Is Cutting Back Ornamental Grasses Really Necessary?

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This Miscanthus sure looks like it needs pruning.

One garden task almost universally recommended for the end of winter or early spring is to cut back ornamental grasses close to the ground. However, as a laidback gardener, I object to this generalization. Isn’t there any way of avoiding this task? Let’s look and see.

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Evergreen grasses, such as this blue oat grass (Helictotrichon sempervirens), don’t need pruning.

First, some grasses are evergreen: blue fescue (Festuca glauca and others), blue oat grass (Helictotrichon sempervirens) and most sedges (Carex), among others. Since they are evergreen, they don’t normally need pruning. Perfectionists can always  pull out any dead leaves one by one (wear rubber gloves: the dead leaves will be easier to hold on to) in order to “clean” the plant, but otherwise they will look pretty good on their own with no special care at all. Of course, sometimes after an unusually harsh winter, the foliage of even evergreen grasses can be severely damaged. If so, do cut them back to about 3 inches (7.5 cm) from the ground. This is for emergencies only, though. They don’t appreciate harsh pruning and this could weaken or even kill them if you repeat it annually.

Deciduous Grasses

The majority of commonly grown ornamental grasses, however, are deciduous; their foliage dies and turns brown in the fall, but remains standing. Moreover, their winter effect, with arching leaves and feathery plumes still standing proudly erect, is one of their main attractions. But by the spring, the leaves are starting to collapse and the beautiful flower spikes have begun to crumble. It would seem that pruning is an absolute necessity!

But not so fast!

In nature, nobody prunes deciduous grasses. New leaves simply emerge through old, tired ones and eventually cover them up. And the old leaves eventually decompose and disappear, usually the same year. Allowing the old foliage to remain intact will slightly slow down the grasses’ spring growth, but otherwise doesn’t harm them… and an unpruned plant will soon catch up to a pruned one. If your ornamental grass is in the back of the garden, where the transition period where you see a mixture of green and brown leaves (which can last up to mid-July) is not so visible, you can simply walk away and let the plant take care of itself.

In spots where the grass is highly visible, however, you may want to cut the grass back in early spring. But there are still a few tips to help make the task less arduous.

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Pruning is easier if you tie the stems and leaves together.

First, before cutting back, use a piece of cord to attach the stalks together, pulling them tight to form a sheaf. You may prefer to attach taller grasses in two or more places, giving a column effect. This way, you won’t have grass leaves in your line of vision as you prune and they’ll all be nicely attached in one single package, making for easier removal once you’ve cut them down.

20150416EAll you have to do, then, is to cut the sheaf off about 4 to 6 inches (10 to 15 cm) from the ground. You can do this with pruning shears, of course, but then you’ll have to spend a lot of time bending or kneeling, a difficult position for older gardeners to maintain. Also, you’ll soon discover many grasses have sharp leaf edges, not something you want to stick your hand into. Instead of pruning shears, try cutting your grasses back with a small chainsaw (the fastest method) or string trimmer (slower but still effective). This takes little time and you can often do it while remaining standing. Afterwards, run the sheaf trough a shredder: it will make make great mulch!

20150415FBut there is an even lazier way to prune deciduous grasses: set them on fire! In nature, tallgrass prairies the natural habitat of most of our ornamental grasses burn every 1 to 5 years. The fire is therefore part of their natural lifecycle. Indeed, without fire, there would be no prairie: trees and shrubs would take over and the land would become a forest. Fire cleans out dead stems and leaves, kills invading plants (notably tree and shrub seedlings) and fertilizes the soil. And grasses themselves are not adversely affected by fire: in fact, they have evolved to tolerate fire and even enjoy this “natural pruning”. A burnt grass will grow much better than a grass that is cut back. Try it and see!

Of course, in this day and age, it is no longer possible to burn grasses in most urban areas. Check with your municipality to find out what the restrictions are. If you do have the right to do so, any burning must be done in early spring, when the ground is still soaked. Furthermore, for security reasons, wait for a windless day and, before starting the burn, water all nearby non-grass plantings, soaking their leaves and stems. And stay nearby, hose in hand, to extinguish any stray spark.

To anyone who might complain that burning can’t possibly be environmentally friendly, think again. This is the most natural and environmentally friendly method of all, part of Mother Nature’s plan. How can you go wrong when you do what Mother Nature intends?

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