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Ohio State University Extension


Sunn Hemp as a Cover Crop in Ohio

Agriculture and Natural Resources
Sarah Noggle; Educator; Food, Agriculture, and Environmental Sciences; Ohio State University Extension, Paulding County
Rachel Cochran; Extension Associate, Water Quality; Food, Agriculture, and Environmental Sciences; Ohio State University Extension, Paulding County

Information gathered from the Midwest Cover Crops Council (MCCC) was used to compile this summary on how to use sunn hemp as a cover crop in Ohio. For more information, see the Midwest Cover Crops Field Guide, Third Edition, and the Cover Crop Selector Tool found at: view of multiple plants with long, green stems with smooth leaves and yellow flowers growing along the upper length of the stem.


  • Smooth trifoliate leaves
  • Yellow flowers
  • Extensive taproot

Cultural Traits

  • Summer annual
  • Minimum germination temperature: 42 degrees Fahrenheit
  • Reliable establishment window (state average): June 10–Aug. 16
  • Upright growth habit: 3–9 feet
  • Preferred soil pH: 6.5–7.5
Table 1. Rating the traits of cover crop sunn hemp.
Heat tolerance Excellent
Drought tolerance Excellent
Shade tolerance Very good
Flood tolerance Very good
Low fertility tolerance Excellent
Winter survival Winter-killed


  • Drilled at ¼–½ inch
    • 14–20 lb./acre (pure live seed)
  • Broadcast with shallow incorporation
    • 16–22 lb./acre (pure live seed)
  • Broadcast without incorporation is not recommended

Additional planting information:

  • 15,900 seeds per lb.
  • Inoculation type: sunn hemp.
  • When planting on slopes or using for forage/grazing, increase seeding rate.

Disclaimer: Rules for Financial Assistance Program Recipients
Individuals participating in financial assistance programs are required to follow Natural Resources Conservation Service (NRCS) Appendix A regarding seeding rates and dates. Failure to do so will jeopardize payments. Appendix A can be found in Ohio’s Field Office Technical Guide, Section 4, Ecological Sciences Tools:


  • Dry matter = 1,000–4,000 lb. per acre, per year
    • Biomass quantity is highly dependent on planting/termination dates and precipitation.
  • Total nitrogen = 50–150 lb. of N per acre (not fertilizer replacement).
    • Plant early in the season (June) for full nitrogen potential.
    • Performance is weather dependent.
    • Sunn hemp needs proper inoculant to increase nitrogen content.

Additional performance information:

  • Sunn hemp produces a high-fiber residue.
  • Forage is suitable for goats/sheep but is less suitable for cattle grazing.
  • Seeds contain alkaloids, which are toxic to livestock; therefore, avoid grazing after flowering.
  • Bloat potential is easily managed by restricting to 30% of total ration or by mixing with a grass.
Table 2. Rating the attributes of cover crop sunn hemp.
Nitrogen source Good
Soil builder Good
Erosion fighter Good
Weed fighter Good
Grazing Good
Quick growth Good
Lasting residue Very good


  • Tillage
    • If terminating with only tillage, multiple passes are often required.
  • Chemical

Additional termination information:

  • Mature sunn hemp has fibrous stems that may be difficult to no-till drill into.
  • Follow NRCS guidelines for cover crop termination dates to comply with crop insurance.
Table 3. Potential advantages of cover crop sunn hemp.
Soil Impacts
Subsoiler Excellent
Frees phosphorus (P) and potassium (K) Excellent
Compaction fighter Very good
Chokes weeds Good
Attracts beneficials Good
Bears traffic Excellent

Potential Disadvantages

Delayed emergence: occasionally a minor problem

Increased weed potential: could be a minor problem

Increased insects/nematodes: could be a moderate problem

Hinders crops: could be a minor problem

Establishment challenges: occasionally a minor problem

Mature incorporation challenges: could be a moderate problem


This publication was adapted with consent from the Midwest Cover Crops Council (MCCC) with content from the Midwest Cover Crops Field Guide, Third Edition, and Cover Crop Selector Tool ( It was created under a joint project with MCCC to produce customized introductory guidance about cover crops for all member states/provinces. Ohio cover crop recipes can be found at

The Midwest Cover Crops Council ( aims to facilitate widespread adoption of cover crops throughout the Midwest by providing educational/outreach resources and programs, conducting new research, and communicating about cover crops to the public.

Funding for this project was provided by the McKnight Foundation.

Red rectangle with white lettering spelling McKnight Foundation.



Originally posted Apr 6, 2023.