How to prune Ornamental grasses the easy way

Ornamental grasses are some of the lowest-maintenance plants you can grow, with one exception. Once a year they need cutting back or tidying, and getting the timing and the method right for each type makes the difference between a fresh, upright clump in June and a tired, brown thatch that never quite recovers. It is the one job I would ask you to get right with grasses, because they forgive most other mistakes.

I leave every grass in my Exploding Atom Garden standing through the winter. On a frosty morning the seed heads of the Deschampsia and Pennisetum catch the low sun and hold the frost, the birds pick through them for seed, and the dense clumps shelter overwintering insects. Then, usually in the last week of February, I get the sickle out and cut the lot back in an afternoon. This guide walks you through exactly how I do it, grass by grass.

If you are still choosing which grasses to grow, my guide to the best ornamental grasses for UK gardens covers my 13 top picks for small and large gardens, and every grass in this guide links back to its entry there.

🛒 The tool that halves the time this job takes is a serrated Japanese grass sickle, which slices through a gathered clump of dead stems in two or three pulls.

When to Cut Back Each Grass: Quick Guide

Here is when and how to cut back the ornamental grasses I get asked about most. Timings are for an average UK garden. In the south and in mild coastal gardens you can start a week or two earlier, and in the north or in cold, exposed gardens it pays to wait until March.

What Happens If You Don’t Cut Back Ornamental Grasses?

Nothing dramatic happens in the first year, which is why so many people leave it. A deciduous grass that is not cut back simply pushes its new shoots up through last year’s dead stems. The fresh green growth is hidden inside a skirt of straw-coloured thatch, so the clump looks tired and scruffy all summer, and the flowering stems often flop outwards because they are leaning on dead material.

Leave it for two or three years and the problems build. The dead thatch shades the crown, holds water against it and gives slugs somewhere to hide, so the centre of the clump starts to die out and you are left with a ring of growth around a bald middle. At that point cutting back alone will not fix it, and the clump needs lifting and dividing.

Evergreen grasses are more forgiving. A Carex or Festuca that is never tidied keeps growing, but the dead leaves collect at the base and the plant looks increasingly brown and matted. Ten minutes combing it out each spring keeps it looking fresh.

When to Cut Back Ornamental Grasses in the UK

For most grasses in most UK gardens, the best time to cut back is late February to the end of March, just as the plants start to wake up and before the new shoots are more than a few centimetres tall. Cut too early and you lose the winter display and expose the crown to the worst of the frost and wet. Cut too late and you end up slicing the tops off the fresh green shoots, which leaves the clump with brown, blunt tips for the rest of the year.

The easiest way to judge it is to part the clump with your hands and look at the base. If you can see green shoots pushing through, it is time. I usually start on the last weekend of February with the Calamagrostis, which wakes up earliest, and finish with the Pennisetum in March, which is always the last to stir.

Cool season and warm season grasses

This difference in timing comes from where the grasses originate. Cool season grasses such as Calamagrostis, Deschampsia, Festuca and Stipa grow from early spring and flower in early summer, so they need cutting or tidying earlier. Warm season grasses such as Miscanthus, Panicum and Pennisetum come from hotter climates, do not start growing until the soil warms in late spring and flower from late summer, so you can safely leave them a few weeks longer.

Can you cut back ornamental grasses in autumn?

You can, and some gardeners do so for a tidy garden over winter, but I would not. Cutting in October or November removes the winter structure, takes away food and shelter for birds and insects, and leaves the cut crowns open to rain sitting in them all winter. In heavy, wet soil that is a recipe for crown rot, particularly with Pennisetum. The only grasses I cut in autumn are ones that have collapsed into a soggy heap after a storm, and even then I only remove the fallen stems.

If you want a neater look through winter without losing the benefits, try tying tall deciduous grasses into a loose wheatsheaf with garden twine. It keeps them upright, stops them flopping across paths and still leaves the seed heads for the birds.

Can you trim ornamental grasses in summer?

Generally not. Cutting a deciduous grass in summer removes the foliage it needs to build up energy and usually takes the flower stems with it. The exceptions are tidying jobs: you can pull out dead leaves from Carex and Festuca at any time, and a Stipa tenuissima that has flopped open after heavy rain in early summer can be cut back by about half and will regrow quickly.

Deciduous, Evergreen or Semi-Evergreen? Identify Your Grass First

Before you cut anything, work out which group your grass belongs to, because the method is completely different. Cut a deciduous grass hard and it bounces straight back. Cut an evergreen grass to the ground and you can set it back by a year or kill it outright. The most common grasses problem I am sent every spring on the forum is a photo of a Stipa gigantea or a Carex cut to stubble, with the question of why it is not growing back.

If you do not know what your grass is, you do not need a book. Look at it in January. If the whole clump has turned straw-coloured, beige or orange, it is deciduous and gets a hard cut. If it is still mostly green, blue or bronze, it is evergreen and gets a tidy. If it is half and half, it is semi-evergreen, and you treat it as an evergreen unless it looks tired.

Deciduous grasses

Most of the tall flowering grasses fall into this group, including Miscanthus, Calamagrostis, Panicum, Pennisetum, Molinia and Hakonechloa. Their foliage dies off in autumn but stands through winter, and the plant regrows from the crown each spring. These are the ones that need cutting right back every year.

Evergreen grasses

Evergreen grasses keep living foliage all year. This group includes most Carex, Festuca glauca, Stipa gigantea, Anemanthele lessoniana, Luzula and Pampas grass. Strictly speaking, Carex are sedges and Luzula are woodrushes, but they are sold and grown alongside grasses and treated the same way. Apart from Pampas, these only need the dead material removing.

Semi-evergreen grasses

In the mild, damp UK climate a handful of grasses sit in between, holding some green foliage in a mild winter and dying back in a cold one. Deschampsia cespitosa and Stipa tenuissima are the two you are most likely to have. Comb them out in spring, and only cut them back hard if they are looking brown and tired all the way through.

Tools for Cutting Back Ornamental Grasses

You do not need much kit, and the right tool depends mostly on how many grasses you have. For a couple of clumps, secateurs are fine. For a border full of Miscanthus, you will want something faster, or you will still be out there at teatime.

A serrated grass sickle or bread knife

A serrated Japanese sickle is my first choice for deciduous grasses, because the saw-tooth edge grips the stems instead of sliding off them.

Before I owned one, I used an old serrated bread knife from the kitchen, and it still works well if you have nothing else. Grab the clump like a ponytail and saw through the base in a few quick strokes. I have said it before, and I will keep saying it: think Uma Thurman against the Crazy 88 in Kill Bill, only with a lot less mess.

Secateurs and shears

Sharp secateurs are best for evergreen grasses, where you are snipping out individual dead stems, and for small deciduous grasses such as Hakonechloa. Keep them clean and sharp, because blunt blades crush grass stems rather than cutting them. My guide to the best secateurs covers the pairs I use, and my secateur sharpening guide shows how to keep them cutting cleanly. Hand shears are useful for trimming Festuca into a neat dome.

A cordless hedge trimmer for big drifts

If you have a prairie border or a long run of Miscanthus, a cordless hedge trimmer turns an afternoon into half an hour. Tie the clump first so the stems stay together, then run the trimmer through the base. It is how I tackle the largest clumps, and my best cordless hedge trimmers guide compares the models I have tested.

Gauntlet gloves and eye protection

A pair of long-cuff gauntlet gardening gloves protects your wrists and forearms, which are the parts that get cut when you reach into a clump.

Grass leaves have sharp, serrated edges, and Pampas grass in particular will slice skin like paper. Wear long sleeves, and wear safety glasses when you are working with tall grasses, since a flicked leaf blade to the eye is painful and easily done. My gardening gloves guide covers the pairs I rate.

A hand rake or grass comb

A small hand rake for grasses pulls dead thatch out of evergreen clumps far faster than your fingers.

A spring-tine rake does the same job on bigger clumps and is useful for clearing up the cut stems afterwards. Add a trug or a tarpaulin to drag the clippings to the compost heap, and some garden twine or a couple of bungee cords for tying clumps before you cut.

How to Cut Back Deciduous Grasses Step by Step

This is the method I use for Miscanthus, Calamagrostis, Panicum, Pennisetum and every other grass that dies back over winter. It works for a single clump by the patio or a whole border.

1. Check for new shoots. Part the clump and look at the base. You want to cut before the new green growth is more than 5cm or so tall.
2. Tie the clump. Wrap garden twine or a bungee cord around the middle of the clump. On large grasses this keeps all the stems together so they come away in one bundle instead of scattering across the border.
3. Grab and cut. Hold the bundle firmly just above where you want to cut, then saw through the stems with a sickle, bread knife or hedge trimmer about 10 to 15cm above the ground.
4. Tidy the stubble. Trim any long stragglers level, keeping the blades above the new shoots. Leaving a short stubble protects the crown from frost and rain sitting in it.
5. Rake out the debris. Pull the loose dead material out of the base with your fingers or a hand rake, so light and air can reach the new growth.
6. Compost the stems. Chop or shred the stems before they go on the heap, because long grass stems take a long time to break down whole.

How low you cut depends on the grass. I leave around 10 to 15cm on big grasses such as Miscanthus and Panicum, and go lower, to 5cm or so, on small ones such as Hakonechloa. Some specialist growers cut right to the ground to give the new shoots a clear run, and that works in free-draining soil, but in heavier, wetter ground I have found a short stubble stops water sitting in the crown and rotting it.

The cut stems are worth keeping. Long, dry Miscanthus and Calamagrostis stems can be bundled and tucked into a quiet corner as an instant bug hotel, or chopped and used as a mulch. If you have a lot, a garden shredder turns them into compost material in minutes.

How to Tidy Evergreen Grasses

Now the technique changes. Put the sickle down, because evergreen grasses need a gentle tidy, not a haircut. The aim is to remove the dead leaves and old flower stems while leaving all the living foliage intact.

Wait until early spring, when the plant is starting to grow. Put on gloves and run your fingers through the clump from the base outwards, like combing tangled hair. The dead leaves come away easily, and the living ones stay put. For larger clumps, a hand rake does the same job faster. Any dead leaves still firmly attached can be snipped off individually at the base with secateurs.

Remove old flower stems by cutting them right down at the base, taking care not to catch any of the new flower spikes coming through. Then stand back, look at the shape, and trim any brown tips with scissors or shears if you want a neater finish.

If an evergreen grass has turned mostly brown after a hard winter, you can cut it back harder in spring, to around a third of its height, once you can see new growth. Most will recover, but it takes the whole summer, and a very old, tired clump is usually better lifted, divided and replanted.

How to Cut Back Pampas Grass

Pampas grass, Cortaderia selloana, is the one evergreen grass that benefits from a hard cut every year, and it is also the most unpleasant grass to prune. The leaves are razor-edged, the clumps are huge, and old plants carry years of dead thatch in the middle. It has come back into fashion thanks to dried plumes, and I am now asked about it far more than I was ten years ago, often by people who have inherited a monster in a front garden.

When to cut back Pampas grass

Cut Pampas back in late February or March, before the new leaves start growing strongly. Leave the plumes on through winter for the display, and cut before the fresh growth gets tall, so you are not slicing through it.

How to cut back Pampas grass safely

For Pampas, a pair of long-handled bypass loppers keeps your hands and face away from the leaves while you cut through the thick old stems.

1. Dress for it: gauntlet gloves, long sleeves and safety glasses.
2. Cut off the old plumes first and set them aside for drying or composting.
3. Tie the foliage into a bundle with rope at around waist height.
4. Cut the whole bundle down to around 30cm with loppers, a pruning saw or a hedge trimmer. Go lower if no new growth is showing yet.
5. Rake or comb out the dead thatch from the centre of the clump with a spring-tine rake.
6. Clear away the debris and check the clump for hibernating hedgehogs before you rake the base.

Never burn Pampas grass to clear it. It is an old trick that still gets passed around, but it can kill the crown, and the dry thatch at the base of a Pampas clump is exactly where hedgehogs and other small mammals shelter over winter.

What happens if you don’t prune Pampas grass?

An unpruned Pampas grass builds up a thick mat of dead leaves around a green outer layer. Each year the clump gets wider and browner in the middle, the plumes get fewer and shorter, and the whole plant becomes harder to deal with. If yours has got to that stage, cut it back hard in spring, and if it is too big for the space, dig out sections from the edge with a sharp spade to reduce its size. For smaller gardens, the compact Cortaderia selloana ‘Pumila’ gives the same look at around half the size.

Grass by Grass: How to Cut Back Popular Ornamental Grasses

The general rules above cover most grasses, but each one has its own quirks. These are the grasses I grow and plant most often in client gardens, with the timing and method I use for each. Every one of them also has an entry in my best ornamental grasses guide if you want the growing details.

Miscanthus

Miscanthus is the classic deciduous grass and the easiest to cut back. Leave the feathery plumes up all winter, then cut the whole clump to 10 to 15cm in late February or March. Big, established clumps have stems as tough as bamboo, so this is where a sickle or hedge trimmer earns its keep. Zebra grass, Miscanthus sinensis ‘Zebrinus’, and ‘Morning Light’ are treated exactly the same way. See Miscanthus ‘Morning Light’ in my top grasses guide.

Calamagrostis ‘Karl Foerster’

Feather reed grass is a cool season grass, so it wakes up earlier than most. It is the first grass I cut each year, usually in mid to late February, because by March the new shoots are already well up and easy to damage. Cut it to about 10cm. The upright stems stay standing through the worst of the winter weather, which is why I use it so often in designs, including the border behind me in the photo below. Calamagrostis ‘Karl Foerster’ in my top grasses guide.

Pennisetum ‘Karley Rose’

Fountain grasses are warm season grasses and slightly less hardy than Miscanthus, so they are the last ones I cut. I grow ‘Karley Rose’ in my Exploding Atom Garden, and I leave its old foliage in place until late March or even early April, because the dead leaves act as a blanket over the crown during cold, wet spells. Cut to around 10cm once the worst of the frosts are over. Pennisetum ‘Karley Rose’ in my top grasses guide.

Panicum virgatum

Switchgrass holds its shape and autumn colour well into winter and does not start growing until late spring, so there is no rush. Cut it back to 10cm in March. Panicum ‘Shenandoah’ in my top grasses guide.

Molinia caerulea

Purple moor grass does half the job for you. By midwinter the flower stems often snap away from the base on their own, and you can simply pull them out. Cut whatever is left to 5 to 10cm in late winter. Molinia ‘Edith Dudszus’ in my top grasses guide.

Hakonechloa macra

Japanese forest grass is a small deciduous grass for shade that turns copper in winter. Cut it back to about 5cm in late February or March, before the new shoots appear. It is slow to establish, so be careful not to damage the crown. Hakonechloa ‘Aureola’ in my top grasses guide.

Deschampsia cespitosa

Tufted hair grass is semi-evergreen and one of my favourites for winter structure. In February or March, cut the old flower stems out at the base and comb the dead leaves from the clump. If it looks brown all the way through after a hard winter, cut it to 10cm and it will regrow. Deschampsia cespitosa in my top grasses guide.

Stipa tenuissima (Mexican feather grass)

Now officially called Nassella tenuissima, this is the grass I get asked about most, because it is in so many front gardens. It is semi-evergreen, so in March or April, run your gloved fingers through it from the base outwards and pull out the loose, dead growth. It comes away in handfuls. Only cut it back hard if it has gone brown and flat all the way through. It is short-lived and self-seeds freely, so rather than trying to rescue a tired old plant, I let the seedlings replace it. Stipa tenuissima in my top grasses guide.

Stipa gigantea (Giant oat grass)

Giant oat grass is evergreen, and this is the grass most often cut down by mistake. Leave the foliage alone. In late winter, cut last year’s tall flower stems out right at the base, then comb the dead leaves out of the clump. Be careful in April, when the new flower spikes start to push through. Stipa gigantea in my top grasses guide.

Carex

Most garden Carex, including the bronze and orange forms such as Carex comans and Carex testacea, are evergreen. Never cut them back hard. Comb out the dead leaves in spring, and snip off any brown tips if you want a tidier plant. Carex ‘Comans Bronze’ in my top grasses guide.

Festuca glauca (Blue fescue)

Blue fescue collects dead leaves at the base, which turns the clump grey and shabby. In spring, comb the dead material out with your fingers, then trim the tips with shears to a neat dome if you like. Old clumps go bald in the middle after three or four years, so lift and divide them or replace them. Festuca glauca in my top grasses guide.

Luzula nivea (Snowy woodrush)

Snowy woodrush is an evergreen for dry shade that only needs the dead leaves pulling out in spring. Cut the old flower stems out at the base once they fade.

After Cutting Back: Mulching, Feeding and Dividing

Once the grasses are cut and the debris cleared, weed around each clump and spread a 5cm layer of garden compost or well-rotted bark around them, keeping it just clear of the crowns. It keeps weeds down while the new growth fills out. My mulching guide covers what to use.

Established grasses rarely need feeding. Most come from poor, open grasslands, and rich soil makes them grow soft and flop. If a grass is growing on very poor sand or has struggled for a year or two, a light scattering of a balanced slow-release feed in spring is plenty.

When to divide ornamental grasses

Spring, right after cutting back, is the best time to divide grasses, because the clump is short and easy to handle. If a grass has a dead, bald centre, or it has simply outgrown its space, dig it up, slice it into sections with a sharp spade, throw away the dead middle and replant the healthy outer pieces. Warm season grasses such as Miscanthus and Panicum are best divided in late spring, once they are growing. My guide on how to divide plants shows the technique step by step.

Grasses are usually planted with late summer perennials, and the two are cut back at around the same time. My guide to pruning herbaceous perennials covers the rest of the border, and my prairie border guide shows how I combine the two. The video below walks through cutting back the perennials.

Common Mistakes When Cutting Back Grasses

Most grass problems I see come down to one of a handful of mistakes, and all of them are easy to avoid once you know about them.

Cutting evergreen grasses to the ground

This is the big one. Evergreen grasses do not regrow from a hard cut the way deciduous grasses do, and some never recover. If you are not sure which type you have, comb it out first. If there is a lot of green left in it, stop there.

Cutting too late

Leave it until May and the new shoots are already 20cm tall inside the clump. Cut then and you take the tops off the new growth, which leaves blunt brown tips on every leaf for the rest of the year.

Cutting in autumn in wet soil

A cut crown sitting in cold, wet soil all winter is prone to rot, particularly with Pennisetum and on heavy clay. Leave the old growth on until late winter to act as a raincoat for the crown.

Working without gloves

The edges of grass leaves are fine, sharp and serrated. One bare-handed grab of a Miscanthus clump is usually enough to teach anyone this lesson, and Pampas is worse.

Burning grasses to clear them

Burning damages the crown and kills any wildlife sheltering in the base. Cut, rake and compost instead.

If you are working through the rest of the garden too, my winter pruning guide covers what else to cut back at this time of year and what to leave alone.

Ornamental Grass FAQs

What happens if you don’t cut back ornamental grasses?

Deciduous grasses that are not cut back push new growth up through last year’s dead stems, so the clump looks brown and scruffy all summer and the stems tend to flop. Over two or three years the dead thatch smothers the crown and the centre of the clump starts to die out. Evergreen grasses cope better but gradually become matted with dead leaves.

When should I cut back ornamental grasses in the UK?

Cut back deciduous ornamental grasses in late February or March, just before or as the new shoots start to appear at the base. Cool season grasses such as Calamagrostis need doing first, and warm season grasses such as Miscanthus, Panicum and Pennisetum can wait until March. Evergreen grasses only need combing out in spring.

How far should you cut back ornamental grasses?

Cut large deciduous grasses such as Miscanthus and Panicum to about 10 to 15cm above the ground, and smaller ones such as Hakonechloa to about 5cm. Leaving a short stubble protects the crown from frost and stops water sitting in it. Pampas grass can be cut to around 30cm. Evergreen grasses should not be cut back hard.

Can I cut back ornamental grasses in autumn?

You can, but it is better to wait until late winter. Leaving grasses standing gives winter structure, provides food and shelter for birds and insects, and protects the crown from wet weather. Cutting in autumn, especially in heavy, wet soil, increases the risk of crown rot.

When should I cut back Pampas grass?

Cut Pampas grass back in late February or March, before the new leaves start growing strongly. Wear gauntlet gloves, long sleeves and eye protection, tie the foliage into a bundle, cut it down to around 30cm with loppers or a hedge trimmer, then rake out the dead thatch. Never burn it.

Should I cut back Stipa tenuissima?

Usually not. Stipa tenuissima, now called Nassella tenuissima, is semi-evergreen, so comb the dead growth out with gloved fingers in March or April. Only cut it back hard if it has turned brown all the way through. It is short-lived and self-seeds, so replacing tired plants with seedlings is often easier than rescuing them.

When should I cut back Miscanthus?

Cut Miscanthus back to 10 to 15cm in late February or March, before the new shoots grow through the old stems. This applies to all Miscanthus, including Zebra grass (Miscanthus sinensis ‘Zebrinus’) and ‘Morning Light’. A serrated sickle or cordless hedge trimmer makes quick work of large clumps.

Do ornamental grasses need feeding after cutting back?

Established ornamental grasses rarely need feeding. Most come from poor grassland soils, and too much fertiliser makes them grow soft and flop. A mulch of compost around the clumps after cutting back is usually enough, with a light slow-release feed only on very poor soil.

Design Borders That Look Good All Year Round

Grasses give a border movement in summer and structure in winter, and knowing how to place them is half the battle. My online garden design courses show you how I plan borders, choose plants for each season and put a whole garden together, using the same approach I use for client gardens. Courses start from £29 and you keep lifetime access.

Summary

Cutting back ornamental grasses is a once-a-year job that takes an afternoon. Identify whether each grass is deciduous, evergreen or semi-evergreen, leave them all standing through winter for the frost, the birds and the insects, then in late February or March cut the deciduous ones back to a short stubble and comb the dead leaves out of the evergreens. Pampas is the one evergreen that gets a hard cut, with plenty of protective gear.

Get that right and your grasses will come back fresh and upright every spring for years. If you are planning to add more to your garden, have a look at my best ornamental grasses for UK gardens and tag me on Instagram with your before and after photos once the job is done.

Happy Gardening!