Bitter switchgrass 'Dewey Blue'
Panicum amarum 'Dewey Blue' · Poaceae
A wide fountain of intensely blue-grey leaves that arch to the ground, with airy, tan flower heads in late summer.
- Size
- 4 ft tall, 3 ft wide
- Zones
- 3 to 9
- Light
- Full sun
- Flowers
- Early August to early October
- Pets
- No toxicity recorded
- Job in a bed
- Drift
A bed built around bitter switchgrass 'Dewey Blue'
The planner designed this bed around bitter switchgrass 'Dewey Blue' when this page was made: a 12 × 6 ft (3.7 × 1.8 m) naturalistic planting in zone 6, full sun. It chose the other plants from the 715 that suit those conditions and its dry soil, and says below why bitter switchgrass 'Dewey Blue' stands where it does.
The plants
- 1 Bitter switchgrass 'Dewey Blue' × 1, tan
- 2 Woodland strawberry × 17, white
- 3 Cheddar pinks 'Firewitch' × 6, pink
- 4 Purple milkweed × 3, purple
- 5 Frikart's aster 'Monch' × 3, lavender
- 6 Lowbush blueberry × 3, white
- 7 Star of Persia × 3, purple
- 8 Broad-leaved grape hyacinth × 12, blue
Why this plant
- The only airy sprays. The others are open bowls, flat plates, daisies and others. Shape reads at a distance, where colours blur.
- 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 lowbush blueberry.
Why here
- Anchors a back corner. At 4 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 Frikart's aster 'Monch' (2½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- One plant, alone. A feature plant is seen as an object, and needs clear ground around it.
Why now
- In flower for 9 weeks. From early August to early October.
- In company. With woodland strawberry and Frikart's aster 'Monch' in early August: 3 kinds at once.
- 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 48% of the planted ground. The flowers stay on the cool side of the palette: pink, purple, lavender, blue, tan and white. The most in flower at one time is 4 kinds, from late May.
The planner's own design check: 11 Excellent, 6 Good. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where bitter switchgrass 'Dewey Blue' goes in a border
At 4 ft it belongs at the back of a bed. In the planner's ten height classes it is moderately tall (3 to 4 ft).
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
A grass of Atlantic sand dunes, so it takes salt, wind and the poorest, driest soil. The arching form is softer than the upright switchgrasses.
- Seaside gardens
- Blue foliage on dry, sandy soil
- Holding dunes and banks
What to plant with bitter switchgrass 'Dewey Blue'
Plants recorded as good partners for it, and what each pairing does:
- Northern bayberry: its dark green leaves are a setting for the flowers, before and after; tall enough (6½ ft) to stand behind it; happy in the same dry soil.
- Rugosa rose: in flower together for seven weeks, from early August; happy in the same dry soil.
- Sedum 'Autumn Joy': in flower together for eight weeks, from mid August; bold leaves against its fine ones; low enough (24 in) to stand in front of it.
Questions about bitter switchgrass 'Dewey Blue'
Does bitter switchgrass 'Dewey Blue' need sun or shade?
Bitter switchgrass 'Dewey Blue' grows in full sun (6 or more hours of direct sun a day).
It wants dry, sharply drained soil, on the lean side, with no feeding, and little watering once settled. Once settled in, it stands drought.
What zones does bitter switchgrass 'Dewey Blue' grow in?
USDA zones 3 to 9. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does bitter switchgrass 'Dewey Blue' 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 3 | Mid August to early October |
|---|---|
| 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 bitter switchgrass 'Dewey Blue' be planted?
2½ ft (75 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 3 ft (90 cm), so a group knits into one patch.
It grows 4 ft (120 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many bitter switchgrass 'Dewey Blue' plants do I need?
At 2½ ft apart, set out in staggered rows:
- 2 to fill 10 square feet (about 1 m²)
- 5 for a single row 10 ft (3 m) long
- 6 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 one in one group.
Is bitter switchgrass 'Dewey Blue' 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 bitter switchgrass 'Dewey Blue'?
They may. NC State does not list it as resistant to deer or rabbits. Where they visit, protect it, or plant it among ones they avoid.
What flowers after bitter switchgrass 'Dewey Blue'?
Bitter switchgrass 'Dewey Blue' is over by early October. These start as it finishes and carry the same spot on, so it never goes flat:
- Chrysanthemum 'Sheffield Pink': from late September to early November, 2½ ft tall, to stand in front of it and cover its fading stems.
- Tatarian aster 'Jindai': from early October to early November, 4 ft tall.
- Japanese onion 'Ozawa': from early October to early November, 10 in tall, to stand in front of it and cover its fading stems.
What does bitter switchgrass 'Dewey Blue' look like in winter?
Bitter switchgrass 'Dewey Blue' 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 bitter switchgrass 'Dewey Blue' good for bees and butterflies?
Bitter switchgrass 'Dewey Blue' is visited by pollinators, butterflies and 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
- 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 'Prairie Sky' Panicum virgatum 'Prairie Sky'
- Switchgrass 'Shenandoah' Panicum virgatum 'Shenandoah'
In these guides
- 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
- Silver and grey-leaved plants
- Host plants for the common wood-nymph
Zone guides: Zone 3 · Zone 4 · Zone 5 · Zone 6 · Zone 7 · Zone 8 · Zone 9
Every fact on record
- Type
- Grass
- Size
- 4 ft (120 cm) tall, 3 ft (90 cm) wide
- Plant
- 2½ ft (75 cm) apart
- Height class
- Moderately tall (3 to 4 ft)
- Place in the bed
- Back
- Flowers
- Early August to early October; airy sprays; tan
- Leaves
- Fine texture, herbaceous; blue-green, silver
- Shape
- Arching, clumping
- Hardy in
- USDA zones 3 to 9
- Light
- Full sun
- Soil
- Lean, dry and sharply drained
- Water
- Low
- Feeding
- None needed
- Family
- Poaceae
- Comes from
- Native to North America, Mexico
- Attracts
- Pollinators, butterflies, songbirds
- Host plant for
- Common wood-nymph
- Stands up to
- Drought, salt, black walnut, pollution, erosion
Checked against NC State Extension. 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.