Northern sea oats 'River Mist'
Chasmanthium latifolium 'River Mist' · Poaceae
Bamboo-like leaves boldly striped in white and green, with the same dangling, flat, oat-like seed heads as the species.
- Size
- 2½ ft tall, 24 in wide
- Zones
- 5 to 9
- Light
- Part sun to part shade
- Flowers
- Late July to mid September
- Pets
- No toxicity recorded
- Job in a bed
- Drift
A bed built around northern sea oats 'River Mist'
The planner designed this bed around northern sea oats 'River Mist' when this page was made: a 12 × 6 ft (3.7 × 1.8 m) naturalistic planting in zone 6, part sun. It chose the other plants from the 708 that suit those conditions, and says below why northern sea oats 'River Mist' stands where it does.
The plants
- 1 Northern sea oats 'River Mist' × 3, green
- 2 Bloody cranesbill × 4, pink
- 3 Stemless gentian × 24, blue
- 4 Swamp milkweed 'Ice Ballet' × 3, white
- 5 Globe arborvitae 'Danica' × 1, green leaves
- 6 Black-eyed Susan × 3, yellow
- 7 Grecian windflower × 7, blue
- 8 Easter lily × 3, white
Why this plant
- Part of the matrix. The low fabric of grasses and groundcovers that the taller plants come up through.
- The only airy sprays. The others are open bowls, trumpets, flat plates and others. Shape reads at a distance, where colours blur.
- The only green. Green sits between stronger colours and calms them.
Why here
- At the back. At 2½ ft it is seen over globe arborvitae 'Danica' (24 in) in front of it, and has nothing behind it to hide.
- A step in the back row. Next to swamp milkweed 'Ice Ballet' (3½ ft) and Easter lily (3 ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 3 plants in one group. Massed, one kind reads as a single shape. Scattered, it would look spotty.
Why now
- In flower for 9 weeks. From late July to mid September.
- Part of the bed's peak. With bloody cranesbill, swamp milkweed 'Ice Ballet' and black-eyed Susan in late July: 4 kinds at once. No week has more.
- Stands through winter. Left uncut, it holds its shape until March, when the perennials have gone.
Planned as a naturalistic planting: low grasses and groundcovers, the matrix, make up 47% of the planted ground. The back corners are held by swamp milkweed 'Ice Ballet' and Easter lily, the tallest plants on the plan. The scheme leans cool (pink and blue) and uses yellow for warmth, with green and white to calm things between them.
The planner's own design check: 10 Excellent, 7 Good.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where northern sea oats 'River Mist' goes in a border
At 2½ ft it belongs in the middle of a bed. In the planner's ten height classes it is medium (24 in to 2½ ft).
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
The variegation lights up part shade, and unlike the green species it seeds very little. The seed heads tremble in the slightest wind.
- Variegated foliage in part shade
- Seed heads for movement
- Woodland edges
What to plant with northern sea oats 'River Mist'
Plants recorded as good partners for it, and what each pairing does:
- Hosta 'Halcyon': its blue-green leaves are a setting for the flowers, before and after; bold leaves against its medium ones; low enough (18 in) to stand in front of it.
- Japanese anemone: in flower together for six weeks, from mid August; happy in the same moist soil.
- Astilbe: flowers first, late June to mid July, so the spot is never empty; happy in the same moist soil.
Questions about northern sea oats 'River Mist'
Does northern sea oats 'River Mist' need sun or shade?
Northern sea oats 'River Mist' grows in part sun (4 to 6 hours of sun, including some afternoon sun) and part shade (2 to 4 hours of sun, mostly in the morning).
It wants soil that stays evenly moist, of average fertility, and a good soak in dry spells. Once settled in, it stands drought.
What zones does northern sea oats 'River Mist' grow in?
USDA zones 5 to 9. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does northern sea oats 'River Mist' flower in my zone?
In zone 5 it flowers late July to mid September. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 5 | Late July to mid September |
|---|---|
| Zone 6 | Late July to mid September |
| Zone 7 | Mid July to mid September |
| Zone 8 | Mid July to mid September |
| Zone 9 | Mid July to mid September |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should northern sea oats 'River Mist' be planted?
20 in (50 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 24 in (60 cm), so a group knits into one patch.
It grows 2½ ft (75 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many northern sea oats 'River Mist' plants do I need?
At 20 in apart, set out in staggered rows:
- 4 to fill 10 square feet (about 1 m²)
- 7 for a single row 10 ft (3 m) long
- 14 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as a group of three or five, with a second group further along in the other number.
In the bed above, the planner used three in one group.
Is northern sea oats 'River Mist' poisonous to dogs and cats?
No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension.
"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.
Do deer eat northern sea oats 'River Mist'?
Mostly not. NC State lists it as resistant to deer. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
What flowers after northern sea oats 'River Mist'?
Northern sea oats 'River Mist' is over by mid September. These start as it finishes and carry the same spot on, so it never goes flat:
- Toad lily: from mid September to mid October, 2½ ft tall.
- Blue wood aster: from mid September to mid October, 3 ft tall.
- October daphne: from mid September to late October, 8 in tall, to stand in front of it and cover its fading stems.
What does northern sea oats 'River Mist' look like in winter?
Northern sea oats 'River Mist' turns the colour of straw and, left uncut, stands through the winter, with seed for the birds. Cut it down in late winter, before the new shoots come up.
Is northern sea oats 'River Mist' good for bees and butterflies?
Northern sea oats 'River Mist' is visited by pollinators, butterflies and songbirds.
It is a host plant: the caterpillars of northern pearly-eye feed on its leaves. A butterfly can only lay its eggs on its host plants, so these do more for it than any nectar flower.
It is native to the United States (this is a named variety of the native plant).
More Chasmanthium
- Northern sea oats Chasmanthium latifolium
In these guides
- Plants for dry shade
- Plants for wet soil and rain gardens
- Salt-tolerant plants for roadsides and coasts
- Plants that grow near black walnut
- Plants for slopes and banks
- Deer-resistant plants for shade
- Pet-safe plants for shade
- Native plants for shade
- Plants for butterflies
- Plants that feed garden birds
- Ornamental grasses under 3 feet
- Host plants for the northern pearly-eye
Every fact on record
- Type
- Grass
- Size
- 2½ ft (75 cm) tall, 24 in (60 cm) wide
- Plant
- 20 in (50 cm) apart
- Height class
- Medium (24 in to 2½ ft)
- Place in the bed
- Middle
- Flowers
- Late July to mid September; airy sprays; green, tan
- Leaves
- Medium texture, herbaceous; variegated
- Shape
- Arching, clumping
- Hardy in
- USDA zones 5 to 9
- Light
- Part sun, part shade
- Soil
- Average, evenly moist
- Water
- Moderate
- Feeding
- None needed
- Family
- Poaceae
- Comes from
- Central Canada, Central & E. U.S.A. to NE. Mexico
- Attracts
- Pollinators, butterflies, songbirds
- Host plant for
- Northern pearly-eye
- Stands up to
- Deer, drought, salt, wet soil, black walnut, erosion
Checked against NC State Extension and VASCAN (plants of Canada). Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.