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New Sunn Hemp Cover Crop

Standard · Fabaceae

New sunn hemp is a fast-growing tropical legume cover crop grown for warm-season biomass, nitrogen fixation, weed suppression, and root activity between cash crops. Plants can reach 4-6 feet or taller in a short window and are most valuable when terminated before heavy seed set. In home gardens it is best used as a summer soil-building crop in open sunny beds with warm soil and good drainage. Key facts: 60–90 days to maturity, 8+ hours of sun, 12–18 " spacing. Not recommended for containers.

Updated April 19, 2026 · Backed by 4 cited sources
Overview

At a Glance

The essentials first: timing, light, spacing, seed-starting, container fit, and overall size.

Days to maturity
60–90 days
Sun
8+ hours
Full Sun, 8+ Hours
Spacing
12–18 "
between plants
Seed start
0 weeks
before transplant
Container
Not recommended
Needs 10+ gal if attempted
Height
4–6 ft
at maturity
Planting window

Zone Planting Guide

Switch zones to see whether this plant is a strong fit, what frost timing looks like, and any extra notes worth planning around.

This card updates instantly with viability, frost timing, and any planting notes for your selected zone.

Resilience

Plant Health

Stress tolerance, resistance notes, and the most common problems to watch for as plants mature.

Tolerance
Heat: High Cold: Low Drought: Moderate

Common Issues

Poor Establishment

Cause: Cool soil or early weed pressure can thin the stand before the crop gets moving.

Prevention: Sow into warm soil and a clean seedbed.

Waterlogging

Cause: Roots decline in poorly drained or salty soils.

Prevention: Use well-drained ground and avoid low wet pockets.

Woody Stems

Cause: Letting the crop run too long creates coarse stems that break down slowly.

Prevention: Terminate in the recommended 60-90 day window or around early bloom.

Feeding & picking

Nutrition & Harvest

How hungry the plant is, what ripe harvest looks like, and how long the crop keeps after picking.

Feeding
Nutrition
Feeding intensityLow feeder
RecipesWorm Castings Topdress
Timing
Harvest

Mow or incorporate when the stand is dense and vigorous, ideally before heavy seed set and before stems become too fibrous.

Expected yield0.2–0.5 lbs/plant
Storage Use immediately as mulch, compost feedstock, or green-manure residue.
Plant relationships

Companion Planting

Helpful neighbors can support growth or deter pests. Keep antagonistic plants separated to reduce stress and competition.

Avoid planting near
Herb Fennel
What you'll need

Growing Supplies

Based on New Sunn Hemp's growth profile -- recommendations matched to this variety's specific requirements.

Drip irrigation / soaker hose kit

Every gardener benefits from putting water at the root zone instead of on the leaves, because drip and soaker systems reduce foliar disease pressure by limiting leaf wetness and soil splash. A quality kit should include a backflow preventer, filter, pressure reducer, and UV-resistant tubing.

Source: Iowa State University Extension; Colorado State University Extension; UMass Extension

Soil test kit

A soil test gives a baseline for pH and nutrient status so gardeners can add only what the soil actually needs. Prioritize a mail-in or lab-affiliated kit whenever possible because extension guidance notes that laboratory testing is more accurate than instant readers.

Source: University of Maryland Extension; Purdue Extension; Montana State University Extension

Quality bypass pruners

Extension guidance favors bypass designs because they make cleaner, closer cuts on living tissue than anvil types. Look for hardened steel blades that can be sharpened, a comfortable grip, and a cutting capacity matched to real home-garden stems.

Source: University of New Hampshire Extension; Iowa State University Extension; Purdue University Extension

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Research

Sources

Reference material and extension guidance used to build this growing guide.

seed_catalog Seeds Nowuniversity Oklahoma State University Extensionreference NRCS sunn hemp cover crop bulletinuniversity Colorado State University Extension
Internal links

New Sunn Hemp Cover Crop Planting Dates by Zone

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