Common Name: Switch Grass

General Information

Panicum virgatum is a perennial grass growing from a rhizomatous rootstock. The rhizomes are often loosely interwoven, sometimes short or forming a knotty crown. The culms range from 40 - 300cm tall, are 3 - 5 mm thick, sometimes solitary, at others forming dense erect or decumbent clumps[]
The plant is sometimes grown in soil stabilization schemes and is a potential source of biomass. There are several named forms, developed for their ornamental value[].
Panicum virgatum has a high risk of becoming a weed in any new area into which it is introduced[].

Known Hazards

None known

Botanical References

,

Range

North America - from southern Canada through the USA (excluding the west coast) and through Mexico to Honduras; Caribbean - Cuba

Habitat

Tallgrass prairies, especially mesic to wet types where it is a major component of the vegetation, and on dry slopes, sand, open oak or pine woodlands, shores, river banks, and brackish marshes[].

Properties

Weed Potential	Yes
Other Uses Rating
Habit	Perennial
Height	1.80 m
Pollinators	Wind
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Panicum virgatum is a plant, originally of the temperate zone, that has spread into the subtropics and tropics. It grows best in areas where annual daytime temperatures are within the range 17 - 32°c, but can tolerate 6 - 36°c[]. It can be killed by temperatures of -10°c or lower, though new growth can be damaged at -1°c[]. It prefers a mean annual rainfall in the range 500 - 1,100mm, but tolerates 350 - 2,700mm[].
Grows in any moderately fertile, well-drained soil in a sunny position[]. A drought resistant plant, it is easily grown in average to wet soils and in full sun to part shade[]. Prefers a pH in the range 6 - 7, tolerating 4.9 - 8.2[].
Plants have particularly heavy growth in late spring and early summer[].
The plant has the potential to produce the biomass required for production of up to 380 litres of ethanol per metric ton. This gives it the potential to produce over 400 litres of ethanol per hectare, compared to 270 for sugarcane and 160 for corn. However, there is debate on the viability of switchgrass, and other bio-fuels, as an efficient energy source. University of California, Berkeley professor Tad Patzek argues that switchgrass has a negative ethanol fuel energy balance, requiring 45% more fossil energy than the fuel produced[].
The plant photosynthesize by a more efficient method than most plants. Called the 'C4 carbon-fixation pathway', this process is particularly efficient at high temperatures, in bright sunlight and under dry conditions[].
As an open pollinated species, switchgrass expresses tremendous genetic diversity, with wide variations in its basic chromosome number (2n = 18), typically ranging from tetraploid to octoploid. Morphologically switchgrass in its southern range can grow to more than 3 m in height, but what is most distinctive is the deep, vigorous root system, which may extend to depths of more than 3.5 m[].. It reproduces both by seeds and vegetatively and, with its perennial life form, a stand can last indefinitely once established. Standing biomass in root systems may exceed that found aboveground, giving perennial grasses such as switchgrass, an advantage in water and nutrient acquisition even under stressful growing conditions[].

Edible Uses

None known

Medicinal

None known

Agroforestry Uses:

A valuable soil-stabilization plant, it is used as ground cover to control erosion[, ].
It can be used as an energy substitute and is often considered a good candidate for bio-fuel, especially ethanol fuel production, due to its hardiness against poor soil and climate conditions, rapid growth and low fertilization and herbicide requirements[, ].
The plant is sometimes used as a windbreak in crop fields[].

Other Uses

None known

Propagation

Seed - sow spring in a greenhouse and only just cover the seed. Germination should take place within a week. Prick out the seedlings into trays or individual pots and plant them out after the last expected frosts[, ].
Division in spring. Very easy, larger divisions can be planted out direct into their permanent positions. We have found that it is better to pot up the smaller divisions and grow them on in light shade in a cold frame until they are well established before planting them out in late spring or early summer.