Let’s complete this autumn series on ornamental grasses with this last one that is also among my favorites. Native to the tall prairies of North America, switchgrass (Panicum virgatum) has created in its wake a panoply of horticultural varieties, each more interesting than the last.

This tall or medium-sized grass is mainly defined by its light flowering. In large clumps, panicles form a sort of rounded cloud that spreads above the foliage. The flowering is in reality a very branched panicle where the small rounded spikelets appear as scattered dots. Depending on the cultivar, the flowering takes on different shades ranging from steel blue to beige to pink to purple. At the end of the season, the seeds nourish many granivorous birds.
Foliage for All!
The other strong feature of these grasses is their foliage. There is a whole variation in color between the young leaves of spring, the more assertive colors of summer and the often-flamboyant tones of autumn. It’s worth noting that switchgrass begin their growth a little later in the spring than other ornamental grasses.
In terms of summer foliage color, there is switchgrass with very pronounced steel gray foliage, such as the ‘Heavy Metal’ variety. And, at the other end of the spectrum, there are cultivars with foliage almost as black as that of the Andropogon ‘Blackhawks’. This is the case of the panic grass ‘Blood Brothers’. Then in between, there is a whole range of foliage with shoots tinged with red, purple or burgundy. These last varieties make excellent substitutes for red grass (Imperata cylindrica ‘Red Baron’). Red grass is a favorite among red-leaved grasses, but it is a disappointment in the garden due to its poor performance. This is not the case with switchgrass.

Its Integration in Landscape Design
In general, switchgrass is more interesting in small groups than isolated. Indeed, in some varieties, the foliage tends to droop. This is often caused by the the excess of fertilization. That makes the stems more flexible or when exposed to strong gusts of wind. Thus grouped in small clusters of three or more plants or even planted in large masses of several dozen specimens, switchgrass create a striking effect.

The rather rounded shape of certain cultivars contrasts perfectly with the upright appearance of bluestems (Andropognons spp. and Schizachyrium spp.), Calamagrostis (Calamagrostis spp.) or Chinese miscanthus (Miscanhtus sinensis). This means that switchgrass fit very well into arrangements mainly composed of ornamental grasses.
Switchgrass also makes a beautiful low hedge and can fill the space along a sunny wall. In fact, one of the most beautiful combinations I have ever seen is a simple duo of herbaceous peonies and switchgrass. The peonies beautify the early summer. Then the switchgrass buries the peony foliage to become the center of interest in summer and fall.

The varieties with wine red and purple highlights work wonders alongside the pink coneflowers (Echinacea spp.), blue balls (Echinops spp.), bee balm (Monarda spp.) and blazing stars (Liatris spp.), shrub roses (Rosa spp.) and smoke bush (Cotinus spp.).

Sun and Freshness
In its natural environment, native switchgrass grows in sunny locations and in relatively cool, even slightly moist soil. The same is true for cultivars. Full sun is an absolute prerequisite. Switchgrass becomes sparse if grown in shade. As for the soil, it must be said that switchgrass tolerates drought and dry soils well. However, it’s in loose, cool soils that it’s most at ease. A thick layer of mulch at the base of the plants is beneficial to switchgrass.
This ornamental grass develops by short rhizomes, which makes its growth very reasonable. Switchgrass is not recognized as an invasive plant. Also, few spontaneous seedlings have been observed in cultivars.
They are best planted in rather poor soils, because too much fertilizer makes them less solid. A simple application of compost every two years is quite sufficient.
Like most grasses, we tend to leave the foliage in place for the fall and winter. This way, we enjoy the beautiful colors of the leaves. It’s only in spring that we cut the plant back to 10 or 15 cm (about 6 inches) from the ground. If the plants seem less structured or if we want to move it to a sunnier location, it’s also in spring that we can proceed.
In general, all switchgrass is perfectly hardy in USDA zones 3 to 9.

Some Interesting Varieties for Gardens
‘Apache Rose’ : H.: 120 cm (4 feet); W.: 75 cm (2 ½ feet); Foliage in summer: bluish; Foliage in autumn: purple-pink leaf tips. Purplish-pink flowering.
‘Blood Brothers’ : H.: 125 cm (4 feet); W.: 90 cm (3 feet); Foliage in summer: dark red, almost black; Foliage in autumn: red. This is the panic with the darkest foliage currently in cultivation.
‘Blue Fountain’ : H.: 200 cm (6 ½ feet); W.: 175 cm (5 ¾ feet); Foliage in summer: steel blue; Foliage in autumn: straw yellow.
‘Cheyenne Sky’ : H.: 90 cm (3 feet); W.: 45 cm (1 ½ foot); Summer foliage: blue-green with wine-red shoots; Autumn foliage: dark red.
‘Heavy Metal’ : H.: 150 cm (5 feet); W.: 90 cm (3 feet); Foliage in summer: steel gray; Foliage in autumn: golden with beautiful orange highlights.
‘Hot Rod’ : H.: 120 cm (4 feet); W.: 90 cm (3 feet); Summer foliage: wine-red shoots; Autumn foliage: dark purple red.
‘Niagara Falls’ : H.: 120 cm (4 feet); W.: 120 cm (4 feet), Summer foliage: steel blue; Autumn foliage: straw yellow.
‘Northwind’ : H.: 150 cm (5 feet); W.: 90 cm (3 feet); Summer foliage: bluish; Autumn foliage: a mixture of chartreuse green, gold and orange highlights. Variety with an upright habit.
‘Prairie Fire’ : H.: 150 cm (5 feet); W.: 60 cm (2 feet); Foliage in summer: green with lots of dark red; Foliage in autumn: dark red turning butter yellow.
‘Prairie Sky’ : H.: 125 cm (4 feet); W.: 60 cm (2 feet); Summer foliage: steel blue; Autumn foliage: golden with brown highlights.
‘Shenandoah’ : H.: 120 cm (4 feet); W.: 120 cm (4 feet), Foliage in summer: bluish with red shoots; Foliage in autumn: wine red.
‘Totem Pole’ : H.: 180 cm (5 ¾ feet); W.: 75 cm (2 ½ feet); Foliage in summer: gray-green; Foliage in autumn: straw yellow. Plant with a more upright shape.
Now that this “grass special” is over, I would be very curious to know what is your favorite ornamental grass, between bluestem (Andropogon spp.), moor grass (Molinia spp.) and switchgrass (Panicum spp.)? Which grasses grow well in your gardens? What are your favorites and your rants?

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I have only variegated moor grass, but have looked at a number bluestem grasses, particularly those with interesting colours. Thanks for the list!