Ornamental Grass — How to Grow Ornamental Grass in Australia

☀️ Sun

Full Sun

💧 Water

Low

↔ Spacing

60cm apart

↕ Height

Up to 80cm

📅 Harvest

365 days

Growing Guide

Plant Pennisetum in spring (September to November) when soil temperatures have warmed, giving plants a full growing season to establish before winter. In subtropical regions, planting can also occur in early autumn (March to April) to avoid harsh summer heat stress on new transplants.

1. Soil Preparation: Pennisetum thrives in well-drained soils. Dig in a small amount of compost or aged organic matter before planting, but avoid overly rich soil — lean conditions actually promote better flowering and compact growth.

2. Planting: Space plants 60–90 cm apart depending on variety. Plant at the same depth as the nursery pot and water in well with a seaweed solution to reduce transplant shock.

3. Watering: Water regularly for the first 6–8 weeks until established. Once settled, water deeply but infrequently — approximately every 1–2 weeks during summer, reducing significantly in cooler months. These grasses are excellent performers in water-wise gardens.

4. Feeding: Apply a slow-release fertiliser in early spring as new growth emerges. A single annual application is generally sufficient.

5. Mulching: Apply a 5–7 cm layer of organic mulch around the base to conserve soil moisture, suppress weeds, and protect roots during temperature extremes.

6. Seasonal Care: Deadhead spent flower spikes if self-seeding is a concern, particularly with Pennisetum setaceum, which is considered invasive in some Australian states. Always check local regulations before planting.

🤝 Good Companions

Pennisetum pairs beautifully with Salvia Echinacea and Agapanthus as these flowering perennials provide bold colour contrasts that complement the grasses' fine texture and feathery plumes. Lomandra and Westringia also make excellent companions sharing similar water-wise requirements and creating cohesive low-maintenance Australian native or naturalistic garden schemes.

❌ Avoid Planting With

Avoid planting Pennisetum alongside moisture-loving plants such as ferns Canna lilies or bog plants as the dry free-draining conditions that fountain grasses require will be unsuitable for these companions. Pennisetum setaceum in particular should not be planted near bushland or natural reserves in Queensland New South Wales and Western Australia due to its recognised invasive potential.

🐛 Pests & Diseases

Pennisetum species are generally robust and pest-resistant in Australian gardens, though aphids and mealybugs can occasionally cluster on new growth or within the crown during warm, humid periods — a strong blast of water or an application of neem oil spray will effectively manage infestations. Fungal issues such as leaf rust or crown rot may occur in poorly drained soils or during prolonged wet weather; improving drainage and avoiding overhead watering are the best preventative measures. In humid subtropical regions, keep the centre of clumps open by dividing regularly to improve air circulation and reduce disease pressure.

🌱 Fertilising

Apply a balanced slow-release granular fertiliser (such as an NPK 8:4:8 formulation) to the soil surface in early spring as new shoots emerge, following label rates carefully to avoid excessive leafy growth at the expense of flowering. A light top-dressing of compost in autumn can help maintain soil structure and organic matter levels without over-stimulating the plant during its dormant or semi-dormant period.

✂️ Pruning & Training

Cut Pennisetum clumps back hard in late winter to early spring (August to September) before new growth begins, reducing the plant to approximately 10–15 cm above ground level using sharp secateurs or hedge shears. This annual hard prune removes old, tatty foliage, rejuvenates the clump, and encourages a fresh flush of tidy new growth and prolific flowering through summer and autumn.

🔬 Propagation

The most reliable method of propagation is division — in early spring, lift established clumps with a garden fork, split them into sections using a sharp spade, and replant divisions at the same depth with refreshed compost-amended soil. Pennisetum can also be grown from seed sown in spring into seed-raising mix at 20–25°C, though named varieties and coloured cultivars such as 'Rubrum' will not come true from seed and must be propagated by division to retain their distinctive characteristics.

🗓 When to Plant

Spring Summer Autumn Winter

🌾 Harvest

All

🌏 Australian Climates

Temperate Cool Temperate Mediterranean Subtropical Arid