toughleaf iris
Iris tenax · Iridaceae
toughleaf iris (Iris tenax) is a perennial herbaceous plant in the Iridaceae family. It is native to North America. USDA records it as hardy in zone 5 and warmer, down to about -13°F.
At a glance
| Type | forb-herb USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | native USDA |
| Mature height | 1.5 ft USDA |
| Light | shade USDA |
| Water need | medium USDA |
| Growth rate | moderate USDA |
| Soil pH | 6–8 USDA |
| Bloom | April–May USDA |
| Flower color | Purple USDA |
| Hardiness zones | 5 and warmer USDA |
| Guild layer | ground-cover Derived |
| Nursery availability | Contracting Only 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 tolerates full shade. USDA rates it as having moderate water needs. Its drought tolerance is rated medium. It handles periodically wet ground (USDA rates its anaerobic tolerance medium). It is recorded on soils from pH 6 to 8 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 5.
Size and growth
At maturity it reaches about 1.5 ft, making it about knee height. It grows at a moderate rate.
Bloom period
USDA records a bloom period of April through May. Flowers are purple.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is yellow-green, medium in texture. Its flowers are conspicuous. 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 16 to 60 inches of annual precipitation. It needs at least 120 frost-free days to finish its season. It roots to at least 12 inches. Fertility requirement: medium.
Propagating it
Propagate it from seed and bulbs. 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 slow rate.
Resilience and wildlife
Its fire tolerance is rated low. Its growth form is recorded as rhizomatous.
Role in a guild
Ground cover. In a layered planting this is the lowest layer — it shades soil, holds moisture, and suppresses weeds. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Iris
- Siskiyou iris Iris bracteata
- copper iris Iris fulva
- Rocky Mountain iris Iris missouriensis
- Virginia iris Iris virginica
Similar role and hardiness
- pinemat manzanita Arctostaphylos nevadensis
- winter creeper Euonymus fortunei
- boraxweed Nitrophila occidentalis
- knotgrass Paspalum distichum
- spreading phlox Phlox diffusa
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol IRTE, 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, 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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