Switchgrass
Panicum virgatum
also called panicum, switch grass
Lean soil and full sun are what hold it upright; anything richer or shadier and it sprawls into its neighbors.
- Type
- Grass · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Blue-green · Silver and gray
- Sunlight
- Full sun, six hours of direct light a day at the least.
- Watering
- Drought-tolerant once established; no regular watering needed.
- Feeding
- No feeding needed — lean soil gives the best form.
- Frost tolerant
- Yes
- Flowering
- July
- Pruning
- Cut back hard to 10–15 cm in late February or early March.
- Overwintering
- It looks after itself through winter, with no protection needed.
- Apr–Jul Spring Growth
- Jul–Oct Flowering
- Oct–Nov Growing
- Nov–Dec Leaf Fall
- Jan–Apr Leaf Fall
- Plant spacing
- 23.6 in
- In-row spacing
- 23.6 in
- Between rows
- 2 ft 6 in
- Square-foot density
- Not suited to SFG
- Root system
- A dense fibrous mat
- Working depth
- 24 in–6.5 ft
- Can reach
- 10 ft down where the soil allows
- Spread
- 24 in–4 ft across, about 1–2× the width of the plant
- Shallowest pot
- 12 in of soil
Thousands of fine roots knit the top of the soil into a turf, which is what holds a bank together and what makes an established clump so hard to lift. Prairie grasses send a few roots far below the mat as well.
Switchgrass roots go down three metres in good ground, which is why it is used to stabilise banks and rebuild worn-out soil, and why an established clump never needs watering.
Figures recorded for Switchgrass itself. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
Grasses, like this one.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com