Thursday, July 17, 2008
Making vines grow their best
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 a clematis vine at my lamppost that blooms beautifully in the spring and early summer. Then it's only green leaves. I've heard that black eyed Susan vines will bloom all through the summer and into the fall. Can I plant the Black eyed Susan with my clematis, cut back the clematis after it stops blooming, and then have the black-eyed Susan finish the season? Or is there another vine that you would recommend?
A: Cutting back your clematis after it finishes blooming is the part of your plan that could be harmful. All the leaves produced by the clematis during the whole summer conduct photosynthesis through which they produce food for the vine and storage for future growth and survival.
Black eyed Susan vine is a colorful companion to grow along with the clematis. I have read both praises for Black eyed Susan vine and negative comments, so I understand that it can behave differently in various climates. This vine might work well for you, so I’d recommend trying it. However, Black eyed Susan vine could be too vigorous and shade out your clematis foliage or it might attract insect pests to the lamppost garden.
Other annual vines that you could try growing along with your clematis include moonflower vine (botanic name Ipomoea alba), cardinal climber (botanic name Ipomoea X multifida), morning glory vine (Ipomoea nil, I. purpurea, I. tricolor), cypress vine (Ipomoea quamoclit), sweet pea (Lathyrus odoratus), or nasturtium, if trained (botanic name Tropaeolum majus).
I make no guarantees with any of these vines nor that the response you get will be what you want. Growth of these other vines can vary because of your microclimate, amount of sun and water, and your soil.
Q: I have had a wisteria bush in my yard for about five years and it has never flowered. Is there a certain way to prune it that will force the flowers, or is it a matter of reaching the proper age for blooming?
A: Wisterias can take many years before they will produce flowers if they were propagated from cuttings taken from non-flowering wisterias. Patience will be needed. There are things that you can do, though.
Abundant nutrients in wisteria soil hinders their flowering. Nitrogen, especially, promotes excess vegetative growth of vines and leaves at the expense of early spring wisteria flowers. If your 5-year-old wisteria bush receives nitrogen from adjacent lawn fertilization, create a 10-foot ring of no-nitrogen application around the wisteria. The phosphorus fertilizer sold as “superphosphate” can be applied to the wisteria area in mid-fall to enhance wisteria blooms.
Pruning will not guarantee blooming, but “root pruning” a non-blooming wisteria has been suggested by Dr. Michael Dirr in his book, "Manual of Woody Landscape Plants," as a good way to stimulate flowering. To do this, insert a round pointed shovel 8 to 10 inches nto the dampened soil 18 to 24 inches out from your wisteria trunk in mid-fall to sever some wisteria roots.
Dirr also suggested cutting back vigorous growth, leaving only 3 to 4 buds. Buds are little growths along the vine that are like “eyes” on an potato. Woody plants in the temperate weather zone have a bud at the base of each leaf.
Remember that wisterias have compound leaves made up of many subcomponent leaflets growing from a central leaf stalk. The whole group of leaflets is 1 leaf. I’d suggest cutting those vigorous shoots in mid- to late spring.
