Your Download

Complete the form below to gain access to this publication. You'll be subscribed to our email list. We won't ever share your info with anyone, and you may unsubscribe at any time.
  • This field is for validation purposes and should be left unchanged.

  • Skip to primary navigation
  • Skip to main content
  • Skip to footer

Organic Seed Alliance

Advancing ethical seed solutions to meet food and farming needs in a changing world

  • News
  • Programs
    • Research
    • Education
    • Advocacy
  • Publications
    • All Publications
    • How-to Guides
    • Reports
    • Webinars
    • Worksheets & Record-keeping
    • Conference Proceedings
  • Resources
    • 2023 Policy Platform for Seed
    • State of Organic Seed
    • Organic Seed Producers & Intern Host Farm Directory
    • Variety Trial Tool
    • Seed Patent Watch
    • Seed Internship Program & Organic Seed Production Online Course
    • Seed Economics Toolkit
  • Events
    • Upcoming Events
    • Organic Seed Growers Conference
    • COVID-19 Protocols
  • Media
  • About
    • Staff Directory
    • Board & Advisors
    • Our Story
    • Our Values
    • Our Alliance
    • Commitment to Racial Equity
    • Business Partners
    • Annual Report
    • Contact Us
    • FAQ
  • Give

July 23, 2018

Broccoli Seed Production: Quick Reference

Print Friendly, PDF & Email

Broccoli Seed Production: Quick Reference - Organic Seed Alliance

Figure 1. Flowering broccoli. These plants have not been staked, but may need to be when the seed is maturing.

Broccoli Seed Production

Broccoli is both an annual and biennial crop depending on whether you are producing seed of a sprouting or heading type of broccoli. Sprouting broccoli will require vernalization (6-8 weeks of cold accumulation) before flowering and seed production will occur.

Broccoli growth habits
Beinnial Sprouting types
Annual Heading types

Production

Broccoli likes moderate temperatures between 60-75°F. When temperatures exceed 90°F for extended periods, pollination and early seed set can be negatively affected. Broccoli also likes early season moisture, which encourages rapid growth. Climates with mild springs, relatively mild summers, and dry fall conditions are ideal for broccoli seed production. Once heading begins, too much moisture can encourage head rot and disease. Seed development is best when conditions are dry. Broccoli likes well balanced soils and has a high demand for boron and molybdenum (Mb). Deficiencies in molybdenum can cause whiptail. To make molybdenum more available in your soils, ensure a low pH of 5.5. Otherwise, pH between 6.0 and 6.6 is optimal. Broccoli is insect-pollinated and self-incompatible, which ensures outcrossing unless hand pollination is used before the flowers open (bud pollinating). Many insects are effective pollinators.

Annual heading broccoli varieties are weak biennials and vernalization needs are generally met by cool nighttime temperatures. These types are planted in the spring for late summer or early fall seed harvest. Biennial sprouting broccoli varieties require full vernalization and must either be overwintered in the field or kept in cold storage for at least 8 weeks. These types are usually transplanted in mid- to late summer to ensure two-thirds of growth is attained before the onset of winter. For both types, seed should be started in a greenhouse (more common for colder climates, such as the Intermountain West) or nursery bed and transplanted after 4-6 weeks, ensuring that seedlings do not experience temperatures lower than 50°F for extended periods. Cold temperatures cause “buttoning” or premature bolting. Plants should be spaced 18-24 inches apart in rows that are 2-3 feet apart. Broccoli flowers should be fully formed before the onset of summer heat when aphids begin to be a problem and pollination can be reduced by high temperatures. In fields where wind is a problem, staking will be necessary once plants achieve full seed production maturity size. Even without consistently windy conditions, staking may be necessary since the plants often can’t support the weight of the flowering shoots and developing siliques.

Figure 1. Flowering broccoli. These plants have not been staked, but may need to be when the seed is maturing.

Broccoli will flower over an extended period of time. Thus, seed will also mature over a period of time. When the seed pods (silques) turn light tan or buff colored, the plants are ready to harvest. When 60-70% of the silques are ready, cut the plant at ground level, windrow, and dry for another 1-2 weeks in the field or in a well ventilated hoophouse or greenhouse.

Figure 2. Windrow of broccoli seed.

When seeds are mature and adequately dry, the silques will break open easily to release the seed. For small amounts of seed, thresh by hand – rub between your hands, bang the plants with a threshing stick, walk on the plants on grass or another soft surface, or bang plants on the inside of a container or tote. For larger amounts of seed, run over windrows with a truck or tractor as long as the windrow is on a soft surface such as grass. Do not thresh on a hard surface such as gravel or concrete as seed may crack or get smashed. Once threshed, winnow, scalp with a pitchfork, or rough screen with a large gauge screen to remove the majority of the chaff.

Figure 3. Scalping brassica seed with a pitchfork.

Use a combination of winnowing and screening to clean the remaining seed. Use hardware cloth or precision cut round-holed metal screens with diameters smaller than the seed to remove fine debris. Final processing may require an air separator or spiral separator.

Figure 4. Freshly threshed broccoli siliques. Seed is under the siliques and chaff at the bottom of the bucket.

Selection and Variety Improvement

Grow between 50-90 plants to retain population vigor. Because open-pollinated varieties are often variable, plant at least 130 plants to allow for continual selection and roguing. For sprouting types, eliminate plants that flower before winter (and full vernalization) and select for cold hardiness after overwintering. For heading types, domed heads with tight beads are best as they shed water, which helps to prevent disease.

Trait Timing
Seedling vigor/damping-off resistance 1-2 weeks after emergence
Leaf type Head harvest
Leaf color Head harvest
Plant stature Head harvest
Plant vigor Month after transplanting; head harvest
Disease presence Before heading (25-40 days after transplant); head harvest
Insect pest pressure Before heading (25-40 days after transplant); head harvest
Head size Head harvest
Head shape Head harvest
Head color Head harvest
Bead size Head harvest
Time of head harvest Head harvest
Harvest window At each head harvest
Side shoot production At each head harvest
Flavor, texture, eating quality After head harvest

Disease

Use disease-free seed and a 3-5 year crop rotation (5 for diseases like Black leg). Eliminate wild crucifer weeds that may host diseases. Avoid overhead irrigation and water only in the morning. Increase plant spacing and orient rows toward prevailing winds to minimize disease. Incorporate residues into the soil to prevent overwintering diseases. Some states regulate Black leg, so if selling out of state, you may be required to test for the presence of this disease. Diseases are classified by severity with a class of 1 being the most severe and 3 the least severe.

Disease Type Severity class Favorable conditions Control measures
Black rot (Xanthomonas campestris pv. campestris) Seedborne 1 Warm and humid following a period of rain during early development Hot water (25 min. at 122°F)
Xanthomonas leaf spot (Xanthomonas campestris pv. amoraciae) Seedborne 1 Prolonged periods of dew or rain over a wide range of temperatures
Xanthomonas leaf spot (Xanthomonas campestris pv. raphani) Seedborne 1 Prolonged periods of dew or rain over a wide range of temperatures
Black leg (Phoma lingam) Seedborne 1 Rainy, cool weather Hot water (25 min. at 122°F)
Black spot (Alternaria brassicicola) Seedborne 1 Moderate temperatures (60-80F) and high humidity
Alternaria diseases (Alternaria brassicae) Seedborne 1 Moderate temperatures (60-80F) and high humidity Hot water (25 min. at 122°F)
Downy mildew (Peronospora parasitica) Seedborne 3 Cool (45-60F) and moist
Fusarium wilt (Fusarium oxysporum f. sp. Conglutinans) Seedborne 3 Hot (80-90F) and humid
Peppery leaf spot (Pseudomonas syringae pv. maculilola) Seedborne 3 Cool and rainy
Verticillium wilt (Verticillium dahliae) Seedborne 3 Cool and moist
White rust/White blister (Albugo candida) Seedborne 2 Cool and wet
Clubroot (Plasmodiophora brassicae Wor.) Root
Root knot (nematodes) Root
Bacterial head rot (Pseudomonas spp. Pectobacterium carotovorum) Foliar
Alternaria head rot (Alternaria spp.) Foliar
Cabbage worms Insect
Aphids Insect
Flea beetles Insect
Whiptail Mb deficiency

This resource was made possible thanks to the Montana Department of Agriculture’s Specialty Crop Block Grant Program. 

Crops: Broccoli

Publication Categories: How-to Guides

Tags: Seed Production, Seed Quality

Latest Tweets

Footer

Advancing ethical seed solutions to meet food and farming needs in a changing world

  • Email
  • Facebook
  • Instagram
  • Twitter
Subscribe to Our Newsletter

Copyright © 2023 Organic Seed Alliance · All Rights Reserved · Website by Tomatillo Design