What it is
Sunn Hemp (Crotalaria juncea) is in the Fabaceae (Legume) family. A fast tropical legume that produces huge biomass and nitrogen in a single hot summer. Not for eating.
How to grow it
It wants full sun, water it low, and give it tolerant soil. Target a soil pH around 5.0–7.5. Space plants about Broadcast apart. Expect roughly Summer cover. Warm-season annual.
How it's used
Sunn Hemp is used: cover crop only.
🔎 How to identify it
- Narrow simple leaves
- Tall slender stems
- Yellow pea flowers
Not for eating
How to grow & propagate sunn hemp
Everything I've worked out about starting this one, keeping it alive through a Texas year, and turning one plant into many — free.
How to propagate sunn hemp
Legumes resent transplanting — that taproot wants to go straight down — so sow them right where they'll grow once the soil has warmed. Soak hard-coated seed overnight to speed germination. As a bonus, this whole family pulls nitrogen out of the air and banks it in the soil, so wherever you grow them you're feeding next season's crop.
Growing sunn hemp in Texas
Give it full sun and tolerant soil. Match the spot to the plant and most of the battle is already won.
This one thrives in heat that flattens other plants, so it earns its space through a Texas summer. Get it established before the worst of July, keep water steady, and it'll produce when little else will.
Keep moisture even, especially while it's young — deep, less-frequent soaks build better roots than a daily sprinkle.
Harvesting
Figure on roughly summer cover before you're harvesting.
Making more for free
If you want more, let your healthiest plants mature fully and collect the seed once it's dry on the plant — then store it somewhere cool, dark, and dry until next season.
Part of the free Texas Roots plant database, compiled by Jordan Polasek from his greenhouse in El Campo, Texas. Free to read and share. If it helped, the best thanks is to grow something.