Our Trial: Sunn Hemp as a Cover Crop

sunn hemp cover crop

Finally, a real farm post!

We planted sun hemp on our farm as a late summer/early fall cover crop.  Like everything else in life and farming, Sunn Hemp has some pros and cons but was overall quite impressive and we will probably plant it again.  We planted it as part of a federal study to help people solve problems on farms.  We were looking for a midsummer cover crop that would fix nitrogen, prevent erosion and not be a draw for deer. We received a small grant and free seeds to participate in the study.

On the sunny side, sunn hemp is one of the few cover crops that grows well in summer, the deer are not interested in it and it can withstand heat and drought.  We planted it in poor sandy soil and did not irrigate.  It produces a very impressive amount of biomass which can be knocked down for a green manure or moved around as mulch.  Our stand reached six feet tall and had woody stems and lovely yellow spike flowers.

On the down side, some sunn hemp varieties are toxic to livestock and fowl so use caution and do your research when selecting a variety for your farm.  Also, the plant has the potential to become invasive in the south.   According to the USDA, “since sunn hemp will not set seed consistently north of 28N latitude (slightly north of Corpus Christi, TX), it has little potential for becoming a weed.”  So it sounds like we are safe to plant it in Maryland. (Source: USDA: Sunn Hemp: A Cover Crop for Southern and Tropical Farming Systems)

Sunn Hemp has an interesting history and is widely grown in India where it originated and is used for all kinds of things including forage and fiber. It is also widely grown in Hawaii year round.    According to the Handbook of Energy Crops by James Duke, “Sunnhemp is cultivated for the strong bast fiber extracted from the bark, which is more durable than jute. Fiber is used in twine, rug yarn, cigarette and tissue papers, fish-nets, sacking, canvas and cordage. Sunn fiber is stronger when wet, and is fairly resistant to mildew, moisture and microorganisms in salt water. It is one of the oldest known fibers in the Indo-Pakistan subcontinent, as mentioned in ancient Sanskrit literature.”  (Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.). 

While we don’t plan to weave any rugs out of our crop, it certainly seems like a plant with lots of potential to control erosion and add nitrogen add organic matter to the soil.  As an added bonus, I cut a bouquet in the fall and it lasted a week in a vase and may have potential as a cut flower  or filler for late season bouquets.

This article appeared in the Maryland Organic Food and Farming Association (MOFFA) Winter Newsletter.  You can learn more about Moffa here.

4 Comments:

  1. So glad I’m not the only person who thinks it has potential as a cut flower! And cutting off the flowers likely keeps the accumulated nitrogen in the leaves, so win-win. Of course, I think goldenrod makes a good cut flower too, so maybe I just have a predilection for weedy bouquets.

  2. Did the USDA provide this grant to your farm? I am working with a school district in SC and we are going to be doing a student led project on cover crops, and any additional funding would be great, so I am open to suggestions of places to look for grant money.

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