Ornamental grasses are categorized as either cool-season or warm-season, with either running or clumping growth habits.
Cool-season: Grows best at temperatures from 15 to 24°C. New growth begins as soon as temperatures rise above freezing in spring. Growth slows and flowers bloom by early summer.
Warm-season: Grows best at temperatures from 26 to 35°C. New growth begins after soil warms up to 16°C. Growth slows and flowers begin by midsummer, continuing through fall.
Running growth habit: Ranging from slow creepers to aggressive spreaders, running grasses are useful for erosion control on slopes or as ground cover.
Clumping growth habit: These grasses grow in tufts. They make fine specimens and are also effective planted in groups or masses. Most ornamental grasses used in the garden are clump-forming.
Bouteloua gracilis (blue grama)
Description: Fine-textured, light-green foliage grows to 20 centimetres. Comb-like inflorescences emerge silvery white in June and turn purplish as they mature through September. Uses: Stunning in groups or masses, as a specimen, in rock gardens or as a lawn substitute. Heat tolerance makes this an excellent grass for the Interior. Preferences: Full sun. Loamy or sandy soil. Will tolerate moderately acid or dry soils, as well as extreme cold and heat. To Zone 3.
Calamagrostis x acutiflora ‘Karl Foerster’ (Feather Reed Grass)
Description: Rich green, shiny foliage up to two metres tall and half a metre wide, gives rise to upright, feathery panicles in June that can reach 2.5 metres. Uses: Wonderfully versatile in the landscape. As a specimen, a backdrop or in masses, this grass adds tremendous vertical accent and movement to the garden. Preferences: Full sun. Well-drained, fertile soil. Will tolerate a wide range of soil types, including dry soils and heavy clay. To Zone 4.
Carex muskingumensis (Palm Sedge)
Description: Exotic foliage resembles palm fronds. Fine leaves radiate from arching culms up to a metre in length. Inconspicuous brown flowers June through September. Uses: An excellent ground cover or mass planting for moist areas. Affords erosion control for moist banks. Showy in containers and water gardens. Preferences: Shade or sun. Moist to wet soil. Needs constant moisture in hot, dry conditions. Will grow in water up to 10 centimetres deep. To Zone 2.
Chasmanthium latifolium (Northern Sea Oats)
Description: Light-green, bamboo-like foliage on stems reaching one metre high. Decorative, drooping inflorescences start out green in June and mature to copper through September. Uses: A lovely flowering accent for shady and damp spots. Effective en masse in containers. This salt-tolerant grass is an excellent choice for coastal gardens. Preferences: Full sun or shade (shade in hot climates). Deep, rich soil. Will tolerate a variety of soil conditions with ample moisture. To Zone 3.
Helictotrichon sempervirens (Blue Oat Grass)
Description: Handsome, bright blue foliage. Dense, sharply pointed leaves reach 60 centimetres tall and wide. Attractive flowers June through August emerge bluish-white and dry to a golden-straw colour. Uses: A lovely accent in borders and rock gardens, planted alone or in masses. Give it ample space in mass plantings. Preferences: Full sun or light shade. Well-drained, fertile soil. Will tolerate a range of soils with good drainage. To Zone 4.
Miscanthus sinensis (Chinese Silver Grass) and Cultivars
Description: These are considered among the most ornamental of all the grasses. Varieties range in height from one to three metres, offering a wide spectrum of size and colour in both foliage and flowers. Noteworthy cultivars include: ‘Gracillimus,’ ‘Purpurascens,’ ‘Sarabande,’ ‘Strictus’ and ‘Variegatus.’ Uses: Ideal for large-scale landscaping. Highly effective as a tall background, screen or hedge, by water’s edge or in water gardens. Preferences: Full sun. Moist, fertile soil. Requires ample moisture in hot, dry conditions. To Zone 5.
Pennisetum alopecuroides (Fountain Grass)
Description: Glossy, bright-green foliage reaches 90 centimetres tall and wide. Showy, bottlebrush inflorescences on slightly arching stems emerge cream to tan in August and mature to reddish-brown through September. Seed-heads add interest well into winter. ‘Hameln’ is a popular cultivar. Uses: Effective in mass plantings or as a specimen. This fine candidate for the mid- to back of the border provides interest long after many garden blooms have quit. Preferences: Full sun or light shade. Moist, well-drained soil. Will tolerate a wide range of soils with good drainage. Protect from severe cold in winter. To Zone 5.
Stipa gigantea (Giant Feather Grass)
Description: This spectacular flowering grass features open, oat-like flower spikes up to 2.2 metres tall, held high over dense, evergreen clumps of arching, grey-green foliage. Flowers in May, with showy, spent flower stalks persisting into fall. Uses: An indispensable specimen or tall flowering accent whose height can be used to striking effect in the perennial border. Preferences: Full sun. Fertile, well-drained soil. Interior gardeners should grow this grass in a sunny, protected site or provide winter protection. To Zone 6.