Sunn Hemp is one of the only warm season cover crops that adds significant amounts of nitrogen to soils. Because it is a legume, this cover crop has the ability to fix nitrogen from the atmosphere and transfer it to garden soils, making it available for successive crops. It has been reported to add over 100 lbs of nitrogen per acre. This makes it a great option to use ahead of heavy-feeding crops like corn or onions. It also works great for restoring nutrient levels following heavy-feeding crops that consume lots of soil nutrients.
Sunn Hemp is a summer annual that performs well in sandy soils and other soil types that may be nutrient-poor as a result of intensive farming. When cut and incorporated into the soil as “green manure”, it provides a considerable amount of organic matter that will improve soil fertility and tilth. In addition to improving organic matter content in soils, it also suppresses nematode populations as the mowed biomass breaks down in the soil. It is a cover crop that’s very adapted and performs well in dry, hot and windy environments.
Sunn Hemp should be planted when the soil temperature is at least 65-70 degrees Fahrenheit. It may be broadcast and covered or planted with a precision planter such as our Hoss Garden Seeder. It is an extremely fast-growing and fast-maturing cover crop and typically reaches maturity in 8 to 12 weeks. Because it grows so fast, it works great for suppressing and outpacing weed growth during the warmer months when weed pressure is at its highest. As with all cover crops, it should be cut or mowed before going to seed as this will prevent any reseeding issues in the future.
Sunn Hemp Planting Information:
Planting Depth: 1/2″
Seeding Rate: 1.5 lb per 1,000 sq. ft.
Cover Crop Recommendation Chart