Johnsongrass
Sorghum halepense · Poaceae
Johnsongrass (Sorghum halepense) is a perennial grass or grass-like plant in the Poaceae family. It is introduced to North America rather than native. USDA records it as hardy in zone 5 and warmer, down to about -13°F.
⚠ Invasive or noxious status. USDA lists this plant with an invasive or noxious weed status somewhere in its range. Check your state's noxious weed list before planting it — in some states it is illegal to sell or plant.
⚠ Allelopathic. USDA flags this plant as releasing compounds that can suppress the growth of plants near it. Give neighbours extra room, and expect some companions to struggle regardless of how well their conditions match.
Both flags are quoted from USDA PLANTS, not inferred.
At a glance
| Type | graminoid USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | introduced USDA |
| Mature height | 3.5 ft USDA |
| Light | full-sun USDA |
| Water need | high USDA |
| Growth rate | rapid USDA |
| Soil pH | 5–7 USDA |
| Bloom | August–September USDA |
| Flower color | Yellow USDA |
| Hardiness zones | 5 and warmer USDA |
| Guild layer | herb-layer 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 low. It is recorded on soils from pH 5 to 7 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 5.
Size and growth
At maturity it reaches about 3.5 ft, making it roughly waist to chest height. It grows quickly.
Bloom period
USDA records a bloom period of August through September. Flowers are yellow.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is green, coarse in texture. Its flowers are not conspicuous — a plant for form and foliage. Its fruit or seed heads are conspicuous, extending interest past flowering. Its active growth period is summer and fall. USDA rates its lifespan as long.
What the site needs to provide
USDA records it across sites receiving 32 to 60 inches of annual precipitation. It needs at least 165 frost-free days to finish its season. It roots to at least 10 inches. Fertility requirement: medium.
Propagating it
Propagate it from seed and sprigs. USDA records no cold-stratification requirement, so seed should germinate without a chilling period. Its seed spreads at a rapid rate. It spreads vegetatively at a rapid rate.
Resilience and wildlife
Browsing animals find it highly palatable, so expect deer and rabbits to take an interest. Its fire tolerance is rated high. Its growth form is recorded as rhizomatous.
Role in a guild
Herb layer. In a layered planting this is the herbaceous middle — perennials and grasses that fill the space between ground cover and shrubs. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Sorghum
- sorghum Sorghum bicolor
- grain sorghum Sorghum bicolor
- Sudangrass Sorghum bicolor
Similar role and hardiness
- field mustard Brassica rapa
- white edge sedge Carex debilis
- blue mistflower Conoclinium coelestinum
- sticky purple geranium Geranium viscosissimum
- green sprangletop Leptochloa dubia
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol SOHA, 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, Allelopathy, Bloom, Bloom end, browse palatability, cold stratification, Drought tolerance, fall conspicuous, fertility requirement, fire tolerance, Flower color, flower conspicuous, foliage color, foliage porosity winter, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Invasive status, Lifecycle, lifespan, 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.
Find more plants for your zone with the Plant Finder.