Grasses for Garden Interest
Posted: July 31, 2012
By Pauline Myers, PSU Montgomery County Master Gardener
Grasses are not just turf...or weeds.
Ornamental grasses offer plenty of options that can add drama and movement to the garden, act as focal points, give multi-season interest and solve tough landscaping problems. These actually include three different families: true grasses, sedges and rushes. All have grass-like leaves, but that’s where the similarity ends. There is an ornamental grass adapted to nearly any growing condition, from wet to dry and sun to shade. They come in all sizes from small to tall and in various habits including carpet forming, mounding and fountain-like. They can be green, yellow, bluish, reddish, brown or variegated. And they require minimal maintenance!
As with all plants, ornamental grasses need to be matched to site conditions and they will need to be watered during their first year in your garden. In spring, the tall grasses should be cut back to 4 – 6 inches and the short grasses may need to be mowed or to have dead leaves removed. Tall grasses that are not wanted for winter interest or not in suitable condition may be cut back in fall or winter. If you fertilize, use a balanced formula such as 10-10-10. High nitrogen formulations (those with a larger first number) cause lush growth, which cannot support itself and falls over. Don’t plant tall grasses near buildings; the dry grass is a fire hazard.
Perennial ornamental grasses are either clump-formers or runners. The clump-formers stay where you plant them and just increase in diameter over time. These are good in beds and borders or as a focal point. The runners spread rapidly by means of below ground structures called rhizomes or above ground structures called stolons. These are good as ground covers in difficult areas or grown in containers. It’s important to be aware of these growth habits so you don’t end up with a “thug” taking over your garden.
Here are some possibilities to consider for your garden from the more than 10,000 species of grasses and more than 3,000 species of sedges:
Sedges range from 6” to 2ft, with most around 12”. They are both shade and moisture tolerant and make good groundcovers. They provide both texture and color interest with blades ranging from narrow to wide and colors from green (Pennsylvania sedge – Carex pennsylvanica) to yellow (Bowles’ golden sedge – Carex elata ‘Aurea’) to variegated (striped sedge - Carex morrowii ‘Variegata’).
Greater woodrush (Luzula sylvatica) grows to 12” with broad green leaves, or yellow-green in the cultivar ‘Aurea’. It prefers moisture, but it will tolerate drought once established.
Blue oat grass (Helictotrichon sempervirens), at 12 – 18”, is a sun tolerant groundcover with blue foliage.
Accents Tall and Small
Giant miscanthus (Miscanthus floridulus ’Giganteus’) is a great tall accent, reaching 8 – 12ft. Other Miscanthus include morning light grass (Miscanthus sinensis ‘Morning Light’) which is green and white, growing to 3 – 4ft and Zebra grass (Miscanthus sinensis ‘Zebrinus’) which is green with yellow bands, growing to 7ft. All have a fountain shape and burgundy-tinged flower plumes in late summer. Note: Miscanthus blades have sharp edges that cut as sharply as a razor blade. Do not place them where people will brush against them and wear gloves when working around them.
Elijah blue fescue (Festuca glauca ‘Elijah blue’) forms 6 – 10” bluish mounds that are great mixed into beds, used as edging and even in containers. It will tolerate hot, dry sites once established.
Karl Foerster feather reed grass (Calamagrostis x acutiflora ‘Karl Foerster’) grows to four – six feet, with tan-gold flowers in summer.
Switchgrass (Panicum virgatum ‘Heavy Metal’,‘Dallas Blues’ and other cultivars) grows three – six feet with airy pinkish to silvery flowers creating a cloud-like effect mid to late summer.
Hakone grass (Hakonechloa macra) forms 12” flowing masses of exceptional beauty. The cultivar ‘Aureola’ has golden variegation. It grows in shade and will tolerate drought once established.
Mexican feather grass (Nasella tenuissima, Stipa tenuissima) is finely textured, growing to 18”. It looks just as great in containers as it does in the garden and tolerates hot, dry conditions.
Fall & Winter Interest
Ornamental grasses don’t have showy flowers like herbaceous perennials do, but their seed pods have interesting shapes and provide fall and winter interest in the garden:
Karl Foerster feather reed grass (Calamagrostis x acutiflora ‘Karl Foerster’)
Northern sea oats (Chasmanthium latifolium) grows to 2 – 3ft in sun to partial shade. Switchgrass (Panicum virgatum ‘Heavy Metal’, ‘Dallas Blues’ and other cultivars)