Ornamental grasses, with their natural grace and diversity, blend harmoniously into almost any garden design. They bring height, texture, movement, and a palette of colours that changes with the seasons. Their growing popularity is a testament to their appeal and sparks curiosity. This guide provides you with the essential basics for successfully growing them, from planting to maintenance.
Choosing the Right Grasses
Before planting, take a moment to choose species that will thrive in your environment. Consider the sunlight in the planting area (full sun, part-shade, shade), soil type, and moisture levels. Also, think about the desired effect: some grasses are compact and ideal for borders, while others, majestic, create striking focal points or privacy screens. Carefully read plant labels to learn about their specific needs and mature size.
When to Plant Grasses?
For optimal recovery and establishment, two periods are particularly favourable for planting:
- In the spring: After the last risk of frost, when the soil begins to warm up. This allows plants to develop a strong root system before the summer heat and potential dry spells arrive.
- In the fall: Ideally 6 to 8 weeks before the first killing frost. Cooler temperatures and autumn rains promote rooting before winter.
Grasses bought in containers can often be planted throughout the growing season, provided you ensure consistent watering after planting, especially in hot, dry weather.
How to Plant Grasses?
For optimal visual impact, plant grasses in clumps or groups of three or five plants (odd numbers), respecting their final mature spacing.
- Dig a planting hole two to three times wider than the root ball and just as deep. Loosen the soil at the bottom of the hole.
- If your soil is poor or very compact, mix well-decomposed compost into the backfill soil. Most grasses do not like overly rich soils.
- Gently remove the plant from its pot. If the roots are circling (root-bound), gently tease them apart with your fingers or make a few vertical cuts with a clean knife.
- Place the root ball in the hole so that the top of the root ball (the crown) is level with or very slightly above the surrounding soil level.
- Fill the hole with the prepared soil, tamping lightly around the root ball to eliminate air pockets.
- Water thoroughly after planting to soak the soil well and encourage contact between the roots and the earth.
Important Points for Planting:
- Drainage: Most ornamental grasses require excellent drainage. They dislike constantly soggy soils, especially in winter. If your soil is heavy clay, consider planting on a mound or significantly improving drainage.
- Soil Type: Although they are generally not very demanding, some grasses have preferences. Always check the specific needs of the chosen variety.
- Drought Tolerance: Once well-established (which can take a full season or even two), many grasses are remarkably drought-tolerant.
- Specific Water Needs: Pay attention to the label. So-called "prairie" grasses (e.g., Panicum, Schizachyrium) are very drought-tolerant once established and require little water. Grasses of "woodland" origin or from wet environments (e.g., some varieties of Carex or Hakonechloa) will prefer soil that stays cooler and moist.
Simplified Maintenance
One of the great advantages of ornamental grasses is their low maintenance needs. By planting them in the right spot from the start (adequate light and soil conditions), you will minimize future care.
Here are some tips for their long-term care:
Cutting Back Plants (Annual Pruning):
For tall grasses, tie the tops of the stems together with string before cutting. This will make collecting the clippings much easier.
- Cool-Season Grasses (e.g., Festuca, Calamagrostis, some Carex): These grasses start growing early in the spring. Cut them back in early spring (March-April), before new growth is too developed, to enjoy their winter presence for as long as possible. Cut the dried foliage to about 10-15 cm (4-6 inches) from the ground.
- Warm-Season Grasses (e.g., Miscanthus, Panicum, Schizachyrium): These grasses start growing later. They can be cut back in the fall after they have browned and dried, or preferably, in early spring (April) before new shoots appear. Leaving grasses in place during the winter offers striking visual interest with frost and snow, as well as providing shelter and food for wildlife. Also cut them to about 10-15 cm (4-6 inches) from the ground.
Dividing Clumps:
Over time, the centre of some grass clumps can become bare and lose vigour. Division helps rejuvenate plants, control their size, or simply multiply your specimens for other parts of the garden or to share.
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When to Divide?
- Warm-season grasses: Divide them in the spring, when new growth begins, until early summer.
- Cool-season grasses: Divide them in the spring or early fall, when temperatures are milder.
- How to Divide? Use a sturdy spade, a strong utility knife, or even a hatchet for very large, well-established clumps. Dig up the entire clump if possible, or extract sections from the periphery. Separate the clump into several divisions, each with healthy roots and shoots (like slices of a pie).
- Replanting: Replant the divisions promptly to prevent the roots from drying out. Water well after replanting.
- Precautions: Always wear gloves and long sleeves, as the edges of many grass blades can be sharp.
Fertilizing:
Most ornamental grasses come from natural environments where soils are not particularly rich (prairies, woodland edges). They feed on the decomposition of their own foliage and that of surrounding plants.
- Organic Mulch: A mulch of shredded leaves or compost applied in the fall around the base of the plants is usually sufficient for their nutritional needs.
- Avoid Excess: No additional fertilization is usually necessary. In fact, an excess of fertilizer, especially nitrogen, can be harmful to many grasses, causing floppy growth, a tendency to splay open, and reduced flowering.
Pests and Diseases
Ornamental grasses are generally not very susceptible to diseases or pest attacks, which reinforces their easy-care nature. Good air circulation and adequate drainage prevent most problems.
Winter Appeal
Don't underestimate the beauty of grasses in winter! Their dried stems and flower heads often persist, catching the low light, frost, and snow, adding structure and interest to the dormant garden. The rustling of their foliage in the winter wind is also a subtle charm.
Some Popular Grasses to Beautify Your Garden
Here is a selection of grasses valued for their beauty and resilience, suited to a wide range of conditions:
- Calamagrostis x acutiflora 'Karl Foerster' (Feather Reed Grass): Upright and narrow habit, decorative plumes from early summer, long-lasting. Sun. (Height: 1.2-1.8m / 4-6 ft)
- Panicum virgatum and its cultivars (Switchgrass): Vertical structure, fine foliage turning superb fall colours (red, purple, orange depending on the cultivar). Airy flower heads. Sun. (Height: 0.9-1.8m / 3-6 ft)
- Schizachyrium scoparium (Little Bluestem): Fine foliage with bluish hues in summer, turning orange, copper, and red in the fall. Upright habit. Sun. (Height: 0.6-1.2m / 2-4 ft)
- Festuca glauca (Blue Fescue): Small grass forming a compact cushion, intense silvery-blue foliage. Ideal for borders or rock gardens. Sun, well-drained soil. (Height: 20-30cm / 8-12 inches)
- Molinia caerulea and its cultivars (Moor Grass): Arching clumps of fine foliage, delicate and airy flower heads. Beautiful fall colours. Sun to part-shade. (Height: 0.6-2m / 2-6.5 ft depending on cultivar)
- Sporobolus heterolepis (Prairie Dropseed): Very fine foliage forming a dense, rounded clump, emitting a subtle scent of coriander or popcorn in late summer. Delicate and airy flower heads. Superb amber colours in the fall. Sun. (Height: 0.6-0.9m / 2-3 ft)
By incorporating these tips into your gardening practices, you'll discover that ornamental grasses are valuable allies in creating a dynamic, attractive, and easy-to-live-with garden all year round.
