Perennial Grass Care

A couple weeks ago on Gardenista, I spoke about winter garden work – mostly, perennial grass care. Read below on a how to care for some of my favorite perennial grasses, including some unique techniques to keeping them looking fabulous.

During winter, I leave my perennial grasses standing tall for as long as possible so the birds can get to the little seed pods. But with the season coming to a close, I’ve finished pruning the other perennials—roses, lavender, and mint—and it’s time to get the grasses ready for their spring growth.

Different grasses have different needs. Some should be pruned. Others need to be left alone. And then there’s a third type of perennial grass that falls in between—and benefits from a simple technique I have developed of brushing the blades. I find that after being brushed, these grasses don’t need to be pruned any time of year. (After they are cleaned up, the fresh growth fills in quickly.)

The first thing to do is to identify your particular grass’s needs. (Nothing is worse than when you see a grass pruned totally hacked to the ground without cause. Then it takes almost a full growing season for it to fully bounce back.)

Below is a list of grasses I plant the most—and a description of how to care for each. (Of course there are many, many more grasses, but if you start with some of these grasses, you’ll get the hang of how to care for different varieties.) As always, experiment—and feel free to ask questions in the comment section.

Grasses to Brush

  • Carex buchananii
  • Stipa ichu
  • Festuca glauca

Above: To brush, simply take hold of a bunch of grass as you would long hair. Bundle in a section and brush toward the top.

Above: Use any old type of brush, even your worn-out hair brushes. There may be dead blades of grass clustered on the outer edge of the plant, simply pull those out by hand. Dead grass blades should come out easily and in complete sections if it is full dead. It shouldn’t take more then a gentle tug. Finger through to clean all the loose blades.

Grasses to Prune

  • Miscanthus (all)
  • Pennisetum (all)
  • Chasmanthium latifolium
  • Hakonechloa macra ‘Aureola’

I find that a good rule of thumb for pruning grasses is to cut about 4 inches from the ground. You can go lower during a year when the grasses are growing extra full, but not much more than from 2 to 3 inches to be safe. The goal is to remove excess dead foliage, but we don’t want to tax the plant to the point of weak growth. Before pruning, be sure your plant is healthy with the right amount of water, a tiny bit of organic fertilizer, and space to grow.

Grasses to Brush and Prune

  • Panicum_ spp.
  • Spartina pectinata
  • Isolepis cernua

With Miscanthus (the first pic in this post) grasses, I prune every other or every two years, not yearly. The years I don’t prune, I use the brushing technique.

Grasses to Leave Alone

Some grasses don’t need any pruning what so ever. Thin out the dead blades from time to time. But generally speaking, I don’t touch these two grasses at all. However, I do tend to divide Phormium every four to five years. I used to prune down every time I divided a clump, but I found it didn’t stimulate root growth very much at all. In fact, it seemed to slow the establishment of the new divisions. So now, I never prune Phormium.

  • Phormium
  • Liriope spicata
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