Broccoli

BROCCOLI
Brassica oleracea var. italica

FAMILY CHARACTERISTICS
    Many plants in the Brassicaceae family are important vegetables worldwide. Plants from the Brassicaceae family are mostly native to Europe, the Middle East, and Asia. All are similar in their cultural requirements and taxonomic relationships. The Brassicaceae family was formerly called Cruciferaceae. There are about 350 genera and 3,000 species in the Brassicaceae and many occur in the north temperate zone. All are hardy, cool season crops that are susceptible to the same insects and diseases. These plants are annuals, biennials, or perennial herbs with a pungent or acrid watery juice.
    All of the cole crops can be crossed and many of the flowers cannot be fertilized by their own pollen. Being self incompatible makes it easy to make hybrid selections. Their leaves are simple and alternate without any stipules.   The inflorescence is in terminal racemes or corymbs, and the flowers are often perfect with four sepals and petals.
    The family includes many vegetables: broccoli, cauliflower, cabbage, brussel sprouts, collards, kale and kohlrabi. There are also some oilseeds, such as oilseed rape. Nasturtiums, an ornamental, is also found in the Brassicaceaes. Many of the members of the family are found in the wild.
Family members include:
        Armoracia rusticana Gaertn., Mey., Scherb.; Horseradish
        Barbarea vema (Mill.) Aschers; Upland Cress
        Brassica carinata A. Br.; Abyssinian Mustard
        Brassica campestris L. (Chinese group); Pak-Choi, Chinese Mustard, Celery Mustard
        Brassica campestris L. (Pekinensis group); Pe Tsai, Chinese Cabbage, Celery Cabbage
        Brassica campestris L. (Perviridis group); Spinach Mustard, Tendergreen Mustard
        Brassica campestris L. (Rapifera group); Turnip
        Brassica campestris L. (Ruvo group); Broccoli Raab, Rapa, Italian Turnip
        Brassica juncea (L.) Czern. & Coss.; Leaf, Brown and Indian Mustard
        Brassica napus L. (Napobrassica group); Rutabaga, Swede, Swede Turnip
        Brassica napus L. (Pabularia group); Siberian Kale, Hanover Salad
        Brassica nigra Koch.; Black Mustard
        Brassica oleracea var. acephala D.C.; Collards, Scotch Kale
        Brassica oleracea var . botrytis L .; Cauliflower
        Brassica oleracea var. capitata L.; Cabbage
        Brassica oleracea var. fruticoca Metz.; Thousand-headed Kale
        Brassica oleracea var. gemmifera, D.C.; Brussel Sprouts
        Brassica oleracea var. gongylodes L.; Kohlrabi
        Brassica oleracea var. italica Plenck.; Broccoli
        Crambe maritima L.; Sea Kale
        Eruca sativa Mill.; Roquette or Rocket Cross
        Lepidium meyenni Walp.; Maca
        Lepidium sativum L.; Land Cress, Pepper Grass
        Raphanus caudatus L.; Rat-tail Radish
        Raphanus sativus L.; Radish
        Raphanus sativus L. (Longipinnatus group); Daikon or Chinese Radish
        Rorippa nasturtium-aquatkum (L. ) Hayek; Water Cress

CROP HISTORY AND DEVELOPMENT
    Broccoli is believed to be the first of the cole crops to evolve from the wild species of kale or cabbage and was cultivated by the Romans. It was introduced in England in the early 16th century known as “ Italian asparagus” or “sprout cauliflower”. In 1775, John Randolph described broccoli as ‘the heads like cauliflower’ and ‘the stems will eat like asparagus’. Broccoli is a relatively recent introduction into the United States. It was grown in the 1800’s, but was not popular until later. The first shipment from the west to the east was in 1923 and was really only found in Italian areas of the country. Broccoli means ‘little sprouts’ in Italian. It became an important vegetable in the US during the 1930’s.
    There has been a lot of breeding work done in broccoli to improve the adaptability to growing areas, improving quality, and increasing disease resistance. Cultivars can now be labeled spring, summer or winter based on their cold and heat tolerances. The varieties can also be classified as early, midseason, and late. The ideal broccoli plant is high yielding that can be mechanically harvested in a one time harvest.
    Common Cultivars There are two types of broccoli, the sprouting, which is in the group Italica and considered an annual, and the heading type which is a strong biennial.
For 1998-99 commercial broccoli production the following cultivars were recommended.
    'Green Duke'- 50 days to maturity after transplanted, does well in spring and fall.
    'Sultan'- 60 days, excellent fall crop; single large heads; tolerates early fall heat
    'Green Charger'- 64 days, good fall crop; single large heads
    'Pinnacle'- 64 days, fall crop, small bead size, good for bunching, downy mildew tolerant.
    'Ninja'- 86 days, spring or fall
    'Arcadia' - 86 days, spring or fall
    'Emperor'- 65 days, Uniform; good side shoots; spring or fall; high yielding; close spacing
    'Green belt'- 67 days, fall crop; large head; shorter stalk; slow maturing; small bead size, good for bunching.
    Most of the broccoli found are F1 hybrids, some other cultivars include, 'Packman', 'Regal', 'Saga', 'Genji', 'Green Valiant', 'San Miguel', and 'Marathon'.
    Specialty types. There are also some heirloom types that are good for traditional old fashioned varieties such as the 'Green Sprouting Calabrese'. The Romanesco broccoli is Italian with a nut like texture for salads and dips. 'Minaret' is a good variety for this specialty type. 'Broccoli Raab' is a traditional Italian specialty that combines the qualities of mustard greens and broccoli for salads and light cooking. ‘Sessantina Grossa’ and ‘Spring Raab’ are two good varieties. Recently crosses between the broccoli and cauliflower have been made since they are highly cross pollinated and are called brocco-flower.
    Production Locations In 1997, a total value of $495,515,000 in broccoli production was obtained in the United States. In 1997 a total of 134,200 acres were harvested in the US with a total yield of 17,315,000 cwt. The average yield was 129 cwt. an acre. Fresh market and processed broccoli was up 12% from 1996. California produces the most of the US commercial broccoli crop.   Arizona and Texas also produce, but their amounts do not come close to California production.   In 1996 broccoli grower prices were and average of $35/cwt in winter months and averaged $23 in fall, and $27 in summer.   The US imports fresh and frozen broccoli from Mexico and Canada but also from around the world. In 1996 about 400,000,000 lbs of frozen broccoli, and about $6,500,000 of fresh were imported into the US. The United States imports and exports. They export almost as much as they import.

PLANT CHARACTERISTICS
    Overview. The edible part of the broccoli plant is a tender stem and unopened flower buds. They are a good source of Vitamin A, calcium, and riboflavin or B2. Broccoli and cauliflower are quite similar morphologically, but the broccoli produces a green head with longer and more slender floret stalks than cauliflower.   After the main stem has been harvested, the axillary buds that are lower on the main stem are induced to develop into smaller heads, which can also be harvested in home gardens. They are not harvested in commercial production.
Ideal for harvest

    Root System. The seedling will generally produce a red colored hypocotyl, two notched cotyledons and a tap root with lateral roots. Usually during transplanting the tap root is damaged and therefore many adventitious roots will arise. Most of the roots are 0.5 mm with few reaching 1 cm thick. In the beginning the roots are quite shallow and the lateral roots are growing horizontally. The roots can be found up to 3 feet away from the plant. After a few months of growing some of the roots will mine vertically to a depth of 1.5-2 m. The majority of the roots occur in the top 20-30 cm. The root system that develops is influenced greatly by water and cultivation.
   Stem. The stem is waxy, usually unbranched and, from it arise the leaves and flower heads.
   Leaves. The leaves are simple, alternate and without stipules. Many times they are pinnately lobed.
   Flower. Branched flower clusters form on 2-2 ½ ft tall plants. The flowers are bright yellow. There are four sepals, six stamens, two carpal and four petals. Broccoli flowers have a superior ovary. The buds are dark green and tightly packed on top of the plant. Broccoli exposed to 40°F will initiate flower primordia much quicker than plants grown in higher temperatures. The flowers are pollinated mostly by bees.

Flower Development Seed. The fruit of broccoli is a glabrous silique. There are between 10-30 seed per silique. About 325 seed will constitute a gram, and approximately 9,000 seeds make up an ounce. It will take about 144,000 broccoli seed to make up a pound. The seed should be planted ½ inches deep. It will take the seed about 10 days to germinate.

Seed Development
PROPAGATION METHODS
Temperatures. Broccoli is a cool season crop. It can be grown as a spring or fall crop, but it is susceptible to cold injury especially when the plants are small and tender. The optimum time for planting is with day temperature between 60-70°F and night temperatures between 50-60°F. Temperatures below 32°F for periods of 36 hours have killed broccoli plants. And extended periods in the 30’s have stunted the plants.

Transplants. Using transplants gives a greater control over the quality and timing than if they are direct seeded in the bed. The soil should be a light artificial potting media. Sow the seeds directly into the cell and thin when there are two leaves on each plant. While in the greenhouse the young plants should be watered two times a day and fertilized every two weeks with a soluble fertilizer. The transplants should be placed in beds 8-10 inches high with 2 rows per bed. The rows should be 36-42 inches apart. If planted 10 inches apart there will be 21,000 plants per acre and 15 inches apart there will be 14,000 plants per acre. Exposure of transplants to low temperatures may cause premature bolting. It will usually take about 5 weeks to produce transplants in the greenhouse that can be set out in the field.

Growing transplants

Direct Seeding. Direct seeding is used primarily for fall crops. A recommended 1-1 ½ pounds per acre is needed. There should be 12-24 inches in between each plant after thinning and there should be 18-36 inches between each row. Direct seeding is more risky because the soil may crust and inhibit seed emergence. For direct seeding it is important to have light friable soil. Plants produced in the cool fall weather are slow growing and usually produce higher quality (tighter) heads.

Crop scheduling. For spring crops grown in the southern states (Ga, N.C., S.C. Al.) the seeds should be sowed in the greenhouse between January and March depending on the region and set in the field from March to April. For fall direct seeding it would be beneficial to sow seeds in mid July to September.
These times are very general and it really depends on which region you are in as to when you should plant. There is much difference in the mountains, piedmont and coastal plains of these states and proper planting time should be in tune with your specific environmental conditions.

Broccoli field

CULTURAL PRACTICES
    Overview. Broccoli requires cool temperatures, irrigation, weed control, and disease and insect management for maximum production.
    Soils. The soil for broccoli must be fertile, well drained and high in organic matter. The optimum pH is between 5.7-6.5. Lime should be applied as needed according to soil tests. It is important to keep your pH levels at optimum because above or below could increase the susceptibility of the plant to disease and insects.
    Fertility. A soil test should be taken before the plants are placed in the soil. Fertility is similar in all the cole crops, but broccoli requires more boron for normal growth. To do a plant analysis in the field, collect about 12 mature leaves that are new growth. Solubor is a good source of boron to add to the soil. A ton of broccoli will remove 10 pounds of N, 3 pounds of P₂0₅ and 8 pounds of K₂0. If boron is deficient it can cause blackened hollow stem.
Plant ready to form head

Potassium deficiency

Hollow heart - Boron deficiency

    Weed Control. It is important to control weeds during broccoli production. The cultivation should be shallow as to not disturb the root system. Herbicide recommendations can be found through the local extension service.
    Irrigation. Broccoli is a fast growing succulent plant that requires even soil moisture. Uneven soil moistures will create adverse affects on the broccoli growth. Irrigation is necessary if natural rainfall does not suffice; 1 to 1 ½ inches of water a week is generally an irrigation requirement.

INSECTS
    All crops are susceptible to some kind of insect damage. Many of the insects that damage broccoli damage other cole crops as well. Integrated pest management is an effective way to regulate the insect populations in the field. Using resistant cultivars is an important tactic in trying to combat pests.
    Aphids (Brevicorne brassicae) are usually a problem on broccoli because they lodge within the dense buds, and suck sap from the young leaves. It is usually hard to eradicate them because of the large infestations. Aphids are not as damaging as some of the other insects that attack broccoli.
    The Cabbage Maggot (Hylemyia brassicae) is a big problem especially with early season plantings. The adult fly deposits eggs just below the soil surface and as the maggots emerge they feed on the roots and thereby depriving the plants from nutrients and water. Brown streaks will develop on the basal part of the stem.
    Cabbage Worms- the imported cabbage worm (Pieris rapae) and the cabbage looper (Trichoplusia ni) both appear as little green larvae. The larvae of the small butterflies can be controlled by Bacillus thuringiensis which is a naturally occurring bacteria that gets inside the insect and damages its midgut.
    The diamond back moth larvae (Plutella xylostella) is an insect that can cause some serious problems in the crops. The cabbage webworm, the corn earworm, and flea beetles are also pests that can pose a problem in broccoli production. The reasons some of these insects are prevailing is because of insecticide resistance by the pest, poor spray coverage, and over wintering populations.

DISEASES
    Clubroot (Plasmodiophora brassicae) is a soil born disease that is quite serious in all crucifers. It is more active in warmer temperatures and acidic soils. The disease stimulates cell division and enlargement which restricts water and nutrient uptake. There are no resistant cultivars and it is easily spread through poor sanitation. It is recommended to maintain the soil at a pH of 7.2, rotate with nonsusceptible crops, use clean transplants, and make sure there is good sanitation.
    Black Rot (Xanthomonas campestris) is a bacteria that causes necrotic areas in the plant. It usually makes the midrib and large veins become black. This organism is seed born so using clean seed would help as well as rotating crops.
    Black leg (Phoma lingam) does very well in cool temperatures. Plants usually get circular black dots that enlarge and get gray centers and eventually the entire plant is affected, stunted and killed.
    Physiological Disorders Buttoning is a physiological disorder that is caused by low temperatures. It is the premature formation of flower heads that are small. Chilling is needed for flowering, but it is hard to estimate how much is needed because of the variance of cultivars. In general, the temperatures need to be 35-50°F for a few weeks for flowers to form. With mineral or nutrient deficiencies a physiological disorder can occur where the flower stalks are hollow.

HARVESTING
    The portion of the broccoli plant that is harvested is the unopened flower buds. The flower head needs to be harvested before the signs of any flower color are shown. It takes about 60-100 days depending on climate and cultivar from planting to harvest. If left too long the stem becomes woody and hard. The mature head can be from 4-7 inches across and can weigh from 0.3 to 1.0 pound each. Harvesting usually takes place at a 4 to 7 day interval in cooler climates to avoid the head becoming overmature. In warmer temperatures the maturity is accelerated and may need to be harvested every 2 to 5 days. After harvesting the main head, side shoots will develop. If the field is properly maintained, 2 to 3 more commercial harvests are possible. The side shoots usually range from 0.1 to 0.3 pounds and are from 1-4 inches. The entire harvest may run from 40-80 days, depending on the conditions.
    Spring broccoli should be harvested in the morning because its susceptibility to wilting.

Field harvest of broccoli

POST HARVEST
Field crates or baskets are used to pack the broccoli in the field. The crates are then taken to the packing shelter and bunched and iced. The plants need to be trimmed and graded. The stems are usually cut from 6 to 8 inches in length and the leaves are removed. The heads are bunched together tightly with twist tie or rubber bands. Broccoli degrades rather quickly and needs to be precooled at 32°F by vacuum cooling, hydrocooling, or ice. Refrigeration is needed during transport for long distances.