Caring for Ornamental Grasses – When to Trim and How to Divide Them

2 min read

Caring for Ornamental Grasses – When to Trim and How to Divide Them

Ornamental grasses add height, movement, texture and colour to any landscape. They are tolerant of many soil types and thrive with lots of sun, little rain and no chemicals or fertilizer. Native grasses, especially, are also an attractive food source for birds and butterflies.

 

Types of Ornamental Grasses

There are three types of ornamental grasses: cool-season, warm-season or evergreen.

Cool-season grasses grow the most in spring, before temperatures rise above 20C, and again in the fall when temps get cool again. They generally maintain good colour through the summer, but won’t grow too much when it’s hot.

Warm-season grasses won't start growing until mid to late spring or early summer. Their major growth and flowering happens when the weather is hot, and they turn brown for the winter.

Evergreen grasses are usually plants that look like grasses but actually aren’t. Plants like sedges and carex are grass-like, but not grasses.

 

When and How to Cut back

Warm-Season Grasses: Cut back in the fall or by mid- to late spring.

Once your warm-season grasses turn brown in the fall, you can trim them back at any time. If you do a fall cleanup in your garden, you can trim them so they’re only a few inches tall. Or you can leave them for winter interest and trim by late spring before new growth begins.

Cool-Season Grasses: Cut back in very early spring.

Leave the foliage in place through the winter until the snow melts, and then trim them back, leaving 1/3 of the plant. Cutting back too hard is not good for cool-season grasses.

 

How to cut back grasses

Gloves are highly recommended as some grasses have sharp edges.

For smaller grasses, pruning shears are adequate for trimming back.

For larger, more established clumps, you may need a weed eater or hedge trimmers. Pruning shears will still work, it’s just more labour intensive.

Tip: Tie grasses into a bundle prior to trimming to for easier cleanup.

 

How to Divide Ornamental Grasses

Dividing ornamental grasses is very similar to dividing perennials. Keep in mind to divide any ornamental grasses when they are actively growing, but not flowering.

Warm-season grasses – divide anytime in spring through mid-summer.

Cool-season grasses - divide in spring or early fall.

Evergreen grasses  - divide in spring only. Evergreen grasses don’t ever go dormant, so ensure that when any division happens, they will have enough time to recover.

  1. Dig up the grass clump.

  2. Using your hand, a knife or shears, cut or pull the clump into several pieces. Ensure each piece has some roots.

  3. Replant as soon as possible.

  4. Trim off dead material and water thoroughly until well-rooted.

 

Sit back and enjoy the grasses waving in the breeze.



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