Currant Events: Old Canes Need Regular Pruning

Q: I planted currant bushes last spring, and they have grown to 4 to 5 feet tall. How and when do I prune them?

A: There are two kinds of currants, black and red, and they are pruned differently. In either case, since you planted them just last spring, little pruning is needed now other than to remove weak shoots. Starting next fall or winter you should cut back to near ground level all or most canes on black currants over one year old, and keep only about six to 10 of the strongest new ones. Head these back, removing about a quarter of the growth.

Black currants fruit most heavily on one-year-old wood. This program should be carried out annually to ensure that no wood older than four years is retained.

Red and white currants fruit on short spurs made on older wood and at the base of new shoots that grow the preceding year. Try to maintain a red currant bush so it has four to six one-year-old canes, three to five two-year-old and two to four three-year-old canes. Remove canes at the base after their third or fourth year.

Any canes or stems older than four years tend to be much less fruitful than younger ones. You should also head back most shoots several inches each year.

Q: The bottom leaves on my dieffenbachia are turning yellow and drying up. Is it in trouble?

A: As dieffenbachias or dumbcanes age, like all plants, it's perfectly natural that the older leaves at the base of the stems die away. However if this is happening to more than a few leaves, it may be a nutrient problem (lack of nitrogen) or too little light getting to the lower leaves.

This plant needs as bright a location as you can give it in fall and winter. A south- or west-facing window would be appropriate, although spring and summer may require some shading. Any actively growing dumbcane should be fertilized every two to three weeks with a fertilizer containing nitrogen.

Late winter, spring, summer and early fall are the normal periods of active growth, though any plant receiving good supplemental artificial light may keep growing right through the winter and will likely need fertilizer applications then, too.

Q: I recently received some mole plant seeds from my brother in Indiana. He swears this plant keeps moles from his yard. How and when do I start them?

A: Send your mole seeds back to the Midwest. They may work against moles there, but there is absolutely no evidence that mole plants will keep Pacific Northwest moles at bay. In fact the mole plant, Euphorbia lathyris, once it is planted, may become a difficult weed to eradicate. So far trapping is the only proven method for dealing with our local moles.

Gardening runs Friday in Scene and Sunday in Home/Real Estate. It is prepared by George Pinyuh and Holly Kennell, Washington State University/King County Cooperative Extension agents, Mary Robson, Master Gardener program assistant, and volunteer Master Gardeners.