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 unpublished.).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.

Now Starring (drumroll please) the Cover Crops

rye grass

On a farm, cover crops usually play supportive roles at best.   Unglamorous crops like clover and vetch never get the shiny magazine spreads reserved for trendy heirloom tomatoes or the newest hydrangea cultivar.  They just quietly hold down the soil, fix nitrogen, provide food for the pollinators and create biomass to enrich the soil.  It sounds like enough to me for a starring role, but cover crops are almost always considered second fiddle to the crops.

Vetch and Austrian Winter Pea flowering

But right now, the cover crops are having their moment to shine. The crimson clover is topped with dramatic red blossoms, the vetch is covered in purple flowers and the rye is five feet tall, a lovely blue green color and will sway in the slightest breeze.  All the pollinators from miles around are feasting on the flowering vetch and clover and for added drama, all of these crops will be mowed down soon before they go to seed.

The first food crops of the season are a huge treat, but before we turn our attention to the expected spring stars — like radishes, green onions and dozens of kinds of lettuce — let’s give the cover crops their moment in the sun.  It is well deserved.

P.S.  I have a piece on the Jewish parenting blog Kveller today with Jewish (farming) view of Mother’s Day. Check it out and leave a comment, here and or there. Thanks for reading and happy Mother’s Day.