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

Carrot Seed Production: Quick Reference

Print Friendly, PDF & Email

Carrot Seed Production: Quick Reference - Organic Seed Alliance

Figure 8. Carrot umbels ready for threshing.

Carrot Seed Production

Carrots are a biennial, so seed production must take into account a two-year reproductive cycle.

Year 1: Producing the carrot crop

Carrot production is most successful with dry, warm to hot summers in sandy or silty loam soils with high nitrogen and phosphorus but without excess nitrogen. Carrots prefer a soil with a high water-holding capacity and need a consistent water supply. They should be direct seeded in early summer and thinned to 1-2 inches apart. Once some roots have reached market size, selections can be made for desirable root characteristics.

Figure 1. Carrots being selected for root characteristics including shape, color, and core distribution.

Above ground characteristics (foliage and crowns) can be selected for during the growing season. Similar to onions, carrot populations need to be maintained with at least 120-200 plants, so initially select 225 or more since some may be lost to rot during the winter storage. Roots can be harvested when the soil is moist, but not wet. Any soil clinging to the root should be wiped off by hand. Do not wash the roots or rub them with a brush. Save only disease-free, true-to-type roots. Trim the tops to ½ inch above the root crown, taking care not to remove the apical bud. Store the roots at 34-38°F and 90-95% RH.

Year 2: Producing the carrot seed

Carrot is highly outcrossing and insect-pollinated. It must be isolated from other carrot varieties as well as wild carrot (Queen Anne’s Lace) by at least 0.5-2 miles unless the flowering plants are enclosed in a cage. Time planting so that seed set will happen when temperatures between 75-90°F. Before planting the stored roots, cut the bottom third of the root to select for root color or core structure (this can also be done at the time of root harvest to avoid storing roots with undesirable internal characteristics). Allow the cut roots to heal over for a few hours before planting. The roots should be planted 12 inches apart with the crown just above the soil’s surface. Avoid overhead watering to reduce the potential for disease. Carrots flower over an extended window of time, with the first and largest umbels (known as the primary or king umbels) at the top of the plant opening and maturing first, followed by increasingly smaller and later maturing sets of flowers down the plant. If feasible harvest the primary umbels when they have begun to brown and the seeds are visibly brown and fully formed. Continue to harvest as umbels mature until either all umbels with fully mature seeds have been collected or until a satisfactory amount of seed has been gathered. Lay cut umbels out on landscape fabric, or other breathable cloth, and allow to fully dry.

Figure 2. Carrot umbels ready for threshing.

Use a combine to harvest large acreage, aiming to cut the crop when approximately 70% of the umbels have mature seed. It is preferable to dry carrot seed to 7% moisture or slightly less. Thresh seed by rubbing the umbels by hand, against a screen, or by stepping on a pile of them.

Figure 3. Threshing seed by stepping on it. Always do this with soft ground underneath.

Clean the seeds with a combination of winnowing and screening. To remove fine sticks, an indent cylinder may be helpful. Debearding with soft brushes can remove the fine hairs on the seed coat and prevent the seed from clumping. Seed stored at 40-60°F and <40%RH will last 3-4 years.

Figure 4. Carrot seed often has many fine sticks. Winnowing and the use of an indent cylinder may help with removing them.

Selection and Variety Improvement

Selections for foliar traits, root characteristics (such as external and internal color(s), shape, size, skin smoothness, and flavor) and resistance to disease and bolting should be made in year one when roots are fully mature. Plan to make selections during and after storage as well, selecting roots that have maintained quality, have not grown excessive root hairs, and have not succumbed to disease or rot while in storage. Always discard and never replant any diseased or rotten roots.

Trait Timing
Seedling vigor 2-3 weeks after seedling emergence
Top height Shortly before root harvest
Top density Shortly before root harvest
Top strength Shortly before root harvest
Root tip fill At or shortly after root harvest
Root smoothness At or shortly after root harvest
Degree of root forking At or shortly after root harvest
Shoulder quality At or shortly after root harvest
Root uniformity At or shortly after root harvest
Root shape & color At or shortly after root harvest
Disease resistance During growing season and after harvest
Insect resistance During growing season and after harvest
% Marketable roots At or shortly after root harvest
Marketable yield (whole plot & weight per root) At or shortly after root harvest
Storagability Periodically throughout winter, 2-8 months after harvest
Flavor – sweetness At harvest, and periodically for the next several months
Flavor – harshness (bitter) At harvest, and periodically for the next several months
Flavor – pineyness (acidic) At harvest, and periodically for the next several months
Flavor – perfumeyness (floral) At harvest, and periodically for the next several months
Texture At harvest, and periodically for the next several months

Disease

Plant disease-free seed. Use furrow or drip irrigation. Use a 3-year crop rotation. Bury carrot residues. 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
Bacterial leaf spot (Xanthomonas campestris pv. carotae) Seedborne 1 Warm (77-86°F) temperatures and rain or overhead irrigation Hot water (20 min. at 122°F)
Black rot/Black crown (Alternaria radicina) Seedborne 1 Warm/hot (above 65°F) and extended wetness of foliage
Alternaria leaf blight (Alternaria dauci) Seedborne 1 Warm and moist with wide temperature range (57-95°F) Hot water (20 min. at 122°F)
Cercospera leaf blight (Cercospera carotae) Seedborne 2 Warm and moist with wide temperature range (57-95°F) Hot water (20 min. at 122°F)
Itersonilia canker (Itersonilia perplexans) Seedborne 3
Aster Yellows – virus Foliar
Carrot Rust Fly (Psila rosae Fab.) Insect

Also see Principles and Practices for Organic Carrot Seed Production in the Pacific Northwest.

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

Crops: Carrots

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