Northern Sea Oats

Chasmanthium latifolium

Poaceae · grass sedge · introduced

Last updated March 8, 2026

Data Coverage 2 of 6 dimensions

Site Data

Threats

Cultivars

Phenology

GDD Thresholds

Puget Sound

Quick Facts

Height

5 ft

Growth Rate

Moderate

Light

Part Shade

Soil

Wet Tolerant

Water

Moderate

Hardiness

Zone Zones 4a–9b

Bloom Time

August to September

Stage	Typical Window	What to Look For
Bud break BBCH 07	Feb 15-Mar 15	Buds swelling and beginning to open; first green tissue visible
Leaf emergence BBCH 11	Mar 1-Apr 1	First leaves fully unfurled on new growth
Bloom start BBCH 61	Jun 15-Aug 15	First open flowers visible; flowers green
Bloom end / petal fall BBCH 69	Jul 15-Aug 31	Last petals falling; flower structures fading
Fruit/seed development BBCH 71	Jun 1-Aug 31	Fruit or seed structures forming; fruit color: black
Fruit/seed maturity BBCH 85	Sep 1-Nov 30	Fruit fully colored and ripened; seed dispersal may begin
Leaf drop BBCH 93	Oct 15-Nov 30	Leaves yellowing and dropping; no significant fall color display
Dormancy BBCH 97	Nov 15-Feb 28	Leafless; no active growth; dormant buds set