Ornamental Perennial Grasses
Ornamental grasses add an element of movement and shape to the garden. Animating the most basic of garden borders without sacrificing structure. Attractive, yet highly adaptable, grasses are tolerant of most garden soils and even grow in partial shade. This low-maintenance group of perennials has been growing in popularity and for good reason.
Short Grasses Height Less Than 46cm (18”)
Quaking grass (Briza media): Forms a low tuft of green leaves with delicate loose clusters of heart shaped flowers that appear in late May. Looks superb when combined with heaths and heathers. Plant it in full-sun, with a lean well-drained soil. Grows to a height of 25-45cm (10-18”) and a spread of 30cm (12”).
Variegated Japanese sedge (Carex morrowii): A great grass for brightening up a damp shady area. The cascading tufts of creamy white and green foliage work well with sedums and euphorbia. A perfect choice for growing in containers. Plant in full-sun or shade, with a rich, moist soil. Grows to a height of 30cm (12”) and spread of 15-30cm (6-12”).
Blue fescue (Festuca ovina ‘Glauca’): Low tufts of steely-blue foliage produce tan coloured spikes in late spring. They look great in containers and colour-up best in full sun. Popular as an edging, or massed to create a low, hummocky groundcover. It will grow happily in both full-sun or part-shade, and only needs an average well-drained soil. Grows to a height of 23-30cm (9-12”) and a spread of 15-23cm (6-9”).
Japanese blood grass (Imperata cylindrica ‘Red Baron’): a striking, upright grass that spreads slowly to form a medium-sized clump, so is an excellent choice for planting en masse. The dramatic foliage is green at the base and blood-red on top making it a superb colour compliment for blue conifers and yellow-flowering perennials. Be sure to protect this one from the winter cold and excessive wet. Plant it in either full-sun or part-shade, with a moist, well-drained soil. Grows to a height of 45cm (18”) and spread of 30cm (12”).
Variegated moor grass (Molinia caerulea ’Variegata’): A compact grass with beautiful creamy-yellow variegation and persistent, showy purple flowers. This is a desirable small ornamental grass for the lightly shaded perennial border. Plant it in full-sun, with moist, fertile, slightly acidic soil. Grows to a height of 30-45cm (12-18”) and spread to 30-45cm (12-18”). The flowers reach 15-30cm (6-12”) above foliage.
Medium-Sized Grasses Height Between 46-92cm (18-36”)
Leatherleaf sedge (Carex buchananii): Delicate strands of bronze foliage form a tufted arching fountain which is a superb contrast when placed next to dwarf conifers or other evergreens. The arching blades also look splendid beside water. Plant it in full-sun or shade, with a rich, moist soil. Grows to a height of 45cm (18”) and a spread of 30cm (12”).
Northern sea oats (Chasmanthium latifolium): This clumping grass is absolutely magnificent, treasured for its showy, dangling flower spikes and rich bamboo-like foliage. Both foliage and flowers mature from a saturated lime green colour in spring to a soft copper in fall. Performs well in full sun but is particularly valued for its shade tolerance. Plant it in full-sun or shade, with a rich, moist soil. Grows to a height of 76-90cm (30-36”) and a spread of 30cm (12”).
Fountain grass (Pennisetum alopecuroides): The buff-coloured flowerheads on this grass resemble large foxtails, and appear as early as July. Medium-sized clumps of cascading green foliage turns bright almond colour in the fall. Blooms best in a warm location. Plant it in full sun, with an average, well-drained soil. Grows to a height of 30-90cm (12-30”) and a spread of 60-90cm (24-30”).
Giant feather grass (Stipa gigantea): One of the showiest and most spectacular of all flowering grasses. The narrow, arching, rolled leaves form dense tufts and in May flower stalks gracefully arch up from the grey-green foliage. It is stunning when the airy sheaves of yellowish flowers shimmer and dance in the breeze. Plant it in full sun, with a fertile well-drained soil. Grows to a height of 60cm (24”) and spreads 60cm (24”), but the flowers reach another 8-10cm (3-4’) above the foliage.
Mexican feather grass (Nassella tenuissima): This compact species forms a low clump of fine hair-like bright green foliage. In mid-summer spikes of bearded silky-green flowers appear slowly changing into attractive golden-blonde plumes. Dances in the slightest breeze from June all the way into late fall. Plant in full sun, with fertile well-drained soil. Grows to a height and spread of 30-60cm (1-2’).
Tall Grasses Height Greater Than 92cm (36”)
Tall cultivated ornamental grasses are almost exclusively varieties of the genus miscanthus. Below are described a few of the commonly available varieties and their unique traits. However, all share similar fluffy flowerheads that appear in the fall and hold their shape well into winter. These flowers appear to float with the wind and are most suitable at the back of the border (with the exception of a few dwarf varieties). Pair them with evergreens to really make them standout.
Giant silver grass (Miscanthus sacchariflorus ‘Robusta’): This very tall grass has a bamboo-like tropical appearance, quickly forming a patch of tall, stout corn-like stems and graceful arching foliage. In autumn the silvery plumes mature to a red, as the foliage turns to an attractive reddish-orange. This plant grows easily and fast so be sure to plant it accordingly. Plant it in full sun or part shade, with a rich, moist soil. Grows to a height of 1.8 m (6’) and spread of 90cm (3’).
Japanese silver grass (Miscanthus sinensis): This is one of the most graceful and self-defining of all the ornamental grasses. The grasses listed below are in fact varieties of this species. Plant in full sun or part shade, with a moist but well-drained soil. Can grow from 0.8-2m in height (3-7’) but on rare occasions can get as tall as 4m (13’), with a spread of 90cm (3’).
Chinese silver grass (M. sinensis ‘Gracillimus’): Has fine-textured, long, narrow green foliage and a graceful arching form. The copper-red flower heads open in late September. Grows to a height of 1.2-1.8m (4-6’).
Flame grass (M. sinensis ‘Purpurascens’): Of all miscanthus this one has the most reliable red-orange autumn foliage. Rosy-coloured flower spikes appear as early as July. It will grow in shade but instead of the burning red foliage you will see a variety of pastel hues, not quite living up to its common name. Grows to a height of 1.2-1.5m (4-5’).
Silver feather grass (M. sinensis ‘Silberfeder’): An older European selection and still one of the best grass cultivars available today. Rich green foliage with a graceful, arching, vase shape. In August this grass becomes adorned with shimmering, silvery-white plumes. Grows to a height of 1.5-1.8m (5-6’), mature plants may require staking.
Porcupine grass (M. sinensis ‘Strictus’): A unique award-winning specimen plant with spiky, stiff, bright green foliage that features horizontal, yellow banding similar to M. sinesis ‘Zebrinus’ but tighter, more upright and much hardier. Copper blooms appear in September rising 30-60cm (1-2’) above the foliage. Grows to a height of 1.5-1.8m (5-6’).
Variegated silver grass (M. sinensis ‘Variegatus’): A very bright and showy arching clump with distinct green and white striped leaves. Creamy-pink flower plumes appear in September as the foliage matures to an almond hue. Grows to a height of 1.5-1.8m (5-6’), and mature plants may require staking.
Grasses actually prefer to be grown on the lean side. They will be sturdier without the addition of the high-powered nutrients. The best plan is to use a slow-release fertilizer such as GARDENWORKS All Purpose. You may be tempted to use a lawn fertilizer since it’s grass, but resist. Have you noticed how quickly the lawn grows after fertilizing? Tall-growing ornamental grasses will bolt for the sky and with such rapid growth will be unable to hold themselves up. This will result in weak, floppy plants. The only exception to the rule is miscanthus, it does better with some extra fertilizer and moisture. The solution to the potential flopping problem is to use organic fertilizers such as well-rotted manure, sea-soil or compost.
Ornamental grasses need to be well watered their first year in order to get good root establishment. During this first year the plant will need about 3-5cm of water per week to establish the root system. Once the root systems are established, the plants are better adapted to lower moisture levels. Mulch is a good idea for the first year, but do not mulch right to the crown of the plant. This can cause the crown to rot because of the constant moisture.
How Deep to Plant
It is very important to plant your ornamental grasses so that the crown of the plant is level with the soil’s surface. Some grasses, in particular pennisetum, are very sensitive to being planted too deep. The crown rots and the plants die.