Running out of time to prune spring bloomers

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By Jeneen Wiche

Do you have any unruly spring flowering shrubs? Well, now is your opportunity to get them cleaned up, in fact we are about to run out of time if we want to hold on to next years buds.

There are a couple of plants that invariably grow out of control and they all seem to be spring bloomers. Lilacs, viburnums and azaleas top the list when it comes to the question when is the best time to prune? These are the shrubs that most often get neglected and therefore become monstrous in size and leggy in form. We had such a beautiful spring with cool temperatures and ample rainfall that most plants put on more then normal growth. Alas, the monstrous and unruly are even more so in 2008.

There is a rule of thumb that gardeners live by when it comes to pruning blooming shrubs: if it blooms before June 1st it blooms on buds set last year; if it blooms after June 1 it blooms on new growth this season.

So, if you are a spring flowering shrub that means you should be pruned and just after bloom is finished or as soon as possible there after. We are running out of time (which is not to say you cannot do it, rather just that you will loose some of your bloom for next spring if you prune too late in the season). Most spring flowering shrubs will have set all their buds for next year by this July.

There will be an advantage to pruning a little late this year (but not too late) if you experienced a 17-year cicada emergence. If you prune now you will also prune out egg-laying damage (and if your timing is really good you may also prune out the actual eggs that were laid in twigs which remain for a couple of weeks in the twig) which is evidenced by a long slit on the underside of pencil-sized twigs.

When pruning set a goal for yourself that includes reducing size, thinning, and removing the oldest, dead or pest damaged wood. Another rule of thumb is that we should only remove about one-third of a shrub at a time. All this pruning will encourage new, vigorous growth and will improve the overall appearance and health of an old shrub.

Summer blooming shrubs like spirea and weigelia can still be pruned, as well, although it is best to get this done in early spring. Pruning now will delay your summer bloom a little but the act of pruning will encourage new growth and bloom. Cicada issues may play a role in some delayed pruning for summer bloomers this year, as well.

Evergreens like boxwood, taxus and holly are best pruned after the threat of frost has passed in spring but, again, you can still tackle the chore now to reduce size and thin the shrubs. These evergreens will put out new growth after pruning just not as vigorously as they would if you had done it earlier in the spring. Your next best opportunity is to do thin and prune again in late summer, early enough for the new growth (that is always stimulated after making a pruning cut) to harden off before our first frost.

A thorough investigation of your yard will be a good idea this year if you have cicadas and some selective pruning of shrubs and trees may be necessary to clean up some flagging of small branch tips where egg-laying has occurred. Get in pruning shape by addressing some of your other spring and summer blooming shrubs that are out of control now, before your window of opportunity has closed.