Switchgrass 'Prairie Sky'
Panicum virgatum 'Prairie Sky' · Poaceae
The bluest switchgrass: powder-blue leaves on an upright clump, topped with a pale haze of flowers in late summer, then yellow in autumn.
- Size
- 5 ft tall, 2½ ft wide
- Zones
- 4 to 9
- Light
- Full sun
- Flowers
- Early August to early October
- Pets
- No toxicity recorded
- Job in a bed
- Drift
A bed built around switchgrass 'Prairie Sky'
The planner designed this bed around switchgrass 'Prairie Sky' when this page was made: a 12 × 6 ft (3.7 × 1.8 m) contemporary bed in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why switchgrass 'Prairie Sky' stands where it does.
The plants
- 1 Switchgrass 'Prairie Sky' × 4, tan
- 2 Coral bells 'Firefly' × 8, red
- 3 Creeping phlox × 3, pink
- 4 False sunflower 'Summer Sun' × 3, yellow
- 5 Globe arborvitae 'Danica' × 1, green leaves
- 6 Japanese aster 'Blue Star' × 3, lavender
- 7 Madonna lily × 1, white
Why this plant
- The only tan. Tan sits between stronger colours and calms them.
- Part of the bed's structure. Shrubs and grasses keep their shape when the perennials die down. So does globe arborvitae 'Danica'.
Why here
- Anchors a back corner. At 5 ft it is the tallest plant here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to madonna lily (4 ft) and false sunflower 'Summer Sun' (3½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 4 plants in 2 groups (3 and 1). Seen again further along, the same plant ties the bed together.
Why now
- In flower for 9 weeks. From early August to early October.
- Closes the season. For its last two weeks nothing else on the plan is in flower.
- Stands through winter. Left uncut, it holds its shape until March, when the perennials have gone.
Planned as a contemporary bed: 20 of the 20 plants that stand in groups (100%) are set out in a pattern with their neighbours: a straight row, a triangle, or five like the five on a dice. The back corners are held by switchgrass 'Prairie Sky' and false sunflower 'Summer Sun', the tallest plants on the plan. Switchgrass 'Prairie Sky' repeats along the bed to tie it together.
The planner's own design check: 9 Excellent, 6 Good, 1 Satisfactory.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where switchgrass 'Prairie Sky' goes in a border
At 5 ft it belongs at the back of a bed. In the planner's ten height classes it is tall (4 to 5 ft). It is airy enough to see through, so it can also come forward and veil what is behind it.
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
Bluer than 'Heavy Metal'. It can lean in rich soil or shade, so grow it lean and in full sun.
- Blue foliage at the back
- Prairie planting
- Winter structure
What to plant with switchgrass 'Prairie Sky'
Plants recorded as good partners for it, and what each pairing does:
- Purple coneflower: in flower together for five weeks, from early August; low enough (3 ft) to stand in front of it.
- Black-eyed Susan: in flower together for seven weeks, from early August; low enough (24 in) to stand in front of it.
- Aromatic aster 'October Skies': in flower together for three weeks, from mid September; low enough (20 in) to stand in front of it.
Questions about switchgrass 'Prairie Sky'
Does switchgrass 'Prairie Sky' need sun or shade?
Switchgrass 'Prairie Sky' grows in full sun (6 or more hours of direct sun a day).
It wants ordinary well-drained soil, of average fertility, and little watering once settled. Once settled in, it stands drought.
What zones does switchgrass 'Prairie Sky' grow in?
USDA zones 4 to 9. It is hardy to zone 4, which means it survives winter nights down to about −20 °F (−29 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does switchgrass 'Prairie Sky' flower in my zone?
In zone 5 it flowers early August to early October. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 4 | Mid August to early October |
|---|---|
| Zone 5 | Early August to early October |
| Zone 6 | Early August to early October |
| Zone 7 | Early August to early October |
| Zone 8 | Early August to early October |
| Zone 9 | Late July to early October |
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 switchgrass 'Prairie Sky' be planted?
24 in (60 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 2½ ft (75 cm), so a group knits into one patch.
It grows 5 ft (150 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many switchgrass 'Prairie Sky' plants do I need?
At 24 in apart, set out in staggered rows:
- 3 to fill 10 square feet (about 1 m²)
- 6 for a single row 10 ft (3 m) long
- 10 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 four in two groups.
Is switchgrass 'Prairie Sky' 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 switchgrass 'Prairie Sky'?
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 switchgrass 'Prairie Sky'?
Switchgrass 'Prairie Sky' is over by early October. These start as it finishes and carry the same spot on, so it never goes flat:
- Tatarian aster 'Jindai': from early October to early November, 4 ft tall.
- Chrysanthemum 'Sheffield Pink': from late September to early November, 2½ ft tall, to stand in front of it and cover its fading stems.
- Swamp sunflower: from late September to late October, 6½ ft tall.
What does switchgrass 'Prairie Sky' look like in winter?
Switchgrass 'Prairie Sky' 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 switchgrass 'Prairie Sky' good for bees and butterflies?
Switchgrass 'Prairie Sky' is visited by songbirds.
It is a host plant: the caterpillars of common wood-nymph 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 and Canada (this is a named variety of the native plant).
More Panicum
- Bitter switchgrass 'Dewey Blue' Panicum amarum 'Dewey Blue'
- Switchgrass 'Cheyenne Sky' Panicum virgatum 'Cheyenne Sky'
- Switchgrass 'Cloud Nine' Panicum virgatum 'Cloud Nine'
- Switchgrass 'Heavy Metal' Panicum virgatum 'Heavy Metal'
- Switchgrass 'Northwind' Panicum virgatum 'Northwind'
- Switchgrass 'Shenandoah' Panicum virgatum 'Shenandoah'
In these guides
- 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
- Pet-safe plants for a sunny border
- Garden plants native to Canada
- Plants for butterflies
- Plants that feed garden birds
- Tall perennials and grasses for the back of a border
- Host plants for the common wood-nymph
Zone guides: Zone 4 · Zone 5 · Zone 6 · Zone 7 · Zone 8 · Zone 9
Every fact on record
- Type
- Grass
- Size
- 5 ft (150 cm) tall, 2½ ft (75 cm) wide
- Plant
- 24 in (60 cm) apart
- Height class
- Tall (4 to 5 ft)
- Place in the bed
- Back, or further forward: it is airy enough to see through
- Flowers
- Early August to early October; airy sprays; tan
- Leaves
- Fine texture, herbaceous; blue-green
- Shape
- Upright, clumping
- Hardy in
- USDA zones 4 to 9
- Light
- Full sun
- Soil
- Average, well-drained
- Water
- Low
- Feeding
- None needed
- Family
- Poaceae
- Comes from
- North America
- Attracts
- Songbirds
- Host plant for
- Common wood-nymph
- Stands up to
- Deer, drought, salt, wet soil, black walnut, pollution, 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.