Should ornamental grasses be cut back?

If so, when and how much? What time of year can ornamental grasses be divided?

By all means, leave your ornamental grasses standing until spring. They add such wonderful interest to your garden in winter. When you begin to see new growth next spring, cut back the grasses to about 10 cm (4 in.).

Here are some tips for dividing your ornamental grasses next spring:

  • Do not allow the exposed roots to dry out. Try to do this on an overcast day. Cover any exposed roots to protect them. Smaller grasses can sometimes be pulled apart. Larger clumps can be dealt with by prying apart, using two garden forks jammed straight down into the centre of the grass clump.
  • The forks should be back to back. Then pry them apart at the tops of the handles. A sharp shovel can penetrate the centres of some grasses. For large clumps of grasses such as Miscanthus cut the foliage back first to about 10 cm (4 in.).
  • Use a wide-blade axe to hack the clumps into smaller clumps. Pry out. Further divide to the desired size with pruners. Trim away any dead roots. Replant and water throroughly.
  • Another technique for large ornamental grasses: Dig a trench around the grass clump. Pry out the entire root ball with a shovel or crowbar. Cut into pieces using a hand saw. Replant and water thoroughly.

(Source: Ask a Master Gardener, Answers to your Gardening Questions from the Master Gardeners of Ontario Inc., pp. 14-15. Photo credit: Amy Urquhart)

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