Eagle Lake Nurseries Gardening Tips July 2007 Perennial Ornamental Grasses The prairie climate of southern Alberta is well suited to growing ornamental grasses. Striking foliage and unique seed heads make these plants stand out in the garden, providing three seasons of interest since they last into the winter months. They are rarely attacked by pests, are not prone to disease problems and require little maintenance beyond cutting back in late winter or early spring. There is great variation in height among grasses, from the diminutive fescues at 25cm to Ravenna grass topping out at 2m. Most grasses prefer dry soil and full sun, but for a damp site plant one of the moisture tolerant varieties: bulbous oat grass, moor grass or ribbon grass. Ravenna, ribbon and blue lyme grass are all invasive species! These should be planted in a large pot, 5 gallon or bigger, and the pot sunk in the ground leaving a 2cm lip above soil level unless you have the space to let the spreading rhizomes run. The attractive, low growing tufts of blue fescue make it popular in rock gardens, at the front of borders and in natural landscapes. It should be divided and split every three years approximately, or when the center begins to die out. ‘Elijah Blue’ fescue [Festuca ovina glauca ‘Elijah Blue’] displays a striking, intense foliage colour, as does blue oat grass [Helictotrichon sempervirens]. This grass forms clumps of thin arching silver-blue leaves with beige clusters of flowers and grows 75cm tall. Blue lyme grass [Leymus arenarius] is taller at 1m, with wider, grey-blue strap shaped foliage. Narrow spikes of beige flowers last well into the winter. The switch grasses [Pannicum virgatum] also add height to the garden display, growing to 1m tall. ‘Heavy Metal’ has metallic blue foliage, ‘Prairie Sky’ is blue-green and ‘Shenandoah’ is unusual, with blue-green leaves tinged with dark red. Delicate, airy flower spikes rise above the sturdy clumps of this hardy, decorative grass. Another tall variety is feather reed grass [Calamagrostis x acutiflora] which grows to 1.25m with upright elegant pinky-beige flowers that last many months and are popular for dried flower arrangements. ‘Karl Foerster’ has narrow green leaves, while the slightly smaller reed grass, ‘Overdam’ displays attractive variegated green and white foliage. Molinia caerulea ‘Variegata’ is a lower growing grass, at 60cm tall. It prefers a damper site than many grasses, and has dense tufts of yellow and green leaves, with delicate stalks of purplish flowers. Also with variegated foliage and preferring moist soil, bulbous oat grass [Arrhenatherum bulbous ‘Variegatum’] grows to half a meter tall, having narrow green and white leaves. Robust ribbon grass has spreading rhizomes which enable it to stabilize slopes, and wider green and white foliage. This grass lasts well into the winter. For an unusual variegated grass with creamy-yellow and green vertically striped foliage, try ‘Skinner’s Gold’ brome grass [Bromus inermis ‘Skinner’s Gold’]. Its bronze-purple flower spikes look good in flower arrangements. For a tall green grass with striking flower plumes it is hard to find a better subject than Ravenna grass [Erianthus ravennae] which will grow to 1.5m. The stately inflorescences resemble those of pampas grass, which is not hardy in our zone. Smaller, at 90cm, fountain grass [Pennisetum alopecuroides] also displays creamy white flower plumes above arching green leaves and is less invasive than Ravenna grass. A native prairie grass of about the same size is little blue stem [Schizachyrium scoparium] with delicate translucent seed heads and folding green leaves. This specimen is good for dry gardens. Although not a grass, a plant that may be used for similar foliage effect in a dry area is ivory tower yucca [Yucca filamentosa ‘Ivory Tower’]. Yucca is a desert plant with rigid, spiky, grey-blue foliage which may take several years to mature, when it is adorned by spectacular spikes of creamy bell-shaped flowers. Do not cut back the leaves in winter, it grows like a semi-evergreen and will not tolerate trimming. These grasses will complement the flowers and shrubs in your garden providing long lasting interest. They may also be useful in planters and pots, adding height and focus to displays, but should be transplanted to the garden before freezing if you wish to preserve them for next season. Caroline Fine Eagle Lake Nurseries Ltd.