Gardening Q&A with Richard Nunnally

Q:I have about 17 peonies in a garden. During the second half of every summer, they get black spot. This year, some also got powdery mildew, even though there was no over head watering except by rain. We water with a soaker hose, and the afternoon sun is slightly diminished each year by continued growth by large pine and oak trees. How do I prevent black spot and powdery mildew?

Answer: If those trees are blocking light and air movement in the afternoon, that could be part of the reason for the disease problems. According to the Pest Management Guide from the Cooperative Extension, you can use Immunox or Orthonex for the leaf spot and powdery mildew. If you prefer organic materials, they list neem oil. By the way, fall is the ideal time to transplant peonies, in case you decide to move some of them away from those overhanging trees.

Q:I'd like to know if perennials such as coreopsis, asters and black-eyed Susans should be cut back in the fall or spring? Also, when is the best time to cut back Knock Out roses?

Answer: Fall is a perfect time to cut back your perennials. As for Knock Out roses, they don't require annual pruning like other roses. If yours have gotten too large, you can cut them back in late February, just before they start to make their new growth. They can be trimmed a little after the first frost, but the major pruning should be done after the worst of winter is past.

Q:We live in the country and would like your recommendation on a ground cover for a bank that fronts the road. It's relatively steep, measures approximately 10 feet by 100 feet and we are able to cut it only with a weed eater. This area faces east and receives full sun, but only weeds grow there. We would not be able to water it.

Answer: There are several ground covers that spread on their own -- ivy, periwinkle and liriope. There are also those that don't spread but get larger and eventually cover a larger area -- prostrate junipers.

There are groups that discourage the use of ivy because of its invasive nature. I usually recommend it only where severe erosion is a problem.

Periwinkle and liriope would thrive in the area you described, and both would do fine with little water. You can plant ivy and periwinkle on 3-foot centers in staggered rows, starting at the top of the bank. The liriope would need to be planted on 1-foot centers.

The prostrate junipers would be more expensive and may need some water to get established.

Q:We have had our fig tree for three years, and it has never produced any fruit. It seems the cold does it in every year. We have tried wrapping it in plastic and heavily mulching it, but to no avail. It has grown really well with lots of new shoots, but we cannot seem to keep any of the old wood. It is planted next to our deck, so it seems that it is somewhat protected. Any suggestions on how to winter our fig?

Answer: It sounds like the micro-climate near your fig is not giving it enough protection from the winter winds. Winter sunlight coming through plastic causes the plant to heat up, which stimulates the dormant plant. The night cold damages that part of the plant. The real damage is normally from the drying winter wind.

Switch from wrapping it in plastic to making a frame around it covered with burlap. Make sure it is well-watered going into winter and then use burlap to shield the plant from the wind. This may give you better protection. If the plant still doesn't maintain old wood next spring, you may want to move it to a more sheltered location.

Richard Nunnally is a freelance writer and host of WCVE's monthly gardening show, "Virginia Home Grown." He can be contacted at .