Broccoli and Cauliflower
- Plant family: Brassicaceae or Cruciferae (Mustard, Crucifers, Cabbage)
- Season: Cool
- Life Cycle: Biennial, but grown as an Annual
- Seed to first harvest: 75-90 days
Broccoli and cauliflower are herbaceous plants (meaning they have non-woody stems) and are widely adapted throughout temperate and subtropical regions of the world. They are closely related members of the Brassicaceae family, also known as the cabbage family, which includes other cool season cole crops like cabbage, Brussels sprouts, kale, kohlrabi, collards, and radish (see Figure 1). Cole crops can tolerate frost, are generally hardy, and mature in cool weather. The name broccoli comes from the Italian word “brocco” meaning “shoot” (which refers to sprouting broccoli), while the name cauliflower is believed to have been derived from the Italian word “cavolfiore,” meaning “cabbage flower,” and is the heading version of a very similar crop.
The Romans grew sprouting broccoli in the 1st century in areas around the Mediterranean Sea. It is believed that heading broccoli was derived from leafy cole crops during the 6th century in the northern Mediterranean region. Around 1720, broccoli was introduced to England and then to the U.S. in the early 1800s by an immigrant from southern Europe. It wasn’t until the early 1900s that broccoli became popular in the U.S. Today, the U.S. is the largest world producer of broccoli (see Figure 2).
Cauliflower likely originated in the eastern Mediterranean region from a genetic mutation of wild leafy cabbage, resulting in a heading flower-like growth (cauliflower) rather than a single bud (cabbage). The earliest records of this crop date to the 6th century B.C. There is documentation that cauliflower was grown in Turkey and Egypt during the 16th century before being introduced to England and France in the 17th century. As with broccoli, cauliflower was likely brought to the U.S. in the early 1800s, with popularity rising in the 1900s. Heat-tolerant forms of cauliflower have been developed in India over the past 200 years using European varieties (see Figure 2).
Most types of broccoli tend to be annuals (one life cycle/year) that do not require a cold period (vernalization) for head formation or flowering. The part that is consumed is a flower structure (inflorescence) with many closely spaced flower buds clustered in a head. The tender portion of the stem is also eaten.
Cauliflower may be either annual or biennial (the plant’s life cycle from seed to flower takes one or two years, respectively) based on variety, but is most commonly grown as an annual crop. The white, flowering head of a cauliflower is botanically an undifferentiated flower along with stem tissue and is referred to as a curd.
Broccoli and cauliflower are cool season crops that are also fairly heat and cold tolerant. The broccoli head or cauliflower curd are the parts harvested and are typically green for broccoli and white for cauliflower, although other color variations exist (see Figure 3). Broccoli raab (or rapini, B. rapa), is an early maturing Brassica crop that is related to turnip and produces tender leaves, shoots, and small florets in much smaller heads (see Figure 3).
Broccoli is considered the easier to grow of the two crops, and after the main head is harvested, it produces side shoots for extended production. Broccoli is also more heat tolerant and can be grown in subtropical climates. Most varieties of broccoli are grouped into three maturity types: early, medium, or late. Be sure to select varieties for the growing season when the crop will be produced. Fall and winter plantings (September to January) have the potential to be damaged by hard freezes. In general, for an early spring crop select early and mid-season varieties; for a fall crop use mid- or late season varieties. Broccoli varieties differ in disease resistance, days to maturity, and weather tolerance; most varieties are green, domed, and similar in size.
Most cauliflower varieties produce white, domed curds that are similar in size and do not produce side shoots. In general, cauliflower is more susceptible to weather extremes, and may require additional maintenance to blanch curds a white color. However, there are also some colorful varieties recommended for Louisiana that don’t require blanching: Cheddar (orange curd), Graffiti (purple curd), and Veronica Romanesco (green, pointed, spiral curd).
Broccoli and cauliflower have either open-pollinated (including heirloom) or hybrid varieties. There are two recommended heirloom varieties for Louisiana: Calabrese and De Cicco Italian broccoli. These seeds have been saved for at least 50 years, can be saved each season and replanted, and are open-pollinated.
Brassica crops have perfect, self-pollinating flowers (containing both male and female parts) but easily cross-pollinate with other Brassicas. If saving seed, different varieties of Brassicas must be separated by a distance of 1/8-1/2 mile to avoid cross-pollination. Generally, it is not recommended to save seed for future planting with hybrid varieties as they are usually not expressed properly in the next generation.
It is important to select varieties based on recommendations in Table 1 as these have been tested for suitability for Louisiana.
When and How to Plant
It is recommended to start seeds inside for both crops approximately 5-7 weeks before the recommended planting dates (refer to the Broccoli and Cauliflower Planting Guide, Table 2). Using seed germination trays (with at least 1.5-inch diameter cells), plant one seed per cell (unless the germination rate is low or conditions are less than ideal; then plant 2 seeds per cell) at a shallow depth (1/8-1/4 inch), just deep enough to be covered with a thin layer of soilless potting mix. Make sure to keep the seed trays in a warm (optimum germination temperature is 85 degrees F), well-lit area and keep soil moist, which usually requires daily light watering. A seedling heat mat and plastic dome lid are helpful in maintaining ideal germination conditions. If multiple seeds were planted per cell, thin seedlings to one plant per cell after a few true leaves develop. Broccoli and cauliflower are generally transplant hardy and can be planted outside once 4-5 true leaves develop, if soil temperature is between 65-75 degrees F (minimum 50 degrees F). The use of a soil temperature map can help guide planting decisions. A few days before planting transplants outside, it is recommended to follow a hardening-off process to transition seedlings to outdoor conditions.
Refer to the Broccoli and Cauliflower Planting Guide (Table 2) when transplanting seedlings outside. Planting broccoli plants closer together will result in smaller heads, about 3-4 inches in diameter, while planting farther apart will produce larger heads, about 8-12 inches in diameter.
Both broccoli and cauliflower are cool-season, frost-tolerant crops preferring cool days between 55-75 degrees F and cold nights between 40-55 F, but are tolerant to heat and cold, depending on the variety. Optimal broccoli head development occurs between 54-68 degrees F. Above 77 degrees F, compact heads may not form and bolting may occur. Low temperatures during early plant development can cause premature heading, and growth is slow at temperatures below 41 degrees F. Broccoli heads are cold hardy to as low as 20 degrees F for short periods if properly hardened, while cauliflower is sensitive to near-freezing temperatures. In general, for both broccoli and cauliflower, young seedlings are less freeze tolerant than mature plants. For cauliflower, warm temperatures tend to inhibit or delay curd formation while promoting vegetative growth. Cooler temperatures favor curd formation, with best curd quality at 61-64 degrees F. Above 68 degrees F, curd quality decreases for many varieties. Curd development in some tropical cauliflower cultivars can continue up to 86 degrees F, though premature curd formation can sometimes be a problem. For the best chance of success, plant in the fall and select early-maturing varieties.
Table 2. BROCCOLI AND CAULIFLOWER PLANTING GUIDE
|Category||Transplant Outside Dates||Spacing (inches)||Days to Harvest*|
|Broccoli||North LA: Feb-March 15; Aug-Oct
South LA: Jan 15-March 15; Aug-Oct
|10-24”||2 rows per bed, 12-24” apart||24-36"||75-100 days|
|Cauliflower||North LA: Feb-March 15; July 15-Oct
South LA: Jan 15-Feb 15; July-Oct 15
|18-24”||1 row per bed||24-36"||75-90 days|
*Days from seed to harvest; days in parentheses are transplant to harvest
Note: Table adapted from LSU AgCenter and UF Extension Planting Guides, and Southeastern U.S. Vegetable Production Handbook
Where to Plant
Broccoli and cauliflower should be planted in deep, well-drained, fertilized soil with a soil pH of 6.0 to 7.5. These crops are less tolerant of acidic soil, so pH should be above 6.0. It is important to select a planting area in full sun (at least 6 hours/day) and preferably plant these crops in a sandy loam soil high in organic matter. It is recommended to plant broccoli and cauliflower in box beds or traditional raised garden rows that are about 12 inches tall to ensure good drainage. In all types of gardens, it is recommended to add a layer of compost, peat moss, rotted hay, or other organic matter and mix into the soil to optimize plant health.
Reflective plastic mulch — or a plastic fabric/film — is recommended to deter aphids that transmit viruses, to increase soil temperature, and to control weeds. Drip irrigation is also recommended when using plastic mulch to maintain ideal soil moisture and encourage productive plants.
It is recommended to rotate plant families — avoid planting vegetables from the same plant family in the same area of the garden — to reduce disease and pests. It is recommended to rotate Brassicaceae crops on a longer, 4-year cycle, and if possible, rotate every year. Floating row covers may be used to keep flea beetles, root maggots, and other insects from feeding on young transplants.
Both crops have a relatively high water demand; be sure to keep soil moist and use mulch to aid in moisture retention. Provide adequate water after planting and during heading. Cauliflower is very sensitive to drought and water stress and this could result in failure to develop a curd. Generally, these crops require 1-2 inches of rain or supplemental irrigation weekly.
Broccoli and cauliflower are considered heavy feeders and will benefit from the addition of organic matter to the soil. Cole crops especially benefit from soil testing for micronutrients, as they suffer from several nutrient deficiency disorders. Growing at a pH below 6 makes molybdenum unavailable for uptake and causes browning of leaf edges. Liming with dolomitic limestone should be done to raise pH, if recommended, following soil test recommendations. Adding sodium molybdate may also help. Dolomitic limestone consists of calcium and magnesium and corrects magnesium deficiency, which often appears as interveinal chlorosis in cauliflower on low pH soils. Boron deficiency causes hollow stem, another common disorder, requiring the addition of boron to soil.
Organic fertilizers such as compost, fish emulsion, composted poultry litter or manure, worm castings, and blood or bone meal originate from living organisms. They are far more environmentally sustainable and safe than traditional synthetic fertilizers. They naturally release nutrients more slowly and over a longer period of time. When applying organic fertilizer, it is important to use in unison with compost, cover crops, and crop rotation, which all work together to build soil health. Learn how to convert inorganic fertilizer recommendations to organic fertilizers here.
Alternatively, a synthetic fertilizer may be used at the rate of about 1.25 pounds (2.5 cups) of 13-13-13 for every 25 feet of row or 75 square feet. Broadcast or sprinkle evenly over the soil and then mix in about 3-6 inches deep using a rake. Supplemental sidedressing, or reapplication of synthetic fertilizer, is recommended after 3-4 weeks and again 2-3 weeks later. Sprinkle a small amount around each plant, keeping it several inches away from the plant stem; water into the soil. Because of their slow, steady release of nitrogen, crops fertilized with organic fertilizer do not usually need to be sidedressed, but fish emulsion can provide a quick release form of nitrogen for sidedressing heavy feeders like broccoli and cauliflower.
Sunlight exposure to the heads of white cauliflower varieties causes them to turn light purple or yellow. Blanching is a technique that results in creamy-white heads. A simple method to blanch the head is to gather the outer leaves, pull them over the heads, and secure them together with a rubber band, twine, or clothespins. Another method is to crack the midribs of the leaves and fold them over, completely covering the head. Begin blanching when the developing heads are just visible through the leaves, about 1-2 inches in diameter. Blanching is not actually necessary for cauliflower production, and this technique may cause increased humidity levels and susceptibility to diseases. Colored cauliflower varieties don’t require blanching, but instead require light exposure for proper color development.
Plastic mulch will control most of the weeds; hand-pull weeds close to the plant, especially in the planting holes. Weed pressure may be lowered with crop rotation and timely cultivation or weeding early in the growing season.
Insect Pests and Diseases
Common insect pests for broccoli and cauliflower include aphids, caterpillars, and whiteflies. It is recommended to cover transplants with row cover to reduce pest pressure. Broccoli and cauliflower are susceptible to some foliar and fungal diseases (e.g., anthracnose, leaf spot, root rot, Fusarium yellows or wilt, powdery and downy mildew), bacterial diseases (black rot, head rot), and physiological disorders (tipburn). There are a number of other physiological disorders possible with cauliflower, such as “buttoning” (small curd development), if temperatures are between 35-50 degrees F for more than 10 continuous days, so take care to transplant during the recommended planting dates (Table 2). “Riceyness,” or a velvet-like curd surface, is caused by cold temperatures followed by warm temperatures. “Blindness,” or no head formation, is caused by low temperature damage when the plant is young and tender. Generally recommended tools for disease prevention include using mulch; avoiding overhead irrigation; adequate plant spacing; crop rotation; and weed control. See Table 3 to aid in diagnosis and management of some common broccoli and cauliflower insect pests and diseases.
Table 3. Organic and Natural Management for Common Insect Pests and Diseases of Broccoli and Cauliflower
|Symptoms||Diagnosis||Organic and Natural Pest Management|
|• Warm, humid conditions
• Circular, water-soaked spots on foliage
• Stunted seedlings
• Plant death
|Alternaria leaf spot|
|• Curled and yellowed leaves
• Stunted crops
• Sticky honeydew on leaves
|• Bacteria causes black veins and stem
• Leaves with yellow margins
• Leaf drop
|• Late spring occurrence
• Light green larvae with faint yellow stripes
• Holes in leaves and partially eaten
|Caterpillars (cabbage worm, cabbage looper)||
|• Stunted plant roots and top growth
• Roots unable to absorb water and nutrients
|• Yellow splotches on leaves
• White downy growth on lower surfaces
• Damp, cool conditions
• Damping off
|• Yellowing in lower leaves after transplanting
• Wilted leaves, defoliation
• Stunting and plant death
• Warm weather
|Fusarium yellows or wilt||
|• Bacterial rot in almost mature heads
• Yellowing of individual flower buds
• Dark brown sunken lesions
• Leads to soft rot causing mushy heads and foul odor
• Leaf discoloration
• High moisture and high temperature
|• Soil deficient in boron
• Plant spacing too wide
• Curled leaves, deformed foliage
• Brown curds or heads
• Hollow stem centers
|• Fungus found in waterlogged, compacted soil
• Wet soil at plant base
• Purple discoloration in older leaves
• Purple stem canker
• Late summer, early fall
• Stunted plants; off-color
• Plant wilt and death
|Phytophthora root rot||
|• Small, round white spots with fungal growth on older leaves with dark, mottled underside
• Leaves covered with talc-like powder; leaf yellows and dies
• Hot, dry conditions
|• Edges of leaves turn brown or speckle||Tipburn||
|• Leaf discoloration and wilt
• Tiny white flies flutter when plants are disturbed
• Sticky honeydew on leaves
• Black, sooty mold fungus
Note: Table adapted from Texas A&M AgriLife Extension; Alabama A&M and Auburn Universities Extension; and UMass Extension Vegetable Program. The Louisiana Pesticide Law regulates the use of pesticides in schools to protect children and staff from harmful exposure to chemicals and is enforced by LDAF. The recommended alternative to routine pesticide use is Integrated Pest Management (IPM), which combines pest control, disease management techniques and organic/natural alternatives, many of which are found in this table.
Harvest and Storage
Broccoli is harvested when the heads are about 7 inches tall from crown to base and the flower buds are still tight, but a few have begun to loosen. Be sure to harvest before many flower buds start opening, flower head begins to turn yellow, or the stem becomes woody. Cut the broccoli head with a sharp harvest knife leaving about 6 inches of stem. This will allow for additional harvests of side shoots (usually 2-3 more times). The broccoli head is the main part consumed, but stems and leaves are edible as well as flower stalks and flowers.
For white varieties of cauliflower, harvest when the heads have turned pure white from blanching. For all varieties of cauliflower, harvest before the curds become loose and ricey. Cut center heads using a sharp harvest knife about 1 inch down the stem (see Figure 5).
After harvest, the crop needs to be cooled down to remove field heat and placed in a refrigerator or cooler where there is high humidity. Removing field heat will avoid moisture loss and wilting and preserve quality and shelf life. At an ideal storage temperature of 32 degrees F with high humidity (95-100%), broccoli will last approximately 10-14 days and cauliflower 3-4 weeks.
Broccoli and cauliflower can be preserved by freezing after washing, either raw or cooked.
Broccoli and Cauliflower are Nutritious and Good for You
Very high in Vitamin A
Important for eye health, a strong immune system, and cell growth
High in Potassium
Essential for body function, especially the heart, kidney, nerves, bones, and muscles
Rich in Vitamin C, B2, and B6
Important for bones, skin, blood vessels; converts food into energy; supports immune system and brain health
Provides calcium, iron, and magnesium
Bone health; produces red blood cells; important in muscle and nerve function
Good source of dietary fiber
Important for bowel health, lowering cholesterol, controlling blood sugar, and maintaining a healthy weight
Louisiana Harvest of the Month: Roasted Broccoli
Taste-testing ideas: broccoli and cauliflower omelet, broccoli or cauliflower soup, vegetable pasta salad, Asian stir fry or fried rice, roasted broccoli and cauliflower, cauliflower rice, mac n’ cheese with broccoli, chicken and broccoli bake, broccoli salad, cauliflower tots
Other websites with many broccoli and cauliflower recipes:
- Southeastern Vegetable Extension Workers, 2020 Southeastern U.S. Vegetable Crop Handbook
- LSU AgCenter, Louisiana Commercial Vegetable Production Recommendations
- LSU AgCenter, Louisiana Vegetable Planting Guide
- LSU AgCenter, Vegetable Gardening Tips: Cole Crops
- UF Extension Planting Guide
- Vegetable Production Handbook of Florida
- Texas A&M AgriLife Extension, Vegetable Varieties for Central Texas
- Texas A&M AgriLife Extension, Easy Gardening: Cole Crops
- Texas A&M AgriLife Extension, Commercial Crop Guides: Broccoli
- Texas A&M AgriLife Extension, Commercial Crop Guides: Cauliflower
- Swiader, John M & Ware, George W (2002). Producing Vegetable Crops (5th edition). Interstate Publishers, Inc.
- Maynard, Donald N & Hochmuth, George J (2007). Knott’s Handbook for Vegetable Growers (5th edition). John Wiley & Sons, Inc.
- Decoteau, Dennis R (2000). Vegetable Crops. Prentice-Hall, Inc.
- Sukprakarn, S, Juntakool, S, Huang, R, and Kalb, T (2005). Saving your own vegetable seeds—a guide for farmers. AVRDC publication number 05-647. AVRDC—The World Vegetable Center, Shanhua, Taiwan. 25 pp.
- Alabama A&M & Auburn Universities Extension, Crop Production
- UMass Extension Vegetable Program: Disease, Insect, and Mites Fact Sheets
- Purdue Extension FoodLink: Broccoli
- Purdue Extension FoodLink: Cauliflower
- Seed Savers Exchange, Seed Saving: A Guide to Isolation Distances
- University of Georgia Extension, How to Convert an Inorganic Fertilizer Recommendation to an Organic One, Circular 853
- Michigan State University Cooperative Extension Service, Disorders of Cole Crops