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GroEdibles Blog

Jan 28

Spotlight Edible Of The Day: Cole Crops – Broccoli

Posted by HGEL on 28 Jan 2018. Filed under  Cool Season Crops, Spotlight View Comments

“I do not like broccoli. And I haven’t liked it since I was a little kid and my mother made me eat it. And I’m President of the United States and I’m not going to eat any more broccoli.”
George H. W. Bush


Spotlight Edible of the Day: Broccoli

Besides that presidential dig some years back, broccoli is doing just fine, thank you very much! Consumption of broccoli has shot up in the last couple of decades. A third of American households are eating it at least once every two weeks, up 33 percent since that infamous quote! And since a Georgetown University study in 2011 found that isothiocyanates (ITCs) found in broccoli and other cruciferous vegetables caused cancer cells to die, well, let’s just say broccoli is no longer the awkward kid no one talks to at the party!

FamilyBrassica oleracea var. italica. Cole crops are a group of veggies that belong to the mustard family – Brassicaceae (previously known as Cruciferae). The varieties included in this family are Broccoli (italica), Cauliflower (botrytis), Cabbage (capitat, tuba and sabauda), Brussel Sprouts (gemmifera), Kale and Collards (acephala) and Kohlrabi (gongyloides). Depending on the variety, these cool season crops may be herbaceous annuals, biennials or perennials.

Brassica oleracea var. italica, one of the oldest of the cole crops, originated in Europe and Asia and claim wild cabbage as their ancester. Broccoli comes in two types: sprouting (small shoots) and heading (one large head).
Climatic Requirements – Cole crops are cool weather vegetables, growing best when daytime temperatures are between 65 and 80 F and planted in a (click on image to enlarge)

sunny spot. Temperatures dipping below 40 F will cause harm and possibly early bolting. In many locations, broccoli is grown as a spring and fall crop.
Soil Requirements – HGEL recommends doing a soil test before planting in a new bed and at least once every three years after that. Tests are the only way to really know what steps you need to take to make your soil great. Without one, it’s a stab in the dark and you may waste money adding amendments and fertilizers you may not need.
Although broccoli will grow in a wide variety of soils, a sandy loam is best. All of the cole crops grow well in reasonably fertile, well-drained, moist soils with plenty of added organic matter.  The pH should be between 6.0 and 7.0. A pH in this range will cut down on diseases that plague this crop like clubroot disease and keep nutrients available to plants. A mulch will help with soil temperature and moisture retention.
Cultural Requirements
Planting: Although many of you may have different perspectives on this, it has been my experience that both broccoli and cauliflower do best when set out as transplants rather than planted from seed. A good transplant is 5 to 6 weeks old, sturdy with good color. Older plants or those that have already formed small heads won’t yield as well as younger plants so be selective at the nursery.
Your careful soil prep and correct planting time (not too early) will ensure vigorous growth once plants are planted to prevent the flowering heads of broccoli from “buttoning”. “Buttons” are small, unusable heads on small plants stunted by insufficient or inconsistent watering practices, weeds, or insects. A few days of low temperature (35oF to 50o F) can also cause buttons to develop. Choose your planting time carefully!
If you’re planting from seed, sow seeds 1/4 inch deep space rows 24 to 36 inches apart, setting transplants or thinning seedlings 18 inches apart. In the case of cole crops, proper spacing is important for maximum crop yield.
Fertilizing: Having done a soil test before planting and adding lots of good compost, your soil should be adequately fertile come planting time. One thing to keep in mind is that Broccoli (and cole crops in general) are heavy nitrogen feeders. Nitrogen is the most mobile of the macro nutrients and is taken up quickly by heavy N feeding plants like broccoli. Synthetic N can leach out of soil very fast through irrigation and run off. HGEL ALWAYS recommends avoiding synthetic fertilizers, using only organic materials that will provide the nutrients you need to replace/replenish.
Here’s a great guide from the University of Georgia: “How to Convert an Inorganic Fertilizer Recommendation to an Organic One” – .  Scroll down to Table 1. Guide to the Mineral Nutrient Value of Organic Fertilizers which shows you what nutrients the listed fertilizer will replace and how fast.
I stress that just by adding organic matter such as well-rotted manure or compost to the soil you will increase the level of nutrients, improve soil microbial activity, and increase water-holding and nutrient-holding capacity hence making your soil more fertile naturally. Organic matter also improves the physical condition or texture of the soil for cultivation and improves soil structure so the surface of the soil does not crust. Any soil can be/should be improved through the addition of organic matter. As HGEL has often advised, cover crops are also an important, inexpensive way to add organic matter to the soil, and much of plants N needs can be met via cover cropping.
Crop Rotation: Crop rotation is an important cultural practice for cole crops to avoid disease problems. Rotate crops by alternating the location of plantings with a different crop each year. Try to avoid planting plants from the same family in the same place for at least two seasons…three is better. Here is a great resource from Iowa State on crop rotation:
Irrigation: Cole crops do require regular watering which is especially important if your soil texture tends toward the sandy side. Remember though that over-watering can lead to many problems like disease and even attract pests. HGEL always prefers a drip or micro-spray system as this cuts down water splashing and excessive leaf wetting which helps to avoid water transmitted fungal diseases like powdery mildew and blight. It also conserves water.

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Weed Control and Mulching: Use shallow cultivation for weed control. Deep cultivation close to the plants will damage the root systems and reduce yield and quality. During the growing season, control weeds by mulching and hand-pulling. These strategies are the best means of control in a small planting. During the winter and spring months, periodically check the planting for the development of winter weeds that should be removed. Many organic growers apply natural mulches such as straw, leaves or compost around the plants, after they become established, to control weeds. This practice is well-worth the labor as it conserves soil moisture, attracts earthworms and eventually enriches the growing area with organic matter and nutrients.

Organic Pest/Disease Control –

Here is a link to UC Davis IPM site about some common pests and diseases of cole crops:

Pest Management Pests/Insects: Pest problems will vary depending on where you’re gardening.

Flea beetles and root maggots can cause serious damage to cole crops, chewing away the roots of young seedlings so they wilt and die. Covering beds or rows with floating row covers of spun-bonded polyester for the first month of more of growth will prevent attacks by both these pests.
The larval stages of several different species of moths can also cause serious damage. Row covers left on throughout the growing season, or regular applications of Bt (Bacillus thuriengiensis), an organic bacterial poison that kills only caterpillars, will control cabbage worms of all species.
Disease Management: To control fungal and soilborne bacterial diseases, rotate your planting site (see above) and irrigate correctly.
Some common diseases…
Downy mildew caused by Peronospora parasitica is the major fungal disease in broccoli. University research has shown that foliage can suffer a substantial amount of mildew lesions without affecting yield or quality. Mildew-tolerant varieties are available.
Black rot (Xanthomonas campestris pv. campestris) occurs occasionally in Imperial County. It is usually introduced to a farm through infected seed or transplants. Field conditions are not usually conducive for development of this disease in the desert. Use disease-free planting material.
Cladosporium sp. are often surface contaminants on broccoli heads especially during rainy periods or when there is heavy morning dew.
Clubroot is a soil-borne disease causing stunted plants which wilt even in moist soil. Raise the pH to 7.0 to 7.2 if this disease is a problem. AGAIN – practice rotation!
In an organic system pest and disease management is based on prevention. The goal is to have a healthy, balanced plant and soil system in which pest populations will be stay within tolerable limits. In a conventional system, synthetic pesticides may help a grower save the current crop from an immediate pest problem; however, in many cases, the problem recurs or another develops AND the cumulative effect of using synthetic fertilizers or pesticides is damaging to the environment, humans and animals. The organic approach is based on the theory that major pest problems usually occur when something is out of balance in the system. These are questions organic gardeners should ask themselves when things seem to be going wrong:

  • Are the plants undernourished or stressed from growing too quickly?
  • Is there a nutrient imbalance?
  • Is the soil too wet or too dry?
  • Has a good crop rotation been followed?
  • Is there a diversity of plants to support beneficial insects?

Studying the problem and trying to determine why it occurred should help prevent similar problems in the future. This will, of course, take time to learn and develop.
A Word about the Integrated Pest Management (IPM) approach
This is system is well-suited for organic production and one, as a Master Gardener, I always recommend. IPM is a system in which insects, diseases, and weeds are closely monitored, and different methods are used to keep pest populations at levels that are not economically damaging with minimal adverse environmental effects. IPM encompasses use of cultural and biological control methods, use of resistant varieties, and a VERY judicious use of pesticides. HGEL recommends that, In the event pesticides must be used, select ORGANIC ones with low toxicity, non-persistent residues, narrow spectrum of control, and low environmental impact.
A Resource Guide for Organic Pest and Disease Management (Cornell Univ.)
There are four regional IPM centers in the U.S. – North Central, Northeastern, Southern and Western. Here is a link to a searchable database to find the IPM sites in your region:
There is no guarantee that once an organic system is established there will never be a disease, weed, or insect problem. Stressful conditions that a gardener cannot control will occur, such as weeks of endless rains, droughts, periods of extremely high temperatures, hurricanes, plagues of grasshoppers, or hail. Likewise, if an airborne disease invades your area, your plants will probably be infected. However, with careful observation and preparation, an organic system should progressively have fewer pest problems as years go by.
Harvest/Storage Harvest:
Broccoli heads are removed by hand by snapping the stem. Broccoli requires rapid cooling to insure preservation of quality. Harvested heads should be taken to the cooler immediately.
“If bunched broccoli is stored at 32°F with a relative humidity of 90-95 percent, it should have a 10-14 day shelf life. At higher temperatures the shelf life will decrease drastically. Storage at 50°F, for example, will reduce the shelf life to 5 days. Excessive storage time will cause yellowing and softening of the tissue and beads. Off-flavor and bad odor may also develop.Broccoli should never be stored with ethylene sources such as ripening melons, avocados, bananas, apples, or pears. Exposure to ethylene will accelerate the yellowing of beads.” Keith S. Mayberry, Farm Advisor, U.C. Cooperative Extension, Imperial County.

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