Relocated gardeners from warmer climates may find Northern Nevada winters a little daunting.
Linda, a recent arrival from Vallejo, Calif., recently asked me what to do about perennials at this time of year. Particularly, she wanted to know if she should cut back mums, bluebeard, spiraea and coreopsis.
There are varying schools of thought on fall and winter care of perennials. Leaving the stems on through the winter captures drifting leaves and mulch, which protects the root ball, holds soil moisture, and reduces freezing and thawing problems. So I leave most of my perennials alone until spring, because the trapped leaves and occasional snow maintains soil moisture in my sandy soil.
Many gardeners choose to cut back plants for aesthetic reasons. Mums definitely are not attractive after they freeze, and I can't stand looking at them. So in the fall, I do cut back my mums to the soil. I then add 4 inches of mulch over the top, and they seem to thrive, returning vigorously each spring.
Bluebeards are shrubby perennials. They are supposed to be cut back after they bloom from July to frost then cut back nearly to the ground in spring.
Spiraea is a deciduous shrub, and the way it is handled depends on the type. According to the Sunset Western Garden Book, spiraea, for a loose, graceful look, needs annual renewal of new growth. Old wood that has produced flowers should be cut back to the ground. Prune spring-flowering versions when they finish blooming. Prune summer-flowering species in late winter or very early spring.
If you want to increase your stand of coreopsis or other soft-growth perennials, leave the flowers on at the end of the season until they have released all their seeds. Shake a flower head over your hand to see if there are any seeds left. Once the seeds are released, you can cut back the plants to the ground and place mulch over them.
The decision to cut perennials down or leave the dead growth standing comes down to personal preference.
Another gardener, Maud, asked for the archive site for my articles. Here is a link to Cooperative Extension's garden articles: www.unce.unr.edu/western/news.htm. My articles are under "All Others In Alphabetical Order." You can access current and previous years' articles.
For more information, e-mail email@example.com or call me at 887-2252. You can "Ask a Master Gardener" by e-mailing firstname.lastname@example.org or call your local University of Nevada Cooperative Extension office. Check out many useful horticulture publications at www.unce.unr.edu.
-- JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension.