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Growing Ornamental Grasses

Grasses are not a summer fancy. They add interest to all seasons.

Grasses are not a summer fancy. They add interest to all seasons.

Ornamental grasses can be used as fillers or specimens, border plants or background plantings, as ground covers or screens, or they may be grown as container plants. Their adaptability and subtle beauty make them perfect companions to flowering plants and other woody ornamentals.

Grasses can be used in the landscape just like perennials, but their usefulness extends far beyond that of a normal perennial. Grasses are useful for erosion control, space barriers, wildlife shelters, winter interest, as a background to flowering plants, and as architectural features, to name a few.

Grasses add the dimensions of sound and movement to the garden as wind catches and rustles the leaves. The dried stalks of many grasses remain upright for winter interest. The wide variety of colours, sizes and growth habits of grasses assures that one will fit almost any garden.

The term ornamental grass is used to include not only true grasses (Gramineae) but close relatives such as sedges (Cyperaceae) (Carex), rushes (Juncaceae), Liriope, hardy bamboos (particularly the genus Phyllostachys), and others. The flower spikes (also known as inflorescences) can be found in different shades of maroon, red, pink, silver, white, yellow, or beige and are excellent for drying.

Ornamental grasses are not the kind of grasses that you broadcast spread across the front or back yard. Hopefully, you will never run across them with the lawn mower, either. Rather, Ornamental grasses are decorative. They look great in the flower garden. They are used to add depth and texture to highlight rock gardens. They are mixed amidst shrubs.

Ornamental grasses add grace and motion to the garden with strap-like foliage that sways in the gentlest breeze. The fluffy flowers and seed heads on many varieties last throughout the winter, attracting birds and adding winter interest to the garden.

Ornamental grasses include many species with different textures, sizes, colours, and flower forms. Each grass species has it’s own unique form. They may form low compact mounds, tall screens, or densely spreading mats. The foliage colours include various shades of green, blue and red, as well as variegated varieties having red, white or yellow foliage banded with ivory or yellow stripes. In the fall, the spring and summer colours change to hues of red, beige, or brown, providing a great winter garden accent.

Scores of ornamental grasses are now in use with many new forms continuously being added. Speculation as to the reasons for this astonishing rise in popularity appears to centre round the practical, as well as aesthetic merit of ornamental grasses as a whole. Many of the ornamental grasses have an inherent ability to handle both the drought years as well as the wet years, are eagerly sought.

Ornamental grasses fit into the herbaceous (non-woody) category of earth’s vegetation and they are divided into two categories: cool-season and warm season. As the name suggests, cool season grasses make their best growth during the spring and autumn and usually become dormant or semi-dormant during the heat of summer. Feather Reed Grass and Blue Fescue are prime examples.

Warm season grasses make their best growth during long summer days and go dormant during the winter. The popular Maiden Grasses are examples of warm season grasses.

SELECTING GRASSES

The selection of available grass cultivars is ever increasing. One will find a wide range of height, spread, colour, and flowering times available. Some grasses have become invasive in some areas, have been declared noxious weeds and have been banned from being grown in home gardens. Again seek the advice of a local extension office or garden centre before planting grasses.

One of the two key things to consider when selecting a grass is it’s height.

Tall (2m or more), upright growing types create visual interest, especially when used towards the back of a border. Their bold lines break up space over a long season, some remaining attractive well into the winter. These are the big guys! Plan their placement carefully because you won’t be able to move them easily!

Medium-sized (60cm to 2m) grasses may be effectively massed together, particularly in gardens with a low maintenance emphasis. Spring-flowering bulbs combine well with these for early season interest. These grasses also can be used a specimen plants throughout your garden without taking up too much space.

Low-growing (less than 60cm) grasses are ideal for edging around shrubs or combining with spreading evergreens. When mass-planted, they will form an attractive low-maintenance groundcover.

The second key thing to consider when selecting a grass is climate. Check carefully with your local nursery, garden centre or extension office as to which varieties will do well in your area. Some varieties which you may favour will drop off of your list. But don’t be down! There are many attractive grasses available for even some of the harshest climates!

BAMBOOS

Bamboos are also grasses; they are made stiff by the presence of silica in their stems.  Often overlooked by homeowners, bamboos are a nice evergreen addition to the ornamental grass palette. The Giant Bamboo Forest in Asia is the endangered habitat of the Giant Pandas; however, there are a wide variety of smaller bamboos that are useful in a garden setting.

Many bamboo plants are tender, but there are bamboos that are hardy in colder climates.  Some bamboos will die back to the ground in the winter, but will sprout anew in spring.  There are two types of bamboo:  running bamboo and clumping bamboo.  Running bamboos can be quite invasive; therefore it is important to plant them in an area in which they can be contained or where their running habit is an asset, not a detriment.  Clumping bamboos do not spread; they form clumps. Several bamboos have interesting shaped canes, or stems—there are golden bamboos and bamboos with zigzag canes.  Bamboos are usually evergreen and therefore provide good winter interest.

SITE SELECTION

Most ornamental grasses reside in full sun, having spent most of their existence in savannas, tundras and coastal plains. Understanding their origins help explain the types of soil they prefer, opting for sandy soils over loams and clay.

They don’t need copious amounts of rainfall or watering to exist and can easily survive extended periods of drought. This is why they do so well in xeriscape gardens and those created to be drought-tolerant.

It’s best not to grow grasses with high water-dependent plants as either the grass will struggle with excessive moisture or the water needy will suffer from not enough. Group ornamental grasses with succulents, cacti and grey-foliage plants for their best rate of survival.

PROPAGATING GRASSES

This is by far one of the easiest plant families to propagate after succulents. The most effective method is via collecting seed and distributing in situ. Some, like the Japanese Blood Grass, can be divided and propagated this way which can be just as successful but takes more effort.

The problem with grasses is not their ability to propagate but that they are so successful at it. You may find yourself weeding more often if you don’t want them to spread beyond their boundaries. In order to prevent reseeding, harvest the flower heads before they’re fully dry.

PLANTING INSTRUCTIONS

Ornamental grasses are most commonly purchased pre-planted in 5 litre containers. Plant in spring, spacing plants 30cm to 1m apart, depending on the variety. Prepare the garden bed by using a garden fork or tiller to loosen the soil to a depth of 30cm to 40cm, then mix in a 5cm to 10cm layer of compost. Dig a hole twice the diameter of the pot the plant is in. Carefully remove the plant from its container and place it in the hole so the top of the root ball is level with the soil surface. Carefully fill in around the root ball and firm the soil gently. Water thoroughly.

CARE

Apply a thin layer of compost each spring, followed by a 5cm layer of mulch to retain moisture and control weeds. Water plants during the summer if rainfall is less than 25mm per week. Cut back the plant in late winter to stimulate new growth. Some species need dividing every 3 to 4 years to keep the plants vigorous. Taller species, such as fountain grass, may need staking.

ORNAMENTAL GRASSES IN CONTAINERS

Growing ornamental grasses in containers is a great way to feature grasses without the worry of them spreading or taking over the garden.

COMPANION PLANTS FOR ORNAMENTAL GRASSES

When talking about selecting grasses we spoke about tall, medium sized and low-growing grasses. We have therefore selected companion plants using similar grouping.

Companion Plants for Tall Grasses

· Aster — Summer and Autumn bloomers in shades of pink, purple and blue.

· Bronze Fennel — Feathery, bronze foliage.

· Cleome — Airy pink, purple or white flowers from mid summer to autumn. Annual.

· Cosmos — A self-sowing annual in a variety of colours.

· Digitalis ferruginea (Rusty Foxglove) — Excellent for adding height.

· Echinacea (Purple Coneflower) — A classic companion plant.

· Eryngium (Sea Holly) — Wonderful for adding texture.

· Gaura (Appleblossom Grass) — Not really a grass, but it’s a great perennial.

· Knautia — A good filler with a long bloom season.

· Liatris — Provides a vertical accent.

· Lychnis — Brightly coloured flowers are a real standout.

· Monarda (Bee Balm) — Attracts butterflies and hummingbirds.

· Perovskia (Russian Sage) — Bushy perennial with lavender-blue flowers.

· Rudbeckia — Large, daisy-like flowers. Blooms in late summer and autumn.

· Verbena — Self-sowing, first-year flowering perennials.

· Solidago (Goldenrod) — Yellow flowers in late summer.

Companion Plants for Medium-Size Grasses

· Alyssum — Masses of tiny white flowers.

· Asclepias (Butterfly Weed) — Bright orange flowers. Drought-tolerant.

· Campanula rotundifolia — Beautiful, blue colour all summer long.

· Coreopsis — Golden yellow or brick red flowers.

· Daylilies (Hemerocallis) — Many colors to choose from.

· Eschscholzia (California Poppy) — Long-blooming annual.

· Hyssop — Stunning blue color. Repeat blooms.

· Lavatera — A nice annual for filling in the gaps.

· Lobelia — Perennial species do well with shade-tolerant grasses.

· Oenothera (Evening Primrose) — Bright yellow flowers.

· Penstemon — Blooms in early summer. Foliage and seed pods are nice in autumn.

· Platycodon (Balloon Flower) — White, blue or pink flowers.

· Salvia superba — Violet-blue or pink flowers. Reliable perennial.

· Scabiosa ochroleuca — A nice filler with pincushion-style flowers.

· Zinnia — Summer blooming annuals.

Companion Plants for Short Grasses

· Campanula carpatica Compact, blue bellflower.

· Cosmidium ‘Phillipine’ Unusual colour. Long-blooming annual.

· Dianthus deltoides Very short, spreading perennial with vibrant flowers.

· Iberis gibraltarica Lavender-pink flowers in spring. Repeat blooms.

· Lavender ‘Lady’ Compact and long-blooming. Fragrant.

· Salvia ‘Lady in Red’ — Red flowers for hummingbirds. Annual.

· Salvia ‘Purple Volcano’ — Burgundy-purple foliage makes a nice contrast.

· Viola (Pansy) — Self-sowing, short-lived perennials.