Thursday, December 27, 2007
Boxwood trimming can be done in early spring
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
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Q: I have some huge (4 feet in diameter) English Boxwoods around my house that have become overgrown. Some of them have even gotten bare where they have grown too close to their neighbors. Can I trim them and will they put out new growth? If I can trim, how severe can I trim? When should the trimming be done? This is in western Virginia.
A: Your overgrown English Boxwoods can be trimmed to encourage new growth. In Virginia, the best time to cut them back by several inches and stimulate them into making new outer growth to fill in bare area will be in early spring. Keep in mind that most new growth stimulated will emerge from buds close to the location of each trimming cut rather than all along the trunk from the cut down to the ground line.
If your boxwoods have been healthy, you can cut them down to half their present size at that time mentioned above. So, circle your 2008 calendar for mid to late March for this trimming. That is the time than Mother Nature prompts vegetative buds to open up and produce new shoots. Newly produced shoots should be able to survive at this time, also.
Boxwoods can also be pruned or trimmed lightly or even cut back heavily in April or later in the spring as well. However, the work should be completed before hot weather places stress on the plants.
It is alright to trim boxwoods lightly at this time of early winter if greens are need for winter decorations. The plants are dormant now. This work must be done before severe winter sets in.
Q: Would it hurt to leave a lot of fallen leaves that have blown into an azalea and rhododendron border that I have on the back side of my house?
A: Yes, autumn leaves that accumulate against the stems of azaleas and rhododendrons can cause those stems to crack or experience other winter bark injury as a result of moisture held by those leaves. Even though no one rakes the autumn leaves in the woods where wild azaleas grow, the damage potential in the landscape is great, especially in cases where the azaleas have been under stressful conditions like our recent severe drought.
Q: What is the proper procedure for getting my container-planted rose bushes through the winter here in Roanoke? They sit on my deck. Should they be brought inside for the rest of this winter?
A: If you have not already done so, do the fall jobs for container roses, which are the important chores for rose sanitation. Remove all dead, diseased, and damaged parts as would be done for roses growing in a traditional rose garden or landscape. It might be hard to determine which twigs or branches are dead now that we’ve had cold weather, so look for cracked or abnormally colored parts as indicators of dead wood.
Next, provide winter protection for dormant rose plants in your containers to protect the above ground rose graft areas and lower cane buds. Carefully, apply a mound of loose soil or mulch over the bottom 10 inches of your container rose canes to provide insulation against cold air for the rose graft unions and lower buds.
Then, prune back only the tip portions of long rosebush canes to prevent winter winds from shaking the plants and possibly loosening the roots in the containers.
Another outside container job will be to wrap rose containers with several layers of burlap or other nonplastic material to insulate the pots or boxes, thereby preventing root death as a result of cold temperature penetration into the container soil.
In this area, the winters should not be frigid enough to penetrate very far through container walls, which would necessitate bringing those roses inside to a cool but frost-free spot inside. If your containers are very thin, your roses have been in the same containers for many years, and you do decide to bring the pots inside, your goal will be to keep the plants dormant. Thus, the storage place must be cooler than 45 degrees F.
Q: Even though the temperatures have been chilly, I noticed that some of our spring bulbs are showing sprouts of foliage coming out of the ground. Should I put mulch over that ground to slow down the growth of these bulbs before their time? I live here in western Virginia but not in the mountains.
A: Additional mulch will prevent the warmth from winter sun reaching the soil below. However, I would not rush out to get mulch over the premature shoots. Mother Nature should handle this situation anyway. Plus, I do not recall ever seeing research suggesting how much mulch is needed to insulate soil for so many degrees. There is the risk that soil below excessive mulch does prevent soil “breathing” below.
