Tuesday, March 4, 2014


"Sunn hemp is an excellent choice for a summer cover
crop for Florida growers because it returns nitrogen to
the soil, suppresses weeds and nematodes, improves soil
tilth and water holding capacity, and reduces erosion in
fields otherwise left without plant cover.

Sunn hemp forms a symbiotic relationship with soil bacteria that remove
nitrogen (N) gas from the atmosphere and transforms N to
plant-available forms.
This article summarizes the recommended cultural practices
to help vegetable growers grow a successful summer
cover crop and to optimize the amount of nitrogen that is
returned to a vegetable crop."

What works in vegetables really works in grain crops as we try to increase yields.  My fertility program would work well in many vegetable programs and I have grown sweet corn and green beans.

It likes a little bit more sunshine than we receive here in southern Ohio, though it has been successfully used here.  Have any of you planted sunn hemp?  What are your results with it?

Lots of farmers are just starting to experiment with cover crops.  When can I plant them, how do I plant them, what rate of seed?  The list goes on and on.  Some are working with sunn hemp but it looks like marijuana growing wild and that just doesn't seem to jive with a corn-soybean rotation!

If you are looking for a better way to produce nitrogen on your farm and you grow wheat, sunn hemp should probably be in your mix of cover crop seeds.  If you are my location east to west or farther south, it will be easier for you to grow and benefit from its many attributes, mainly nitrogen fixation.

Like I've told people about radish the last ten years, sow some and watch what happens.  I think every farm should have a grow lab of some sort to plant different seeds and watch them grow.  The better farmers I talk to and work with do this.

Ed Winkle


  1. We found some "hemp" in a patch of woods next to the river. It was kind of a "grow lab." It was a father-son operation. They were pretending to be fishing. You could kind of tell what they were doing. The landlord called the sheriff. Strange thing about it is that in OR you can just get a grow card which makes it all legal.

  2. There's a blog at: http://farmingsweetbay.wordpress.com/ about planting different cover crop cocktails on a small farm, and she has planted sunn hemp in those mixtures a couple of times.

    The one that interested me was a mixture of sorghum-sudangrass and sunn hemp she planted last summer. Without any additional fertilizer, it was over 8 feet tall by the time she mowed it in the fall.

    If I could find some affordable seed, I've been thinking I might try planting it with a planter at about 5 lb/acre, or in a mix with millet and/or sorghum-sudangrass.

  3. I guess I will finally show my ignorance here and ask, what exactly is a "cover crop" and what is it's purpose? Seriously. I don't think we even have them here in Sask. Not on my farm anyway.

  4. Thanks, all. Ralph, Organic Gardening says, "Cover crops just might be the hardest-working plants you’ll ever grow. Cover crops (also called green manure) suppress weeds, build productive soil, and help control pests and diseases. Plus, cover crops are easy to plant and require only basic care to thrive. And they grow well in nearly every part of the country."

    Very simply, they are a crop planted not for harvest but to enrich the soil. Until recent years, farmers harvested every crop they grew for feed, whether it was fall planted or not. We planted Timothy with wheat then frost seeded clover in late winter. That was taken off as a hay crop for a year or two.

    The simplest cover is a grass like rye planted in the fall. Several broadleaf crops like Crimson Clover or Winter Peas were tried until the forage radish really caught on like fire. Mother Nature's winter annuals cover the soil but don't enrich it much. I don't consider them a cover crop.

    Good question!


  5. I've disced some under and it is a miserable experience. Tough stringy stuff that doesn't break down.There are some good legumes out there; why bother planting this weed?

    1. You probably waited too long, and let it get fibrous. Why choose sunn hemp over other legumes? virtually all major legume cover crops are good hosts for root knot nematodes. sunn hemp inhibits this pest, and it grows during warm season when nematodes are active. If nematodes are of no concern, and you prefer a winter cover crop, go with hairy vetch. it's one of the best in nitrogen fixation and weed suppression. Just don't let it go to seed! (or it will 'weed-suppress' your crops)