GUELPH-WELLINGTON
MASTER GARDENERS

 


SHRUBS


Pruning Korean Lilac


I am not sure how to trim Korean Lilac bush. It is really growing but I need to try and shape it or trim it back. Is there a good time to try and trim it back? It is currently still in bloom. 


Answer: Lilacs should be pruned immediately after bloom. In fact, most sources advise that you cut off the dead flower clusters, but that is not always practical depending on the height. 


Use good basic pruning principles:

  • Remove an dead, diseased or damaged branches.
  • Remove any branches that grow toward the centre of the tree, or that cross other branches.
  • Remove weak, spindly growth.
  • "Head back" the longer branches to the size you want. Make a slanted cut where the lowest point is about 5 cm (1/4 in) beyond an outward-facing bud or leaf.
  • While pruning, remember the shrub needs good air circulation in the centre in order to avoid fungal problems like powdery mildew. 
Here is a link to further information: http://gardenersnet.com/lilac/lilac02.htm

Rose of Sharon (Hibiscus syriacus)

I have a Rose of Sharon that has been planted for about two years now. Last year it was beautiful. This year the leaves were very slow in coming but appear to be mostly out now. However, in the centre, I have quite a few branches that have no leaf growth whatsoever. Should I cut these branches off to just above the last sign of leaf growth? Or what do you suggest? Someone told me that if you bend the branches and the break, they are dead but if they bend, they are still alive. Is this a true test?

Answer: The ideal time to prune Rose of Sharon is late winter or early spring. However, dead or damaged stems should be pruned out. Rose of Sharon shrubs are notorious for being late to bud out. If your shrub is now leafed out but there are bare dead stems, you should prune them down to an outward-facing leaf. If the whole branch is bare, go ahead and cut it back to the source bran. The "bend test" may work sometimes, but you might also damage a live stem that way.











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