Pruning Shrubs

ChiloquinNews article 4/4/2011

By far the best time to prune a shrub is right now, when you can actually see what you are going to cut. Once the shrub is covered with leaves, you just can’t see what you need to do. It’s a bit daunting though, looking at a tangled mass of stems and wondering where on earth to begin, but it gets a bit easier if you break it down into several steps. Whatever you do, don’t shear the poor plant into a round ball or a rectangle. Shrubs have wonderful natural shape and it’s worth the time and effort to enhance the natural shape rather than turning it into a geometric eyesore.

You probably won’t need to do a comprehensive pruning like this every year. Most years you can just go to step 2 and then stop. If you have a small, new shrub then definitely stop at step 1, and allow it a couple of years to get some growth on before you go cutting it back. You could cut out the dead wood but wait until there are absolutely no more freezes to come.

 Caution though – not that you are likely to be out pruning when it’s below freezing, but if you do think about it, then don’t. Cutting frozen wood causes it to burst at the cut, and sends cracks down the stem that never properly heal.

 Step 1: If your shrub is grafted onto a rootstock and there are suckers present (mostly roses), you must remove them or they will take over. The best way is to dig down to the root and tear the sucker off. You can just cut them off (as I usually end up doing) but then you will get more and more shoots from the cut stem every year.

Step 2: Cut out all the dead stems. The dead stems will look grey or blackened and when you cut them there will be no greenish colored tissue, and they will also be quite brittle. Cut the dead stems completely out at ground level, and partially dead stems, cut back an inch or so into the live wood.

The pruning cuts should be made at a 450 angle, just above an outward facing bud. The 450 angle allows the cut to shed water, and the outward facing bud will grow out away from the shrub, rather than inwards towards the center where it will tangle with other stems. And cut just above the bud, because all of piece of stem that you leave above the bud will die back and is unsightly as well as a possible source of disease.

Step 3: Now cut out all the branches that are rubbing on other branches or growing towards the center of the shrub. Choose the thinnest stems to cut back, and cut them right back to the ground, or to the main branch that they are growing from. You want to remove these because if the center of the shrub is too crowded with stems there will not be good air circulation, and those rubbing on each other can cause injury to themselves. Both of these conditions are good for promoting disease, which is not something that you want. Any stems emerging from the ground that are thinner than a pencil should also go. By now your shrub should be looking a good deal neater!

 Step 4: Is the last step where the difference comes in between shrubs that flower on new wood and those that flower on old wood. If your shrub flowers on new wood then remove last year’s flowering tips, and head back any vigorous vertical shoots, by no more than 1/3 the length of the stem. If your shrub flowers on old wood, then wait to do this until after it has flowered.

 Some plants that flower on new wood are Potentilla (cinquefoil), Holodiscus (ocean-spray), Lonicera (honeysuckle), Sambucus (elderberry), Rosa (repeat-flowering shrub roses that flower some on old but mostly on new wood).

 Some plants that flower on old wood are Rosa (once-blooming shrub roses), Akebia vine, Amelanchia (service berry), Chaenomeles (flowering quince), Syringa (lilac).


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