Battling OvergrownWoodland

By Scott Aker
Special to The Washington Post
Thursday, August 6, 2009

Q A wooded area near my house has become scruffy. I have some ivy and vinca there but would like to add another plant. I don't want to go to the trouble and expense of planting; rather I would like to seed the area with a perennial ground cover. What would you recommend?

A The scruffy appearance suggests that invasive plants have taken over. Honeysuckle, multiflora rose, porcelain berry vines, Asian bittersweet and sweet autumn clematis will find their way into a neglected woodland, particularly the edges of woodland adjacent to gardens with invasive plants. For this reason, you should try to contain your English ivy and vinca so they don't spread into the woods.

Deer can contribute greatly to the problem by browsing on the native plants they prefer, leaving a vacuum that aggressive nonnative plants will fill. If deer are not a problem, allow nature to take its course in colonizing the ground rather than sowing seed. The seeds of most woodland plants are not commercially available. Native plants will find their niche if some remain in nearby wooded areas; others, such as ferns, may be dispersed from a distance on the wind.

What fungicide would you recommend for black spot on peonies?

Peonies are afflicted with several diseases in wet weather. Botrytis may cause entire flower heads to collapse and leaves to turn black. Cladosporium is another likely suspect.

It is probably too late for any fungicide to have much effect on the disease. The key to most plant disease problems is prevention, and fungicide is best applied when the infections start -- as the foliage emerges in early spring.

You can reduce the chance of disease next spring by cutting back the foliage when it begins to die back in October. Cut the stems as close to the ground as you can, and remove all traces of foliage from the garden. Get ready for next spring by buying a fungicide labeled for peonies. Several are effective against both Botrytis and Cladosporium. Apply the fungicide when the leaves begin to unfurl and continue to apply weekly until warm, dry summer weather arrives.

I'd like to fertilize my daffodils but don't know the best time of year for this. I am thinking this should be done after they flower but before the foliage disappears so I can locate the bulbs.

Given enough light and the slow release of nutrients from decaying leaves or other organic matter, your daffodils may flourish for decades without your help. If you want to fertilize them, the best time is early spring as the foliage begins to emerge. You can apply a light top dressing of a balanced slow-release garden fertilizer such as 10-10-10, but use no more than a teaspoon per clump of bulbs.

Aker is a horticulturist at the U.S. National Arboretum.

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