How to Divide and Replant Ornamental Grasses

Ornamental grasses bring movement, texture and year-round structure to Australian gardens. Their fine leaves soften paving, screen outdoor areas and add interest when many flowering plants have finished. Over time, however, a grass can become crowded, develop a bare centre or spread beyond the space allowed for it.

Dividing an established clump is a practical way to rejuvenate the plant and create several new specimens at little cost. With the right timing, sharp tools and suitable aftercare, you can lift, split and replant grasses successfully in gardens ranging from cool Melbourne courtyards to warm Brisbane backyards.

Task	Best approach	Main reason
Choose the timing	Divide in late winter or early spring in cool areas; early autumn can suit mild districts	Roots establish before weather becomes extreme
Prepare the site	Clear weeds and improve compacted soil with compost	New divisions need air, moisture and nutrients
Cut the clump	Use a spade, pruning saw or garden knife according to size	Clean cuts reduce tearing and root damage
Replant divisions	Place them at the original soil depth	Deep planting can cause crown rot
Water after planting	Soak thoroughly, then keep soil evenly moist	Encourages fresh root growth without waterlogging

Choose the right time and plant

The most suitable time depends on the grass, your climate and the plant’s growth cycle. Most warm-season grasses, including pennisetum, lomandra and miscanthus, are best divided as new shoots begin appearing in late winter or spring. In southern Australia, this may be September or October, while gardeners in warmer parts of Queensland or New South Wales may work slightly earlier.

Cool-season grasses can sometimes be divided in early autumn, provided the soil is still warm and the plants have enough time to establish before winter. Avoid dividing during heatwaves, severe drought, waterlogged conditions or periods of heavy frost. A newly split root ball loses some of its ability to take up water, so mild weather makes recovery much easier.

Look for a mature clump that has become too large for its position, produced fewer flowers or developed a dead, thin centre. Plants with vigorous green growth around the outside and a dense root system usually provide the best divisions. Very young plants may not have enough material to separate, while severely diseased clumps should be removed rather than propagated.

Prepare tools, soil and planting spaces

Water the parent plant deeply one or two days before lifting it. Moist soil holds around the roots and makes digging less stressful, although saturated soil can turn heavy and difficult to handle. Cut back tall foliage before working, leaving roughly 15 to 30 centimetres of leaves. This reduces the plant’s water loss and gives you a clear view of the crown.

Wear sturdy gloves because grass blades can cause surprisingly sharp cuts. Helpful equipment includes a sharp spade, hori hori knife, pruning saw, secateurs, tarp, bucket of water and a clean pair of loppers for tough roots. Disinfect cutting tools before and after use, particularly when dividing plants showing spots, rot or unusual dieback.

Prepare the new positions before splitting the plant so the roots are exposed for the shortest possible time. Remove competing weeds and loosen the soil to the depth of the root ball. Mix a modest amount of compost into poor soil, but avoid creating a rich pocket in otherwise lean ground. Many ornamental grasses prefer free-draining soil and can produce weak, floppy growth when overfed.

In Australia, check the plant’s mature width before choosing a position. A clump that looks small at a nursery can become substantial after two or three growing seasons. Local nurseries and garden centres often stock smaller divisions that suit narrow suburban blocks, while larger specialist growers may offer unusual forms for acreage gardens.

Lift the parent clump carefully

Start by tying the foliage together with soft twine. Drive the spade vertically into the soil around the outer edge of the clump, leaving enough distance to avoid slicing through the main crown. Work around the plant, pushing the blade down as deeply as possible. For a large specimen, it may be easier to dig a trench around it before levering the root mass upwards.

Use the spade as a lever only after most of the surrounding roots have been loosened. Pulling hard on the leaves can break the crown and separate foliage from the roots. Once lifted, place the clump on a tarp and brush or hose away some soil if the root structure is difficult to see. Do not leave the exposed roots in direct sun or drying wind.

Small clumps may separate naturally when you tease them apart by hand. Larger root balls often need a sharp spade or pruning saw. Aim for sections that each contain healthy roots and several strong shoots. A division with one tiny shoot and little root material may survive, but it will take much longer to fill out.

Split the grass into healthy divisions

Position the blade through the crown and make one decisive cut rather than repeatedly hacking at the same spot. Each piece should be substantial enough to support itself. For many medium-sized grasses, divisions around 10 to 20 centimetres wide work well, though the ideal size varies considerably between species.

Remove dead material, hollow roots and any soft, dark sections as you work. If the centre of the clump is completely woody or dead, discard it and use the vigorous outer portions. Keep the roots damp in a bucket or wrap them in a wet towel while you finish dividing. Avoid storing divisions in standing water for hours, as low oxygen can damage fine roots.

Some plants commonly called grasses, such as mondo grass, liriope and dianella, divide differently from large tussock-forming species. Their crowns may pull apart into smaller rosettes, while bamboo-like or strongly rhizomatous plants may require a saw. Always check the growth habit before cutting, and be cautious with running species that can spread into neighbouring beds.

Clean division also helps control size. Rather than making many tiny pieces, create a few robust plants that will establish quickly. This is particularly useful in areas with hot summers, such as Adelaide, Perth and inland New South Wales, where small root systems can dry rapidly before they have anchored into surrounding soil.

Replant at the correct depth

Set each division into its prepared hole so the crown sits level with the surrounding soil. The crown is the point where shoots meet roots, and burying it too deeply can trap moisture and encourage rot. Backfill gently, firm the soil around the roots and check that no large air pockets remain.

Space the divisions according to their eventual size, not their appearance on planting day. A compact clump may need 40 centimetres of room, while a tall miscanthus or large pennisetum can require more than a metre. Planting too closely creates competition for water and air circulation, leading to thin growth and more maintenance later.

A layer of organic mulch helps reduce evaporation, especially in exposed Australian gardens, but keep it a few centimetres away from the crown. Sugarcane mulch, composted bark and other suitable products can work well when applied moderately. In areas with wet winters, use a lighter mulch layer so the crown remains dry and breathable.

For a polished landscape, repeat divisions in groups rather than scattering single plants randomly. Low grasses can edge a path, while taller varieties can soften a fence or hide utility areas. Design references such as garden styling ideas can help you combine foliage colour, pot shapes and hard landscaping with newly propagated plants.

Water and feed after replanting

Water every division thoroughly immediately after planting, allowing moisture to reach the full root zone. For the first few weeks, check the soil with a finger rather than watering automatically. It should remain lightly moist but never permanently soggy. Once new growth appears, gradually extend the interval between watering so the roots explore the surrounding soil.

The amount required will vary with soil and climate. Sandy Perth gardens may need more frequent checks because water drains quickly, while heavy clay in parts of Melbourne or Canberra may hold moisture for longer. Plants in containers dry out faster than those in the ground, and divisions planted beside hot paving may require extra protection during their first summer.

Australian water restrictions differ between states, councils and utilities, so follow the current rules for your area. Some districts limit sprinkler use on particular days or times, while hand watering and drip irrigation may have separate conditions. Watering early in the morning usually reduces evaporation and gives foliage time to dry.

Do not rush to fertilise newly divided plants. A light application of a controlled-release fertiliser during active growth can be useful once the divisions show signs of establishment, but excess nitrogen may produce soft leaves and weak stems. Compost mixed into the planting area is generally enough at first, especially in soil that already supports healthy garden growth.

Maintain the new clumps through the seasons

Keep an eye on the divisions during their first growing season. Temporary leaf browning is common because the roots have been disturbed, but a collapsing crown, foul smell or persistently wet soil indicates a drainage problem. Remove damaged leaves with clean secateurs and improve airflow around the base.

Many grasses benefit from an annual tidy-up rather than constant trimming. Deciduous varieties can be cut back near the end of winter before fresh shoots emerge. Evergreen types, including lomandra and dianella, are usually better combed through by hand and selectively pruned. Avoid cutting all evergreen foliage to ground level unless the species specifically tolerates it.

Watch for pests such as grasshoppers, snails and fungal problems in dense, damp growth. Good spacing and careful watering reduce many issues. If a plant is suspected of being invasive or declared under state biosecurity or weed legislation, do not share divisions until its status is confirmed. Rules vary across Australia, and unwanted plant material should be disposed of through the appropriate council green-waste service rather than dumped.

Replanting is also a useful opportunity to correct garden problems. Move a grass away from a hot wall, improve drainage in a low spot or replace a struggling specimen with a variety better suited to local conditions. Matching the plant to its site is more reliable than trying to compensate for unsuitable light, soil or moisture with extra fertiliser.

Use divided grasses throughout the garden

A single established clump can provide material for several coordinated planting areas. Use shorter divisions beside steps, around letterboxes or along a narrow courtyard bed. Medium grasses work well near outdoor seating because their movement adds privacy without creating a solid visual barrier. Tall varieties can screen a shed or frame a view, provided they do not block windows or interfere with overhead services.

Foliage colour is especially valuable in Australian gardens. Blue-grey forms contrast with dark mulch and sandstone, while lime-green foliage brightens shaded positions. Flowering spikes can attract attention in late summer and autumn, but the seed heads also provide winter structure. Leave them standing through the cooler months if they remain attractive and cut them back before spring growth begins.

In smaller gardens, growing divisions in containers gives you control over spread and makes it easier to move plants away from harsh afternoon sun. Choose pots with drainage holes, use a quality Australian potting mix and avoid placing containers where reflected heat from concrete will scorch leaves. Raise pots slightly so excess water can escape freely.

Divide with a purpose: rejuvenate crowded plants, repeat a successful design or share healthy material locally where regulations permit. Set aside a weekend during mild weather, prepare every planting spot first and label unfamiliar varieties. With consistent moisture and sensible spacing, the new clumps will settle into the landscape and begin providing texture, shelter and seasonal interest.

Give your established grasses room to thrive, then use their strongest outer sections to renew tired beds and fill empty spaces. Gather the tools, check your local watering and biosecurity requirements, and plan the planting positions before lifting the first clump. A careful division now can create a resilient, attractive garden feature for many seasons.