How to cut down ornamental grasses

What’s the best tool to cut down large ornamental grasses?

Ornamental grasses have grown in popularity over the past several years primarily because they are easy to grow and create four seasons of interest in the garden. The problem for many of us comes when it’s time to cut the larger grasses down in the spring or fall.

The larger clumping grasses, like varieties of Pampas grass (Cortaderia) and my favourite, Maiden grass (Miscanthus), are delicate when first planted, but over the years the clumps grow, the grass stems thicken up and cutting them down can become very difficult work. Even the smaller grasses in my garden, fountain grass (Pennisetum), little bluestem (Andropogon gerardii), and Northern Sea Oat grasses (Chasmanthium latifolium) are a chore to cut back in the spring.

Be sure to check out my posts on the Three best grasses for a shade or woodland garden and the Best Ornamental grasses for sun and shade. You might also be interested in my post on why we should leave our grasses up all winter.

For years, I used simple secateurs to cut down the dried grasses one stem at a time each spring. The job took hours and, although I wore gloves, I was usually left with scratched knuckles and very sore hands.

The job became such a burden that I put it off as long as possible often resulting in having to cut the stems higher than I wanted because the new grasses were already beginning to put on growth.

I am getting older, and cutting back the grasses is getting more difficult each year. It was time to look for an alternative.

This Miscanthus Sinensis is a real winner in the fall with it’s elegant seed heads. Cutting it down in early spring, however, can be difficult without the right tools. An electric headge trimmer (pictured below) made short work of the dried stems th…

This Miscanthus Sinensis is a real winner in the fall with it’s elegant seed heads. Cutting it down in early spring, however, can be difficult without the right tools. An electric headge trimmer (pictured below) made short work of the dried stems this fall.

Last year we used a combination of the secateurs and a weed eater with a string to cut through the grasses. Although we eventually got the job done, it wasn’t easy or quick. A weed eater with a blade is often suggested rather than a string, but I prefer not to work with a spinning blade whirling around my toes. The grasses are replaceable, my toes are not.

This spring cutting back our grasses took a giant leap forward. The solution: I decided it was time to get smart and use an electric hedge trimmer to do the heavy work for me. This cordless model from Gardener’s Supply Company will make the job a whole lot easier.

This spring, the electric hedge trimmer not only cut the grasses down with great ease, it enabled me to cut the stems shorter, giving the garden a cleaner look and opening up the clumps to more sunshine leading to better early-spring growth. It handled the tough, thick stems as well as the smaller more dense grass stems with ease. An added bonus to my spring clean up was that the hedge trimmer was powerful enough to cut down a number of unwanted shrub and sucker growth saplings that were slowly taking over an area of the garden.

I like to cut my grasses down in the spring to benefit from the look of their lovely dried stems all winter and, more importantly, to give insects a safe place to spend the winter. Birds too benefit from the grasses giving them an opportunity to feed on the seeds and any insects or insect eggs they can find hiding in the dried grass stems.

The dried stems can also be cut down in fall, but you would miss out on the delicate snow-covered branches and deprive insects and birds of habitat and potential feeding locations.

This spring, the task of cutting down the grasses was so easy that I can’t ever imagine cutting the grasses with any other tool after using the electric hedge trimmers.

Not only did it make taking down the larger stems a joy, but it cleaned up my smaller ornamental fountain grasses, northern sea oats and little bluestems in mere seconds.

In total, my wife and I cut down about 15 ornamental grasses in less than an hour. The same task using garden secateurs would have taken about three hours and left me with sore, cut-up hands from the sharp, dried, dead stems, as well as a very sore back.

Before you actually cut the grasses down – especially large clumps – it’s a good idea to tie them off with string. Then, when you cut the dead stems off, they are contained nicely in a tight compact form by the string and are easy to carry to the back compost area.

I like to pile them into my large gardening bag or Gorilla Cart (link to my story) to carry several clumps to the back compost area.

Once cut down, it’s a good idea to put the stems in a back corner to allow any insects to complete their spring emergence. It’s always a good idea not to throw out the stems for recycling. We like to carry them to the back of the yard where they are placed on top of an open brush pile. This gives any insects that may be hibernating in the stems an opportunity to emerge from the grasses into a safe and favourable environment.

In addition, I like to take the softer grasses (most often from the dwarf fountain grasses) and place them near bird-feeding stations where the birds can take them to use for nest-building.

Modern hedge trimmers get the job done

The hedge trimmer we used was an older, high quality plug-in electric unit made by Bosch, but there are many units available that can tackle the job including newer, battery operated models that allow you to go anywhere in the garden without having to be tied to an electrical cord.

If you are looking to purchase a hedge trimmer, there are many issues to consider: electric vs. gas, blade type, blade length, blade gap, and much more. These feature become more or less important depending on how you plan to use it in the garden. If your main use is simply to cut down grasses, any of the better trimmers will get the job done.

For a full review of the best trimmers check out this article from Best Reviews. The Amazon products featured on this page are among the most favourable recommendations from Best Reviews.

We actually borrowed the hedge trimmer from my neighbour, who also uses it to cut down his ornamental grasses. The trimmer was originally purchased to cut back a massive hedge between our properties, but that hedge was removed last year and replaced with much nicer and wildlife-friends cedars.

Today, there is little use for the trimmer, so it has been given a new purpose primarily as an ornamental grass trimmer.

If you are a gardener on a budget looking for hedge trimmers, consider checking out thrift stores or Kijiji and other on-line buy- and sell-sites. The trimmers are fairly common sale items on these sites as a growing number of homeowners remove formal hedging and sell off their trimmers.

Since they are required only a few times a year and for a relatively short time, sharing a hedge trimmer with a neighbour is also a great way to cut costs.

If you are looking to purchase your own hedge trimmer, many of today’s models offer excellent ease-of-use whether you purchase and electric version or a battery-operated unit.

When to cut down ornamental grasses

There are generally three classifications of ornamental grasses: cool season, warm season, and evergreen grasses. The rules that govern the cutting, planting and dividing of these grasses vary slightly depending on the type. Proven Winners offers this explanation of the three types:

  • Cool-season grasses put on most of their growth in spring before temperatures begin exceeding 75 degrees Fahrenheit and in the fall when temperatures cool down. They generally maintain good colour through the summer but won’t grow much when it is hot. It is recommended to trim about 2/3 of the plant for cool-season grasses. Cool-season grasses tend to look good even as the weather cools. Leave their foliage in place until spring and then as soon as the snow is gone cut them back. Trimming cool-season grasses too harshly can irreparably harm the plant.These plants include:

    Calamagrostic acutiflora. Commonly called Karl Foerster Feather Reed grass. This 4- to 6-foot tall cool-season ornamental grows in zones 4-9 . Its flumes turn feathery as fall approaches making it a perfect addition for the late season and winter garden.

    Deschampsia. These cool-season grasses grow in most soil types in zones 4 through 9. D. cespitosa, or Blue Mohawk Soft Rush, forms a clump of thin dark green blades. The graceful plant gives way to numerous flower stems in summer with gold, silver and green tints. Northern Lights Tufted Hairgrass adds a colourful and natural look to any garden, with variegated leaves rising nearly 3 feet high. 

    Fescue, or Festuca. Blue fescue are cool-season grasses that grow as clumps of icy-blue leaves and can thrive in sun or light shade. They have deep roots that help them tolerate drought. The compact and cold-hardy perennial can add winter color to edgings or mass plantings.

    Helictotrichon. Also called Blue Oat Grass, H. sempervirens is a European clump grass that achieves its bluest color in drier soils.

  • Warm-season grasses won’t start growing until mid to late spring or even early summer. Their major growth and flowering happens when the weather is hot. They will usually turn shades of brown for the winter. These grasses include:

    Acorus. Also called Golden Variegated Sweet Flag, Acorus gramineous 'Ogon' has rich golden leaves that is semi-evergreen. It grows in zones 5 through 11 to a height of about 10 inches.

    Arundo (Arundo donax). Commonly called Giant Reed grass, Arundo is a warm-season ornamental that blooms in fall with purple stems. 

    Andropogon. This warm-season ornamental grass also is called Big Bluestem. I have grown it close to the street for several years and it performs magnificently each year despite the harsh conditions it faces. It grows in zones 4 through 9 and the thin grass blades can reach 4 to 6 feet high. The grass turns from blue-green to reddish in fall.

    Calamagrostis. Also called reed grass, C. brachytricha is a clump-forming warm-season grass that grows to nearly 4 feet high, displaying pinkish-tinted flumes in late summer or early fall. 

    Carex. More commonly called sedge, several pretty warm-season Carex grasses can work in a landscape. They rarely need to be cut back and are semi-evergreen in many areas.

    Chasmanthium. This native (Chasmanthium latifolium) has common names like oat grass or wild oats. It grows 2 to 4 feet high and is a warm-season, low-maintenance grass. It sends up blue-green leaves followed by graceful ivory seed heads.

    Hakonechloa. H. macra, also called  Hakone grass or Japanese forest grass, is a full-sun loving warm-season grass. ‘All Gold’ Japanese Forest grass has pure gold blades that cascade from the centre, reaching only about 14 inches high. Aureola Golden Variegated Japanese Forest Grass grows a little taller and adds stunning, cascading texture with its thick gold and green leaves. 

    Miscanthus. Usually called Maiden Grass, Miscanthus varieties have blue-green foliage that grows in a vase-like shape. Miscanthus Sinensis (pictured above) is a favourite of mine, especially in fall with its silver-colored seed heads late in the season.  

    Panicum. Switch grass (P. virgatum) grows well in zones 5 through 9. It can handle poor soil and drought and attracts birds to its flowering heads.

    Pennisetum. Commonly known as Fountain Grass, these grasses are actually from tropical areas. Probably the best known variety is Purple Fountain Grass, a colourful warm-season grass, that sports 2- to 4-foot high green and maroon glades all summer. Dwarf Fountain Grass can grow to 3 feet tall in a bright green mound with copper-colored seed heads in fall.  

    Schizachyrium. This tough and hardy grass, more commonly known as Little Bluestem is a native to North America and features narrow blue-green leaves.

  • Evergreen grasses are usually plants that look like grasses but aren't actually classified as grasses. Plants like the sedges and carex (see above) are grass-like but not grasses.

Vic MacBournie

Vic MacBournie is a former journalist and author/owner of Ferns & Feathers. He writes about his woodland wildlife garden that he has created over the past 25 years and shares his photography with readers.

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