Blue Oat Grass
Helictotrichon sempervirens
Blue Oat Grass blooms from June through July.
Mature size, hardiness zones, sun and the trait tags were checked against named botanical sources for this plant. The bloom months and water need on this page were not.
Growing Blue Oat Grass
Plant it in full sun. It prefers low water. It is hardy in USDA zones 4–9. Expect it to reach about 2.3 ft tall and 2 ft wide at maturity, in roughly 2 years.
When to plant Blue Oat Grass
Plant Blue Oat Grass in early spring as soon as the soil is workable, or in early fall at least six weeks before your first frost, so roots establish in cool weather. For the middle of its hardy zones 4 to 9 range, spring means March to May and fall means August or September. Once settled, it blooms from June to July.
Month-by-month timing for your zone is on the planting calendar: for the middle of its range, start with zone 6 in March.
Good to know about Blue Oat Grass
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
Worth knowing
Full sun does triple duty here: it deepens the steel-blue color, keeps the clump upright instead of floppy, and suppresses the foliar rust that takes hold in shade. per Illinois and Morton
Comb out, do not scalp
This evergreen grass resents hard shearing. Most sources comb or rake out the dead blades in spring; some instead trim to a few inches in late winter before new growth. per Wisconsin and Missouri Botanical
Zone range varies by source
Sources split on the cold floor (zone 3, 4, or 5) and warm ceiling (8 or 9). At the cold end, sharp winter drainage matters more than raw cold. per Wisconsin and Illinois
Clumps, never runs
A slow, tight bunch grass. It stays a discrete rounded tuft and spreads by no rhizomes or stolons, so it will not run into its neighbors. per Morton
Deer, rabbit, and drought resistant
Deer-resistant and rabbit-resistant, and rated drought-tolerant and tolerant of black walnut (juglone) and urban pollution. A dependable pick for low-water, xeric, and rock gardens. per North Carolina State
Wet soil is the killer
The main cause of death is crown and root rot in wet, poorly drained soil, worst over winter. The risk is overwatering, not drought; sharp drainage prevents it. per Missouri Botanical
What pairs well with Blue Oat Grass
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Basket of Gold
Shares full sun and low water; blooms in mid spring, before this one opens; lower at 8 in, for the front of the border; yellow sits close to orange on the wheel.
Creeping Phlox
Shares full sun and low water; blooms in mid spring, before this one opens; lower at 6 in, for the front of the border.
Lilac
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; taller at 9.8 ft, for the layer behind it; purple against orange, for contrast.
Monkshood
Takes full sun to part sun and low to moderate water; blooms in late summer as this one finishes; taller at 3.9 ft, for the layer behind it; blue against orange, for contrast.
Wisteria
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; blue against orange, for contrast.
Crocus
Shares full sun and low water; blooms in late winter, before this one opens; lower at 4 in, for the front of the border; purple against orange, for contrast.
Viburnum
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; taller at 6.6 ft, for the layer behind it; its white flowers settle the orange.
Grape Hyacinth
Shares full sun and low water; blooms in early spring, before this one opens; lower at 8 in, for the front of the border; blue against orange, for contrast.
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