Large white trillium

Trillium grandiflorum

Iconic eastern North American spring ephemeral with large pure white three-petalled flowers above a whorl of three leaves. Emerges, flowers and goes dormant before the woodland canopy fully closes.

Hardiness ratings

Large white trillium hardiness across the four zone systems
SystemRatingTemperature rangeHow to read it
USDA hardiness zone Zone 4–8 −34.4 °C to −6.7 °C Plant tolerates down to this zone
RHS hardiness rating H6 −20 °C to −15 °C Plant needs at least this level of cold tolerance
Canadian plant hardiness zone Zone 4–7 −29 °C to −7 °C Plant tolerates down to this zone
Australian (ANBG) zone Zone 1–3 −15 °C to 0 °C Plant tolerates down to this zone

Growing notes

  • Flowers April–May, dies back by midsummer once the tree canopy closes overhead — a textbook spring ephemeral
  • Slow from seed — wild-dug plants once common in nurseries are now restricted, source only nursery-propagated stock
  • Provincial flower of Ontario, Canada
  • Needs deep humus-rich woodland soil and full deciduous shade in summer

Categories

Related plants

Cross-check Large white trillium against your zones

Reference

Large white trillium on Wikipedia