Switchgrass 'Heavy Metal'
Panicum virgatum 'Heavy Metal' · Poaceae
Stiffly upright, metallic blue leaves topped with a fine haze of pink flowers in late summer. It turns yellow in autumn.
- Size
- 4½ ft tall, 24 in wide
- Zones
- 4 to 9
- Light
- Full sun
- Flowers
- Late July to mid September
- Pets
- No toxicity recorded
- Job in a bed
- Accent
A bed built around switchgrass 'Heavy Metal'
The planner designed this bed around switchgrass 'Heavy Metal' 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 'Heavy Metal' stands where it does.
The plants
- 1 Switchgrass 'Heavy Metal' × 3, pink
- 2 Mountain sandwort × 8, white
- 3 Mouse-ear coreopsis 'Nana' × 11, yellow
- 4 False sunflower 'Summer Sun' × 3, yellow
- 5 Globe arborvitae 'Danica' × 1, green leaves
- 6 Oriental poppy 'Patty's Plum' × 3, purple
Why this plant
- The only airy sprays. The others are open bowls and daisies. Shape reads at a distance, where colours blur.
- The only pink.
- 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 4½ 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 oriental poppy 'Patty's Plum' (2½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 3 plants in one clump. A single spire is too slight to hold a place alone, so here the accent is a clump.
Why now
- In flower for 9 weeks. From late July to mid September.
- 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: 28 of the 28 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. Cool colours (pink and purple) set against hot ones (yellow), with white to calm things between them. The back corners are held by switchgrass 'Heavy Metal' and false sunflower 'Summer Sun', the tallest plants on the plan.
The planner's own design check: 9 Excellent, 7 Good, 1 Satisfactory. 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 switchgrass 'Heavy Metal' goes in a border
At 4½ 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: accent. An upright plant used singly, like a punctuation mark, and repeated at intervals to give the bed rhythm.
The bluest of the switchgrasses. The cloud of flowers above is transparent, so the plant reads as a blue column with a pink mist over it.
- Blue foliage with an airy pink top
- Vertical accents
- Dry or moist soil
What to plant with switchgrass 'Heavy Metal'
Plants recorded as good partners for it, and what each pairing does:
- Russian sage: in flower together for eight weeks, from late July.
- Sedum 'Autumn Joy': in flower together for six weeks, from mid August; bold leaves against its fine ones; low enough (24 in) to stand in front of it.
- Black-eyed Susan: in flower together for nine weeks, from late July; low enough (24 in) to stand in front of it.
Questions about switchgrass 'Heavy Metal'
Does switchgrass 'Heavy Metal' need sun or shade?
Switchgrass 'Heavy Metal' 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 'Heavy Metal' 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 'Heavy Metal' 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 4 | Early August to mid September |
|---|---|
| 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 switchgrass 'Heavy Metal' be planted?
24 in (60 cm) apart, from the middle of one plant to the middle of the next. That is about its full width, so each plant keeps its own outline.
It grows 4½ ft (140 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many switchgrass 'Heavy Metal' 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 one at a time, repeated along the bed at intervals; a slender one reads better as a clump of three.
In the bed above, the planner used three in one group.
Is switchgrass 'Heavy Metal' 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 'Heavy Metal'?
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 'Heavy Metal'?
Switchgrass 'Heavy Metal' is over by mid September. These start as it finishes and carry the same spot on, so it never goes flat:
- Garden chrysanthemum: from mid September to late October, 24 in tall, to stand in front of it and cover its fading stems.
- Montauk daisy: from mid September to late October, 3 ft tall, to stand in front of it and cover its fading stems.
- Calico aster 'Lady in Black': from mid September to mid October, 3½ ft tall, to stand in front of it and cover its fading stems.
What does switchgrass 'Heavy Metal' look like in winter?
Switchgrass 'Heavy Metal' 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 'Heavy Metal' good for bees and butterflies?
Switchgrass 'Heavy Metal' 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 'Northwind' Panicum virgatum 'Northwind'
- Switchgrass 'Prairie Sky' Panicum virgatum 'Prairie Sky'
- 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
- 4½ ft (140 cm) tall, 24 in (60 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
- Late July to mid September; airy sprays; pink
- 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. 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.