Care for Ornamental Grasses

We’re sure you’ve noticed that grasses have come a long way since the 1980s invasion of pampas grass. Quickly becoming untameable, and with sharp leaves that could deliver vicious ‘papercuts’, we can’t say that we’re disappointed pampas has gone out of fashion in domestic gardens.  Other grasses, however, have become more popular and valued for their variety. As was recently demonstrated at RHS Chelsea, they are not just for prairie planting schemes and can hold their own in any garden.

Grasses are such a diverse species (or rather, collection of species) that there is one for any position, from dry shade to moist sunlight. Their colours and textures can provide a calm backdrop to more showy plants, and their shimmering height can add movement. Even in autumn and winter, colourful stems or fluffy seed heads offer interest to humans and wildlife. Is there anything more appealing than a frost-encrusted frond, sparkling in the low winter sunshine, especially when the rest of the garden lies dormant?

Here’s our quick guide to approaching the planting and care of ornamental grasses in your garden.

Planting

grass pots

Grasses can broadly be divided into two types: those from cooler climates (such as Stipa, Deschampsia or Festuca) and those from warmer climates (Pennisetum, Miscanthus or Cortaderia, for example).  It’s useful to know which is which in order to plant them at the optimal time.

Grasses from cool climates will prefer to be planted in the autumn, so they are established before the weather warms up.  However, those from warmer climates are best left until later spring, as they will welcome the warmth to establish.

Ornamental grasses will tolerate a wide range of positions so check the plant label. In general, however, most will prefer a sunnier position with well-drained soil.  For this reason, grasses can also work well in pots.

Feeding

Grasses do not need highly fertile soil or much additional feeding.  Too many nutrients can encourage lots of over-lush foliage but fewer flowers. If you want to give your grasses a top-up, consider one application of a balanced fertiliser in the spring, as they start to show new growth.

grassesCutting Back

As we’ve already said, many grasses look magnificent over winter and provide shelter for wildlife so we would urge everyone not to cut back grasses too early. 

Grasses are either deciduous (their leaves turn to ‘straw’ rather than fall off) or are evergreen. Please check your plant label as this will affect how and when you cut back. 

In general, smaller evergreen grasses probably do not need cutting back; just trim off any brown leaves or spent seedheads as and when.  A larger evergreen (if you do still own a pampas grass, for example) may benefit from a really hard cutting back in spring, to refresh the plant; just watch out that you don’t cut any new growth (and wear protective gear).

Deciduous grasses can be left until the spring for pruning (unless they look particularly unsightly) as the old stems will protect the new growth.  For a smaller plant, you may prefer to don a pair of sturdy gardening gloves and gently ‘comb’ the plant through with your fingers; this will remove loose dead matter and leave the crown and any new growth unharmed.  For larger plants or sturdier stems, it may be easier to go in with secateurs or loppers, reducing the height to about half first, so you can then see better the old growth to be removed.

Remember to save the dried stems to add drama and height to flower arrangements, or to spray gold for Christmas decorations.

Propagating

ornamental grass

One of the best ways to get new plants is by division.  When an ornamental grass has outgrown its space, think about digging it up and dividing it, literally by putting a spade through it.  As with planting, think about whether your grass is a cool climate or warm climate variety.  Cool climate varieties will prefer being divided in colder weather (late winter or early spring) whereas warmer climate varieties will do better in later spring, when they are actively in growth.

You can also collect grass seeds; indeed some grass seeds will sow themselves profusely around your garden if you let them!  Collect ripe seed heads (or well-developed flowers that can be left to ripen indoors). You can then either sow them immediately (at a cool temperature) or store them to plant in the spring.  Some grasses can be slow or tricky to germinate so it’s worth checking the advice specific to your variety.  Our plant expert, Steve, can help with that

Pests and Problems

grass

Ornamental grasses are generally fairly problem free; they are more likely to suffer because they are in the wrong position or having become over-crowded than from any specific pest or disease.  Rust, for example, is often a sign of congested clumps so dividing to allow better air circulation can help resolve this.  Non-flowering in usually flowering grasses may be caused by insufficient light, so consider moving the plant to a sunnier spot or cutting back any overhanging plants. 

If you live in an area where rabbits can be a problem, be warned that they may also take a shine to your grasses. Without resorting to extreme pest control, perhaps planting ‘sacrificial’ or decoy plants will hold the bunnies off long enough for your grasses to establish.

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