mammoth wildrye
Leymus racemosus · Poaceae
mammoth wildrye (Leymus racemosus) 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 3 and warmer, down to about -33°F.
At a glance
| Type | graminoid USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | introduced USDA |
| Mature height | 3 ft USDA |
| Light | full-sun USDA |
| Water need | medium USDA |
| Growth rate | rapid USDA |
| Soil pH | 6–9 USDA |
| Bloom | May–June USDA |
| Flower color | Yellow USDA |
| Hardiness zones | 3 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 moderate water needs. Its drought tolerance is rated high. It will not tolerate waterlogged soil — USDA rates its anaerobic tolerance as none. It is recorded on soils from pH 6 to 9 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 3.
Size and growth
At maturity it reaches about 3 ft, making it roughly waist to chest height. It grows quickly.
Bloom period
USDA records a bloom period of May through June. 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 active growth period is spring and summer. USDA rates its lifespan as moderate.
What the site needs to provide
USDA records it across sites receiving 10 to 60 inches of annual precipitation. The low end of that band is genuinely arid, so it has a wide tolerance for dry country. It needs at least 120 frost-free days to finish its season. It roots to at least 16 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 slow rate. It spreads vegetatively at a rapid rate.
Resilience and wildlife
Browsing animals rate it barely palatable — the sourced basis for calling it deer-resistant. Its fire tolerance is rated medium. 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 Leymus
- Altai wildrye Leymus angustus
- sand ryegrass Leymus arenarius
- basin wildrye Leymus cinereus
- giant wildrye Leymus condensatus
Similar role and hardiness
- common maidenhair Adiantum capillus-veneris
- winter bentgrass Agrostis hyemalis
- European water plantain Alisma plantago-aquatica
- showy milkweed Asclepias speciosa
- butterfly milkweed Asclepias tuberosa
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol LERA5, 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, 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, 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.
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