Bug oil: Spray shrubs and other plants with dormant oil to suffocate overwintering insects and their eggs. Choose a time before leaf buds start to open, when daytime temperatures are expected to remain above freezing for two to three days. Plants that often require dormant oil application include hawthorn, crab apple, honey locust, dogwood, purple-leaf winter creeper ground cover and Norway and silver maple trees. Dormant oils especially are effective in controlling scale insects and many types of mites.
Source: Illinois Landscape Contractors Association.
BEST NEW DESIGN BOOK
Man with a plan: Tim Newbury, a veteran British landscape designer, shows how to apply principles of garden design to yards of various shapes, sizes and functions in “Garden Design Made Easy” (Ward Lock/Sterling, $35).
Q. Please advise on grapevine pruning. My vines are overgrown and need help.
–Palos Hills
A. Right now is an ideal time to completely rejuvenate an out-of-control grapevine. Remove it from whatever support it is on. First thin out the vine so you have one major supporting trunk. Then move up about 3 feet from the base and select four to six lateral canes to train. Avoid choosing the largest canes, because they will not be good fruit producers. Prune the chosen canes back so that 10 to 15 buds remain on each one and then reattach the canes to a horizontal support. For more detailed and illustrated information on pruning grapevines, contact The Chicago Botanic Garden’s Plant Information line (847-835-0972) and request Plant Fact booklet 36 ($2.44).
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Lee Randhava writes for the Chicago Botanic Garden. Send your gardening concerns to Questions, Plant Information, Chicago Botanic Garden, 1000 Lake Cook Rd., Glencoe, IL 60022. Letters cannot be answered individually, but those of general interest will be answered in this space.
