Q. Two years ago I planted English Ivy in a shady area where I had a difficult time growing grass. It has grown exceptionally well, even to the point of growing up onto the trunks of my trees. Is there any problem with allowing the ivy to grow up into the trees?
A. I am not aware of any research suggesting that ivy itself will damage the trunks of trees. However, ivy rarely stops at the tree trunk. Eventually it ends up in the crown of the tree and begins to grow over branches and leaves. This can kill leaves and branches. The other problem is that the longer the ivy stays on the tree, the more tenaciously it clings to it. If you wait too long to pull it off, you may pull off some tree bark along with the ivy. This is damaging to the tree and should be avoided. If you are going to keep the ivy, I would suggest that you keep it clipped off the trunks of your trees.
Q. I love my roses, but I have lost my desire to do the repeated sprayings required to maintain them. Why are so many sprayings required to maintain roses?
A. Roses need the repeated sprays for several reasons. First, most roses are vulnerable to an exceptionally long list of insect and disease pests that begin attacking early in the growing season and continue until late in the season. The second reason is that some of these pests reproduce repeatedly from spring until fall. For example, the fungus that causes black spot disease produces new spores all summer. So, unless your spraying kills every bit of the fungus, it will come back, and a succession of sprayings is required to control it.
The good news is that no two roses are alike, nor are they created equal. This is not only true of their flowers, but also of their resistance to disease. Some rose species and cultivars have significant genetic resistance to insects and disease. If you select these roses for planting, you can greatly reduce or even eliminate your need for spraying.
Check out the Berkeley Horticultural Nursery Web site for specific roses to consider: http: / / www.berkeleyhort.com / roses / rdiseaseresistant.html.
THIS WEEK'S CHECKLIST
1. Short summer downpours may provide some help to your flower beds, but watch flowerpots that have trays underneath them. Trays full of water can cause root rot. They should be emptied after heavy rains.
2. This is a good time to prune evergreens such as yew and boxwood. These plants have completed most of their yearly growth; pruning now may suffice for the entire year.
Dennis Bishop is an urban horticulture educator with the Maryland Cooperative Extension Services. If you have a gardening or pest problem, you can call the Home and Garden Information Center hot line (Monday through Friday, 8 a.m.-1 p.m.) at 800-342-2507. You can also e-mail questions, order publications and diagnose plant problems by visiting the Web site, www.agnr.umd.edu / users / hgic.