoli?

For maximum nutritional benefits, cook broccoli as little as possible. Quickly steaming it preserves more nutrients than many of the more intensive cooking methods.

If you’re worried about pests that may be inside your home-grown broccoli, dump the head in a bowl of salted water to soak before preparing it – any bugs or worms will emerge from the head.

For broccoli recipes, see Cooking Light’s Cooking with Broccoli.

Romanesco Broccoli, Image Courtesy of Jon Sullivan, PDPhoto.org
Romanesco Broccoli, Image Courtesy of Jon Sullivan, PDPhoto.org

What’s the difference between regular broccoli, sprouting broccoli, broccoli raab, and broccolini?

When most people think of broccoli, they picture Calabrese broccoli, the large-headed type found in most supermarkets. However, there are a number of different broccoli variants that have been gaining in popularity.

    • Sprouting broccoli is a bushier broccoli plant that develops lots of small heads rather than one large central head. It is started in late summer or early fall, overwintered, and harvested in the early spring, but is otherwise grown in similar conditions to Calabrese broccoli and can be cooked using the same methods. It does best in climates where winters are mild.
    • Broccoli raab, also known as rabe or rapini, is a quick-maturing brassica comprising sharply flavoured shoots and small clusters of buds. It looks and tastes similar to gai-lan (Chinese broccoli) and is closely related to turnips.
    • Broccolini is a hybrid of gai-lan and regular broccoli. It’s more tender and sweet, with small florets on slender, long stalks. It’s cooked in the same ways as regular broccoli, but usually requires less cooking time.
    • Chinese broccoli, also known as gai-lan, has a leafier plant form and a more bitter taste than Calabrese broccoli.
    • Broccoflower, also called Romanesco, looks and tastes more like a large green cauliflower than broccoli, but can be distinguished by its spiky, spiral shapes and patterns.
    • Purple broccoli is a compact purple-floret hybrid (the florets turn green when cooked). It also looks more like a purple cauliflower than Calabrese broccoli, but tastes like regular broccoli.

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References:

    • Berkeley Wellness, (2016). Types of Broccoli. BerkeleyWellness.com.
    • Colorado State University Extension. (2015). Vegetable Gardening in Containers. Ext.Colostate.eduu.
    • Edwards Forkner, L. (2012). The Timber Press Guide to Vegetable Gardening in the Pacific Northwest. Portland, OR: Timber Press.
    • Government of Western Australia, Department of Agriculture and Food. (2015). Diseases of Vegetable Brassicas: Fungal Diseases.
    • Halsall, L. (2012). Small Plot Big Harvest: A Step-by-Step Guide to Growing Fruits & Vegetables in Small Spaces. New York, NY: DK Publishing Special Markets.
    • Herriot, C. (2010). The Zero-Mile Diet: A year-Round Guide to Growing Organic Food. Madeira Park, BC: Harbour Publishing.
    • Jabbour, N. (2012). The Year-Round Vegetable Gardener. North Adams, MA: Storey Publishing.
    • National Center for Home Food Preservation. (2006). Freezing Broccoli.
    • Pleasant, B. (2009). All About Growing Broccoli. Mother Earth News.
    • Moss, W. (2012). Any Size, Anywhere: Edible Gardening. Minneapolis: Cool Springs Press.
    • Tozer, F. (2013). The New Vegetable Growers Handbook. Santa Cruz, CA: Green Man Publishing.