sunn hemp
Crotalaria juncea · Fabaceae
sunn hemp (Crotalaria juncea) is a annual herbaceous plant in the Fabaceae family. It is introduced to North America rather than native. USDA records it as hardy in zone 10 and warmer, down to about 32°F.
At a glance
| Type | forb-herb USDA |
|---|---|
| Lifecycle | annual USDA |
| Native status | introduced USDA |
| Mature height | 5 ft USDA |
| Light | full-sun USDA |
| Water need | high USDA |
| Growth rate | rapid USDA |
| Soil pH | 5–8.4 USDA |
| Flower color | Yellow USDA |
| Hardiness zones | 10 and warmer USDA |
| Guild layer | nutrient Derived |
| Nursery availability | Routinely Available USDA |
USDA quoted from the USDA PLANTS database · Derived computed by a fixed rule from those columns. No value on this page is estimated.
Growing conditions
It needs full sun. USDA rates it as having needs consistently moist ground. Its drought tolerance is rated medium. It handles periodically wet ground (USDA rates its anaerobic tolerance medium). It is recorded on soils from pH 5 to 8.4 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 10.
Size and growth
At maturity it reaches about 5 ft, making it roughly waist to chest height. It grows quickly.
Foliage, flower and season
Summer foliage is green, medium in texture. Its flowers are conspicuous. Its fruit or seed heads are conspicuous, extending interest past flowering. Its active growth period is year round.
What the site needs to provide
USDA records it across sites receiving 20 to 169 inches of annual precipitation. It needs at least 360 frost-free days to finish its season. It roots to at least 16 inches. Fertility requirement: low — no feeding needed on ordinary garden soil.
Propagating it
Seed is the only propagation method USDA lists. Division and cuttings are not listed as options. USDA records no cold-stratification requirement, so seed should germinate without a chilling period. Its seed spreads at a slow rate. It does not spread vegetatively, so it will stay where you put it.
Resilience and wildlife
Browsing animals rate it barely palatable — the sourced basis for calling it deer-resistant. Its fire tolerance is rated none. Its growth form is recorded as single crown.
Role in a guild
Nutrient layer. In a layered planting this is it contributes to soil fertility rather than to structure. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Crotalaria
- showy rattlebox Crotalaria spectabilis
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol CRJU, or is computed from those values by a fixed rule. Nothing here is estimated or model-generated. Where USDA publishes no value, this page omits the claim rather than filling the gap.
- Quoted from USDA PLANTS: active growth period, browse palatability, cold stratification, Drought tolerance, fall conspicuous, fertility requirement, fire tolerance, Flower color, flower conspicuous, foliage color, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Lifecycle, Light, Mature height, Minimum temperature, Native status, Nitrogen fixation, Nursery availability, precipitation max in, precipitation min in, propagation, resprout ability, root depth in, seed spread rate, Soil pH, Soil pH (upper), Tolerance of wet soil, Toxicity, Type, vegetative spread rate, Water need.
- Derived by a fixed rule from those columns: Guild layer.
Read our full data sources and methodology.
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