Fall Garden Maintenance: Pruning and Dividing Ornamental Grasses & Perennials

Maiden Grass 'Yaku Jima'

Ornamental grasses can add much interest to the winter landscape and can be enjoyed all winter long.  Here's a helpful fall tip for pruning and dividing your ornamental grasses such as 'Miscanthus sinensis' Maiden Grass or Dwarf Fountain Grass 'Hameln'. Winter cold can do harm to the root system of grasses.  It is best to cut your grasses back in late March to early April in order to protect the roots and ensure the health of your plants.  If your ornamental grasses become a bit unruly by the end of the fall cut them back to only one half the height of the plant and leave the rest for early spring. Another trick is to wrap a bungee cord about halfway up around the center and let the grasses drape over keeping them upright and in place. In late March or early April cut your ornamental grasses to approximately 4-6 inches above the ground so that new growth can emerge. 


Sedum & Fountain Grass 'Hameln'

Since new growth occurs on the outside edges of the root crown, the center of ornamental grasses often start to die out as the grass matures.   If your grasses are starting to hollow in the center before winter it may be time to divide them. Fall is the best time for this procedure.  If you should decide to divide your larger grasses an axe or hacksaw may come in handy.  Use a sharp spade to completely dig around the perimeter of the grass and lift up out of the ground.   This may take some muscle and may require a couple of extra hands!  Now depending on the size of the grass you can use either an axe, hand saw or a gas powered saw to divide it into cleanly cut pieces for planting.  Dig a large enough hole to allow the roots to spread and plant the new clumps of grass at exactly the same height as they were planted before. Remove any loose pieces, add mulch for protection from cold and water in thoroughly. 



Stella D Oro Daylily

When your daylilies are at the end of their bloom in August and the foliage is starting to yellow cut them back half way to the ground. They will rejuvenate giving you lush green foliage and even more blooms throughout September and into October. (Works best with Stella D Oro Daylily).  Dividing daylilies is also best in the fall for the health of your plants.  Simply dig deeply around the perimeter of the plant and gently lift the entire clump out of the ground.  Use a sharp spade to divide the plant into parts and plant each section into a hole twice the size of the root ball.  Be sure to get at least three or more strong shoots and a good root ball around the plant.  Cut the foliage back halfway and back fill with soil around the plant.  Then add mulch around the base to protect the roots and water thoroughly.   Keep the plant well watered until the roots become established.  At the end of the season once the fronds have turned completely brown remove all foliage to the ground to prevent fungal disease over the winter.  Other plants that benefit from fall division are salvia, iris, peony, hosta, goldenrod, monardia (beebalm), nepeta, coreopsis and sedum. 

Nepeta 'mussinii'

It is also good practice to prune back spent perennials to within a few inches above the ground in the fall and to surround the area with a layer of mulch.  This procedure prevents possible infection from fungal disease and helps to insulate the plants during winter. Perennials that benefit most from fall pruning  include hosta, daylily, nepeta, salvia, coreopsis, gaillardia, phlox, monardia, veronica, platycodon and yarrow. Liriope can be pruned in fall or late winter before new growth emerges.  Heuchera (coral bells), astilbe, liatris, lavender, perovskia (russian sage) and lupine are all cold sensitive and should be left to be pruned in early spring.

Author: Lee@A Guide To Northeastern Gardening Copyright 2010. All Rights Reserved.