Care and Maintenance Advice for Ornamental Grasses

Ornamental Care and Maintenance

Ornamental grasses can add vibrant accents to your existing plants and have a multitude of purposes for our gardens.  They can be used to add textures to flower beds and borders, create edging, soften hardscapes or grow a prairie garden.  With a full spectrum of colour varieties available, most grasses are easy to care for and highly versatile.  Like all garden plants, proper selection for gardening conditions and choosing which species complement each other will add colour and vibrant texture that flows with the breeze.

These grasses are all relatively low maintenance, free of disease and pests and add will add a distinctive character and personality to your garden.

Ornamental Grass Planting Advice

Our nursery only grows resilient and hardy potted varieties and can be planted year round as long as the soil is not frozen or waterlogged.  If planting in late autumn it is best to plant before the first frost.

Plant Spacing 

As a good rule of thumb is to space plants proportionate to how tall they are at maturity.  For example, if the plant will reach 1 meter at maturity, plant them 1 meter apart.  For larger varieties like Cortaderia (Pampas) place plants 2 m (6ft) apart.  

  • Plant height 50-100cm (20-40in)   -recommended 6 plants per linear meter
  • Plant height 100-150cm (40-60in) -recommended 4 plants per linear meter
  • Plant height 150-200cm (60-80in) -recommended 3 plants per linear meter
  • Plant height 200-250cm (80-100in) -recommended 2 plants per linear meter
  • Plant height 250-300cm (100-120in) –recommended 1-2 plants per linear meter
  • Plant height 300-350cm (120-140in) –recommended 1-2 plants per linear meter 

Ground Preparation

  1. It is always best to measure twice and cut once, so use planning line and canes to plot out your location. Start by removing all turf above the immediate area before planting.
  2. Remove all vegetation from the immediate planting area before you begin digging.
  3. Using a gardening fork, till up the soil thoroughly twice as deep as container the plant was shipped in. If available, you can also use a petrol powered tiller. This is important as uncultivated soil can restrict plant growth and not let the roots establish. Make sure and remove any large rocks.

Day of Planting

Plant your new Ornamental grass

  1. Place a landscaping tarp parallel to the planting area and dig an area twice as wide as the shipping container and just as deep, place soil on the tarp after removal. If necessary, use the container itself as a guide.  For Cortaderia (Pampas) Dig holes that are 3 times as deep and wide as the root ball to encourage spreading.
  2. Mix the native soil that is to be backfilled 1-1 with Planting Compost. If you have heavy soil and drainage is a problem, consider amending with Horticultural Gravel.
  3. Carefully remove the plant from the pot and break up the bottom edges of the rootball taking care to unfurl and tease out the roots from the base so that they will establish in the soil. Tap the side of the pot with your hand if the rootball is being stubborn and will not remove easily.  Then gently place the plant upright into the hole, packing the surrounding soil around the root ball to keep the plant in the desired position make sure to plant at the root line.
  4. Water the soil around the plant thoroughly, make sure the soil is very moist but don’t use so much water that puddles form. Water bi-weekly for the first month and weekly for the next two months.  Subsequent watering should only be necessary during extended dry spells.

Container Planting

  1. Make sure the pot is wide enough to accommodate arching grass blades and has proper drainage. A lighter, unglazed pot will evaporate excess moisture better than darker, glazed pots.
  2. Cover the drainage holes with a screen to prevent clogging. Add a bottom layer of Horticultural Gravel but make sure to cover with a layer of soil so the roots do not directly touch the gravel.
  3. Use a 1-1-1 mix of Planting Compost, Horticultural Gravel, and native topsoil to ensure the plant has proper nutrition and drainage.
  4. After removing the plant from the shipping container, plant at rootball depth and pack the surrounding area with 1-1-1 mix. Pack firmly enough for positioning, but not so tight that root growth is restricted.
  5. Water thoroughly after planting until water comes out of the drainage holes but do not waterlog.

Ornamental grasses are very hardy and will establish strong roots if planted properly adding charm and character to your garden.

Ornamental Grass Trimming Advice

There are two main categories of Ornamental Grasses; evergreen and deciduous.  While deciduous grasses will need to be cut back annually, evergreens will just need to be trimmed up.  

Deciduous Grasses

  • Some varieties like Cespitosa Goldtau need to be trimmed all at once at 3cm (1in) above ground level before growth start in early spring (mid-March to April). Prune Miscanthus at the same time, but individually remove the shoots with secateurs so as not to sever the newly forming green shoots.
  • While Stipa Tenuissma is classified as deciduous, it will tend to have evergreen traits in some gardens. If there are low amounts of dead material building up, simply comb out the loose foliage as you would an evergreen.  If it takes deciduous traits and foliage dies off uniformly, fully cut back in spring. 

Evergreen Grasses 

  • Do not cut back evergreen varieties like Carex (Sedges) all at the same time. Cut off spent stalks and individually remove diseased or unsightly leaves.
  • Cortaderia (Pampas) does benefit from hard pruning in early spring.  Cut back vigorously, but take care not to damage new growth.  Wear eye protection and gloves, leaves can be sharp.  Use loppers to sever stubborn stems.

Ornamental Grass Watering Advice

Automatic irrigation systems are preferred.  Water your new plants bi-weekly for the first month after planting and weekly for the next two months.  If in doubt, use the finger test and push your finger into the ground.  If it is dry, add water and if it is moist do not. Remember you want the ground moist but not so much that puddles form.  Subsequent watering should only be necessary during extended dry spells, unnecessary watering can leave to droopy, unsightly form.

Container based plants will require regular watering but allow the soil to dry out to a depth of several inches before watering again.

Ornamental Grass will prosper with a little effective initial watering allowing the root system to establish and the plant to thrive.

Ornamental Grass Feeding Advice

Unlike other perennials and shrubs, ornamental grasses do not normally require fertilizer, and too much nitrogen can deter foliage growth and give them a floppy, dishevelled look.  If you feel feeding them is necessary, choose a balanced, slow release fertilizer at ½ strength in early spring.

For container based plants, a spring fertilizer treatment is necessary since they have limited nutrition.  A balanced 10-10-10 fertilizer is best, follow manufacturer’s instructions.

Your new Ornamental Grass will require little feeding to thrive and prosper in your garden.