Ask the gardening expert

Celeste, I’ve missed your columns because of being gone. Have you mentioned about not pruning during severe weather conditions? Maybe it’s too late after this long cold spell and you may have already covered that subject

Yes, I think I probably did, but then, after so many years at this, I cannot remember when or even if I talked about it.

Pruning trees in winter is a chore I haven’t gotten myself into. Being a “fair weather” gardener, there are some serious gaps in my horticultural experience, and knowledge, so I say thank goodness for the Internet; that is a lifesaver for so many reasons.

On this question I am happy that I can rely on a trusted scientist’s writings. The fact that this person is with OSU Extension Service working in the Pacific Northwest gives me confidence. So I’m offering Lynn E. Long’s paper on our subject. Even though she has addressed this paper to the industry, I feel it is general enough to be useful to the homeowner:

Lynn E. Long, Extension Horticulturist:

When a pruning cut is made, there is an invigoration of the tissue around that cut making the limb somewhat more cold sensitive than non-pruned limbs. The greater the percentage of wood removed, the greater the stimulation to the tree. Therefore, big cuts and cuts on young trees are potentially the most hazardous cuts. In addition, special care should be taken to avoid pruning old, weak trees immediately before or during intense cold. Cold sensitivity seems to last for a period of about 10 days. As time passes after the cut was made, the tree becomes less and less sensitive until it regains its former cold hardiness level, approximately 10 days after pruning.

Summer pruning a portion of your orchard each year can remove some of the pressure to finish before bloom. Planning your winter pruning is also important. Since young trees are more sensitive than large trees, plan to prune your healthiest mature blocks at the time of year when cold spells are most likely to occur.

Highlights: Pruning causes a brief period of decreased winter hardiness. Large cuts and cuts on young trees are potentially the most hazardous.

I have a beautiful old weeping crabapple tree. I just recently noticed that it has a 3-inch-wide crack in the trunk and the crack is filled with dead wood. Is there anything I can do to save this tree? It is beautiful in the spring, but the leaves shrivel and turn black then new leaves grow back and by summer it looks OK, but not great.

I took a look at WSU site “Hortsense,” but didn’t pinpoint the problem, since I’ve not seen the tree. Maybe it would be good if you read the WSU site yourself: pep.wsu.edu/hortsense/ (go to fruit trees, then common disease).

It really does not sound like the split is related to the leaf problem.

The split in the trunk is probably not going to heal, and you needn’t do anything to aid it as you could be causing more harm than good. The leaf problem sounds like a serious case of apple scab. If this were me, I’d find a replacement now, look for a disease-resistant variety. The young ones usually bloom early and may be doing a good job of blooming this coming spring. Horticultural science has learned so much, and are constantly working on developing new strains that escape disease, or mostly so.

I’m upset and annoyed. Last week I bought a poinsettia at a large store and it was so beautiful. I got home and found that it had died even before I could get it in the house. I asked the store to reimburse me and they did, but said it was not their fault. I kept it in my car too long, they said. How could that be? I made only one more stop, then home. I felt that was a short time, and wonder if others have had the same trouble?

Tell you what — it was not all the store’s fault. But they should be warning their customers when buying tropical plants, and especially poinsettias, that they cannot take cold, certainly not ride around in your car as you finish running errands. They die quickly in cold temperatures. I wish garden center folks would warn buyers, or even supply a cover of some sort to help folks get them into their cars and home safely. I have successfully gotten indoor plants home in icy weather with a large paper bag over the top of the poinsettia to increase its chances of getting into the house, and then removing the cover only in the warm house. These plants cannot take cold; they are tropical! Tropicals cannot take temps in the 20s.

Celeste Lindsay is a WSU-certified master gardener. Send questions to mslindsay8@gmail.com.