Some folks in this valley are still advocating hard pruning of roses before winter arrives, and they should not advise that.

Pruning rose canes opens wounds that bacteria such as the Pseudomonas syringae variant may enter, killing your rose bush.

The disease these bacteria cause is popularly known as “bacterial cane blight,” and it has been in this valley and elsewhere for several years now, but few scientists had written about it until Dr. S. Krishna Mohan, plant pathologist at the University of Idaho research station at Parma wrote a paper on the topic.

Even pulling leaves off the canes results in scars the bacteria may enter. In spring the disease appears similar to winter kill of canes, but scratching the cane with a thumbnail reveals a difference — if it’s dry and black under the bark of the cane, it’s winterkill. If it’s wet and red or brown in color, it may be the bacterial disease.

Another reason you should not severely prune roses in autumn is that a hard freeze may kill part of the cane, and if you’ve already pruned it back, the freeze may kill the cane farther than you’d like. Actually that’s why we shouldn’t do any extreme pruning in autumn.

Long canes that can be windblown and harm other canes as they’re whipped by wind should be removed or at least cut back.

Our winters have not been terribly severe for several years, although we have had sudden steep drops in temperature. If roses have been allowed to make hips, preparing for winter dormancy, they should be all right. Some folks still protect rose shrubs with a mulch of soil or at least leaves several inches deep over the crown. Others find it unnecessary.

If you’ve given your needled and scale-leaved evergreen trees and shrubs a good long drink before winter strikes, they should survive. Some folks want extra insurance, with an anti-transpirant coat such as Wilt-Pruf.

Wilt-Pruf label instructions include that, when spraying on arborvitae, cypress, cedar or juniper, be sure to wait until moisture has retreated to the root zone or else moisture in the foliage could freeze and burst, damaging the tree or shrub. These species tend to be those that turn bronze in winter, so I’ve asked several arborists if that bronze color means moisture has retreated to the root zone.

The answer, invariably, was “I don’t know.” I asked the folks at Wilt-Pruf, and they said they didn’t know how to tell whether the moisture had retreated to the root zone, but they just waited until there had been some cold weather, then above-freezing daytime conditions were right to use the spray. They’re located in Connecticut, and they use the product on their shrubs and trees around U.S. Thanksgiving time.

I still don’t know why some of those trees and shrubs turn bronze (Mahonia leaves turn maroon), but now my guess is that it’s in response to the lower light level and/or reduced daylight hours, the evergreen version of deciduous leaf dropping.

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It’s about time to cut down our “Plume Poppies,” those 8-foot giants with two-tone leaves. The upper part of each huge leaf is grey-green, the back of the leaves velvety white. Even a light breeze is enough to initiate a leaf-flashing show even more enchanting than the flickering leaves of aspen.

Plume poppies are known botanically as Macleaya cordata, and they have branched flower stems of clusters of white stamens that appear flowerlike from a distance.

Send garden questions to melauter@earthlink.net or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.