Brassica oleracea (Italica Group)
Last revised January 12, 2010
Broccoli plant at Gathering Together Farm, Philomath, Oregon. Photo credit: Alex Stone, Oregon State University
Broccoli, also known as Calabrese in England and much of Europe, is closely related to cauliflower, cabbage, brussels sprouts, and kohlrabi. There is considerable confusion in the scientific and lay literature regarding exact nomenclature. All these Brassicas will intercross readily and are classified in the same genus and species.
To complete the confusion, seed catalogs (especially specialty catalogs) may describe broccoli as heading or sprouting; summer, autumn, or winter; green, purple, dark purple, copper or purplish-brown, sulfur-colored or yellowish-green heading, or white-sprouting! Only the green heading types are discussed below.
BROCCOLI VARIETIES (approximately 75-95 days from seeding, depending on variety, season, and planting date)
Fresh market varieties:
Arcadia, Buccaneer, Emerald City, Emperor, Everest, Excelsior, Green Belt (see note below), Green Valiant, Laguna, Legend, Liberty, Major, Marathon, Pakman, Patriot, Pinnacle, Pirate, Premium Crop, Regal, Shogun, Samurai, Triathlon, Windsor. For trial: Barbados (reported to have good color), Embassy, Green Comet (somewhat heat tolerant), Green Defender, HMX 1134, Idol.
Note: Some new hybrids suitable for fresh market and/or processing have resistance or tolerance to a number of important diseases:
Downy mildew, black rot or both: Belstar F1, Burney F1, Emerald Crown, Emerald Pride, Green Magic, and Millennium F1.
Resistance to Pseudomonas sp. (not Erwinia sp). bacterial head rot: Pirate, Shogun, Green Defender and Green Valiant.
Resistance to club root: Few if any varieties are resistant to club root. Some evidence suggests Emerald Jewel is partially resistant, although Emerald Jewel may not grow well in this region due to insufficient tolerance to abiotic stresses such as heat.
Yellowing in storage: Some recent studies suggest post-harvest application of chemically synthesized plant hormones such as phytosulfokine (PSK) can significantly reduce yellowing during cold storage
Novelty:
Broccoflower: Alverde, Macerta (really, green cauliflowers); Green Harmony (a true broccoli-cauliflower vegetable).
Broccolini: a hybrid of standard broccoli (Brassica oleracea var. italica) with Chinese kale (Brassica oleracea var. alboglabra, also known as Chinese broccoli) which resembles long, slender broccoli side shoots that are nearly ready to flower. The flavor has been described as similar to broccoli but sweeter and less pungent or as resembling asparagus. This hybrid was developed by Sakata Seed Co. and is grown and marketed exclusively in the United States by Mann Packing Co. and Sanbon LLC of California.
Green Sprouting Broccoli: De Cicco, Calabrese, Italian Green Sprouting, Waltham 29 (all early sprouting types).
Kailaan type (Chinese kale or Chinese broccoli, B. oleracea var. alboglabra): Green Lance Hybrid, Gai Lohn.
Romanesco type (unusual spiraled, light green heads): Minaret.
Note: Broccoli Raab, or "Italian turnip" is Brassica rapa. It is a non-heading broccoli-like garden vegetable grown for its asparagus-like early spring shoots. Varieties include: Broccoli Raab, Di Rapa, De Brocoletto, Italian Turnip, Salad Rappone and Spring Rapini.
Important
Before planting any brassica (crucifer or cole crop), consider the following important factors:
1. No crucifer crop, or related weed has been present in the field for at least 2 years, 4 years preferable. Crucifer crops include cabbage, cauliflower, broccoli, kale, kohlrabi, Brussels sprouts, Chinese cabbage, all mustards, turnips, rutabagas, radishes etc. Cruciferous weeds include wild radish, wild mustards etc. Also, crucifer plant waste should not have been dumped on these fields.
2. Soil pH should be 6.5 or higher. Soil pH over 6.8 is necessary to manage club root. The application of 1500 lb/acre of hydrated lime, 6 weeks prior to planting is recommended for soils with pH less than 7.5 for club root control.
3. Arrange to keep transplanted and direct-seeded fields separate to minimize spread of certain diseases that are more prevalent in transplanted fields.
SOIL
Broccoli and other cole crops may be grown on a variety of soils but it does best on a well-drained, loam soil well supplied with organic matter. Sandy loams are preferred for early crops. Adjust soil pH to 6.0 - 6.8 for maximum yields.
SEED AND SEEDBED TREATMENTS
Broccoli seed numbers approximately 144,000 per pound. Most broccoli for processing and fresh market is direct seeded (see section on field seeding below). Some early production of fresh market broccoli is transplanted.
Use certified, or hot-water and fungicide-treated seed to protect against several serious seed borne diseases. Hot water seed treatments are very specific (122 F exactly, for 25 to 30 minutes; the wet seed then quickly cooled and dried). The seed treatments are best done by the seed company, and can usually be provided upon request. Primed seed is now becoming popular. Consult your seed dealer about the availability of primed seed.
TRANSPLANT PRODUCTION
Seedbeds for transplants
Locate these in an open, well drained area, free of club-root. Lime if necessary, and fertilize with 10-30-10 at 600 lb/acre or its equivalent.
When seedlings are to be grown in a seedbed for production of transplants, choose a site where cole crops have not been grown before, or fumigate before seeding according to manufacturer's recommendations.
Always use certified or hot water treated seed for transplant production. Seed in a greenhouse for an early crop, in a cold frame for a less early crop, and in outdoor seedbeds when the weather is warm enough for germination and growth (above 50 F). In each case seed 5-6 weeks ahead of when the plants are wanted for transplanting.
Four to 6 ounces of high quality, sized and density graded seed will provide enough transplants to plant 1 acre. In the seed-bed use a drill with a scatter shoe to drop 15 to 20 seeds per foot in rows 10 inches apart.
Greenhouse transplant production
Precision seed into modular flats, styrofoam trays or blocks of a peat-lite (peat-vermiculite) mix or other suitable growing medium. Crowding should be avoided. Provide 1.5-2.5 square inches per plant in modular trays.
Temperatures should be maintained above 45 F at night and below 85 F during the day. Seven days before transplanting start the hardening off process.
Follow the same process in a cold frame, or seed directly into the covered soil after it has been limed, fertilized and fumigated as for outdoor seed-beds.
FIELD SEEDING
In western Oregon, broccoli is direct seeded in the field between mid April and early July. Fresh market broccoli, and late processing broccoli may be seeded until the end of July.
One-half to 1.5 lb of seed may be used per acre for direct seeding. Pelletizing is not necessary but primed and coated seed is now becoming popular. Consult your seed dealer about the availability of primed seed. In Oregon, broccoli is most commonly direct seeded at about 1 lb of seed per acre. This allows for a pre-thinning spacing of about 45 square inches per plant. By careful attention to planting, and spacings, thinning costs could be minimized.
Use only the highest quality, sized and density graded seed. Seed coating is not recommended.
Use a precision seeder, such as a Stanhay, or Gaspardo vacuum planter, to drop a seed every 3-5 inches within the row. After the first true leaves have formed.
Processing broccoli is planted at a density of about 20,000 to 30,000 plants per acre to produce a large head size. Choose an in-row spacing arrangement that allows adequate plant density and easy thinning (some multiple of the final spacing) which should be about 8-10 inches in the row. Between-row spacing should allow adequate access for cultivation and hand harvest-aid equipment and labor. A common practice is to alternate rows spaced 12-14 inches apart with wider spacings of 28-30 inches for harvest labor and wheel tracks.
Preparation for direct seeding needs considerable attention. A moderately fine-textured soil, free of rocks, clods and trash, firm and very level, is required for precision seeding. Tilling the soil excessively, increases the risk of crusting. Attempt to keep soil aggregates about 1/4 to 1/2-inch in size.
To insure uniform and successful stand establishment, use vermiculite anticrustant or have solid set irrigation available to keep soil moist and free from crusting until the stand has been established.
FERTILIZATION
For the most current advice, see Nutrient Management for Sustainable Vegetable Cropping Systems in Western Oregon, available as a free download from the OSU Extension Catalog
A soil test is the most accurate guide to fertilizer requirements. The following recommendations are general guidelines for western Oregon.
Good management practices are essential if optimum fertilizer responses are to be realized in the production of cole crops. These practices include use of recommended varieties, selection of adapted soils, weed control, disease and insect control, good seedbed preparation, proper seeding methods, and timely harvest.
Because of the influence of soil type, climatic conditions, and other cultural practices, crop responses from fertilizer may not always be accurately predicted. Soil test results, field experience, and knowledge of specific crop requirements help determine the nutrients needed and the rate of application.
The fertilizer application should insure adequate levels of all nutrients. Optimum fertilization is intended to produce top quality and yields in keeping with maximum returns.
The suggested fertilizer applications for broccoli are based on an 18-inch row spacing, with plants 9 inches apart in the row. With decreased row spacing, increased fertilizer rates are suggested.
Recommended soil sampling procedures should be followed in order to estimate fertilizer needs. The Oregon State University Extension Service agent in your county can provide you with soil sampling instructions, soil sample bags, and information sheets.
Where broccoli is direct-seeded, see "field fertilization" section below. If transplants are to be used, and if transplants are to be field grown, fertilize transplant productions beds as follows:
COLE CROP TRANSPLANT BED FERTILIZATION
Broadcast and work into the transplant bed:
1. 40 to 70 lb N/A.
2. Apply phosphorus, potassium, sulfur, magnesium, boron, molybdenum, and lime up to the maximum rates suggested below for field applications.
TRANSPLANTING STARTER SOLUTIONS
Dilute solutions of complete fertilizers high in phosphorus promote quick recovery and early growth of transplants. One-half pint of transplanting solution should be injected into the furrow at the roots of each plant at time of transplanting. A transplanting solution may be prepared by dissolving 3 lb of 11-48-0 or similar mono-ammonium phosphate fertilizer in a 55-gallon drum of water.
FIELD FERTILIZATION
NITROGEN (N)
A total application of 150-200 lb N/A is suggested for broccoli. See other files for recommendations specific to other cole crops. Broccoli growers in the Willamette Valley often use rates of 250-300 lb/A particularly with varieties where several harvests of side shoots would be desired for maximum yields. When high rates of N are used, stem splitting could become a problem and bacterial soft rot may be encouraged by rank growth. Research data indicates that stem splitting might be reduced if the extra N is applied in several sidedressings rather than in one large application.
Broadcast about half of the N just prior to direct seeding or transplanting or band 60-90 lb N/A with the phosphorus. For both direct-seeded and transplanted crops, sidedress 75 to 100 lb N/acre at time of last cultivation, or 1 to 2 weeks before the first cutting. At the higher rates, use two applications, with the first application when the broccoli is 6-8 inches tall and the second about 2 weeks later.
N Solutions such as AN-20 and ammonium thiosulfate may also provide some weed control in broccoli, cauliflower, and cabbage. See the file Nitrogen Fertilizer Solutions Providing Ancillary Weed Control in Cole Crops.
PHOSPHORUS (P)
Phosphorus fertilizer should be banded at the time of seeding or transplanting cole crops. Bands should be located 2-3" to the side of the seeds or plants and 3-4" deep.
| If the soil test* for P reads (ppm): | Apply this amount of phosphate (P2O5, lb/A): |
|---|---|
| 0 - 30 | 150 - 200 |
| 30 - 50 | 100 - 150 |
| Over 50 | 80 - 100 |
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.
POTASSIUM (K)
Limit band applications of K to 90 lb K2O/A. Broadcast remainder of K and work into seedbed prior to planting. The total of N plus K2O in the band should not exceed 90 lb/A. Apply K as follows:
| If the soil test* for K reads (ppm): | Apply this amount of potash (K2O, lb/A): |
|---|---|
| 0 - 150 | 150 - 200 |
| 150 - 200 | 90 - 150 |
| 200 - 250 | 60 - 90 |
| Over 250 | None |
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.
SULFUR (S)
Include 25-40 lb/A of S in the fertilizer program. S is sometimes contained in fertilizers used to supply other nutrients such as N, P, and K, but may not be present in sufficient quantity.
Plants absorb S in the form of sulfate. Fertilizer materials supply S in the form of sulfate and elemental S. Elemental S must convert to sulfate in the soil before the S becomes avail able to plants. The conversion of elemental S to sulfate is usually rapid for fine ground (less than 40 mesh) material in warm moist soil).
Sulfur in the sulfate form can be applied at planting time. Some S fertilizer materials such as elemental S and ammonium sulfate have an acidifying effect on soil.
The S requirements of crucifers can be provided by:
The application of 25-40 lb S/A in the form of sulfate at or prior to seeding or planting.
Applying 40-50 lb S/A as fine ground (finer than 40 mesh) elemental S the preceding year.
Applying coarser ground elemental S at higher rates and less frequently.
MAGNESIUM (Mg)
When the soil test value for Mg is below 2 meq/100g soil, band 15- 20 lb Mg/A at transplanting or seeding time. If Mg deficiency symptoms develop, spray with 10 lb Epsom salts in 100 gal water/A.
Magnesium can also be supplied in dolomite, which is a liming material and reduces soil acidity to about the same degree as ground limestone. Dolomite should be mixed into the seedbed at least several weeks in advance of planting and preferably the preceding year. It can also be supplied by the application of Epsom salts or Sul-Po-Mag fertilizer prior to seeding or transplanting as follows:
* Sul-Po-Mag at 150 to 200 lb/acre.
* OR Epsom salts at 150 to 200 lb/acre.
* OR Dolomitic Limestone at 225 to 275 lb/acre.
BORON (B)
Broccoli is sensitive to boron deficiency. Apply boron as follows:
| If the soil test* for B reads (ppm): | Apply this amount of B (lb/A): |
|---|---|
| 0 - 1 | 3 - 4 broadcast |
| 1 - 3 | 1 - 2 broadcast |
| Over 3 | 1/2 - 1 foliar spray |
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.
A satisfactory foliar spray contains 1 lb B/100 gal water. Fertilizers containing B should not be banded.
Fields East of the Cascades or where winter rainfall is low, and to which the higher rates of boron has been applied should not normally be planted to beans or cucumbers the following year, as both these crops are extremely sensitive to boron.
LIME
If a mineral soil is below pH 6.3 or an organic soil is below 5.5 and/or the calcium (Ca) level is below 8 meq/100g soil lime should be applied. Compared to other vegetables broccoli has a fairly high lime requirement.
The application of lime is suggested when the soil pH is below 6.3
| If the SMP Buffer* test for lime reads: | Apply this amount of lime (T/A): |
|---|---|
| Below 5.6 | 5 - 7 |
| 5.7 - 5.9 | 4 - 5 |
| 5.9 - 6.1 | 3 - 4 |
| 6.1 - 6.3 | 2 - 3 |
| 6.3 - 6.6 | 1 - 2 |
| Over 6.6 | None |
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.
The liming rate is based on 100-score lime. Lime should be mixed into the seedbed at least several weeks before seeding and preferably the preceding year. A lime application is effective over several years.
Some soils may have a fairly high SMP buffer value (over 6.6) but a low pH (below 6.0). This condition can be caused by the application of acidifying fertilizer. In this case the low pH value is temporary and the pH of the soil will increase as the fertilizer completes its reaction with the soil. This temporary "active" acidity from fertilizer is encountered following recent applications of most nitrogen fertilizer materials. Acidifying fertilizers also have a long term acidifying effect on soil that is cumulative and leads to lower SMP buffer readings.
Sandy soils to which fertilizers have not been recently applied also sometimes have low pH but high SMP buffer values. In such cases, a light application of lime (1 to 2 ton/A) should suffice to neutralize soil acidity.
For acid soils low in Mg (less than 0.5 meq Mg/100g soil) one T/A of dolomite lime can be used as a Mg source. Dolomite and ground limestone have about the same ability to neutralize soil acidity.
The P, K, Mg, B, and lime recommendations are based on soil test values from the Soil Testing Laboratory, OSU, Corvallis, Oregon.
These recommendations are largely based on the results of experiments conducted by Oregon State University Agricultural Experiment Station Horticulture and Crop and Soil Science Department research faculty. These recommendations are quoted from OSU Fertilizer Guide FG 27.
IRRIGATION
After the stand has been established, irrigate to maintain uniform soil moisture. About 10-14 inches of water may be necessary in western Oregon depending on seasonal variation, variety, planting date and the number of times the field is harvested.
Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application.
The total amount of water applied, the frequency of irrigation, and the timing of irrigation all may affect the incidence and severity of soft rot of broccoli heads. For a report on irrigation effects on broccoli head rot, see Effect of Frequency and Timing of Irrigation on Yield and Head Rot of Broccoli (1994).
See also the OSU Irrigation Guide for this crop.
BROCCOLI HEADING DISORDERS
Blindness: A percentage of the plants in the field form no heads at all due to some injury. The plant responds by producing numerous shoots at near ground level. The injury can be due to insect (cabbage maggot, lygus bug, diabrotica) damage to the growing point usually when the plant is small, or if these occur just at the beginning stages of head initiation.
Leafy heads: The presence of leaves within the head is often due to high temperature coupled with lush growth due to excess water and nitrogen.
Large, coarse buds: Bud size is a function of variety, but all develop large buds as the heads become mature. High temperature and delayed harvest may result in excessively large or open buds. Varieties differ in their field holding characteristics.
HARVESTING, HANDLING, AND STORAGE
In the Willamette Valley, broccoli harvest for processing begins about June 25 and continues to October 31. The prime harvest period for processing is July 15 to the end of September.
Yields of processing broccoli average approximately 5.5 tons/acre with good yields at 7.5 tons.
Harvest broccoli heads when the buds are still small and tightly closed, and before the heads are fragmented. Heads should be tight, and the individual flowers in the clusters should not show yellow petals. Side heads develop rapidly in some varieties following removal of the terminal head, and harvesting may continue for several weeks.
Broccoli is highly perishable, and it is usually held for only a brief period as needed for orderly handling. If in good condition and held with adequate air circulation and spacing between containers to avoid heating, broccoli should keep satisfactorily 10-14 days if held at 32 F, 90-95% humidity.
PACKAGING
For fresh market two or three heads are bunched together and packaged 14-18 bunches per 20 to 24-lb "half carton" container. Containers should be liquid iced for quick cooling and maximum shelf life.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Store broccoli and 32 F and relative humidity of 95 to 100 %. Broccoli is highly perishable, and it is usually stored for only a brief period as needed for orderly marketing. Broccoli should be hydrocooled or packed in ice immediately after harvest and kept at 32 F to maintain good salable condition, fresh green color, and vitamin C content. If in good condition and stored with adequate air circulation and spacing between containers to avoid heating, broccoli should keep satisfactorily 10 to 14 days at 32 F. Longer storage is undesirable because leaves discolor, buds may yellow and drop off, and tissues soften. The respiration rate of freshly harvested broccoli is very high - comparable to that of asparagus, spinach, or sweet corn. Thus, like these crops, broccoli must be cooled immediately after harvest to rapidly lower the respiration rate and be kept at low temperature for maximum shelf life.
A controlled atmosphere of 10% carbon dioxide and/or 1% oxygen can increase the shelf life of good quality broccoli held above 40 F. An atmosphere with 10% carbon dioxide retards yellowing and toughening, and one with 15% carbon dioxide has the same retarding effect but can induce persistent off-odors. A 1% oxygen atmosphere retards yellowing but one with 0.1 to 0.25% oxygen can cause severe injury and result in off-odors and off-flavors in cooked broccoli. Broccoli should not be stored with fruits, such as apples or pears, which produce substantial quantities of ethylene, because this gas accelerates yellowing of the buds.