February 2004 - Indiana Yard and Garden - Purdue Consumer Horticulture

February 2004

Q. I used to have many kinds of peonies with excellent large blooms. But they no longer have many blooms, and the foliage seems to have some kind of disease. I am almost ready to kill them off. What can I do, or should I destroy them? — Diane H. Jungels, Rensselaer, Ind.

A. Cladosporium leaf blotch of peony, also known as red spot or measles, is a common disease in Indiana. Look for distinct, reddish-purple spots that appear on upper leaf surfaces and on stems during early stages of disease development. Eventually, these spots coalesce to form large, irregular, glossy, dark-purple leaf blotches on the upper surface of leaves. The blotches appear light brown or brownish-gray on the lower leaf surface. The merging of spots on stems produces long, reddish-brown streaks.

Although there are fungicides registered for control, none are totally effective at disease suppression. In addition, accurate timing of applications early in the season and the need for thorough coverage and repeated applications make the use of fungicides rather expensive and time consuming for the average homeowner. The best control involves removal of diseased tissue, particularly at the end of the growing season. Stems should be cut at ground level, and the plant material destroyed.

The lack of blooms could be related to another issue. Peonies will not bloom if they are planted to deeply. Yours were obviously planted at a depth that made them happy earlier. Over the years, you may have mulched regularly, mowed grass clippings in their direction or added compost or soil over the crown of the plant. Pull back any material over the crown so that the uppermost buds (eyes) are 1-2 inches below the soil level. If the plants have settled, which will make them lower than the surrounding grade, lift the plants up during the dormant season and reset them at the proper depth.

Other possibilities for a lack of flowers include excess nitrogen fertilizer, which encourages foliage growth at the expense of flower production, or insufficient sunlight. Peonies require at least a half-day of full sun.

Q. I have a question concerning a very timely problem. The deer have been stripping off the branches and bark of small Norway spruce trees and other trees, particularly my small, scented Linden tree. I know that Pruning Seal is not recommended any more after pruning; however, could it possibly help cover up these open wounds? Sometimes, the bark is missing in 1- to 2-foot-long sections, or even all the way around the tree. I am sure I am not the only one with this problem. Your answer could be very helpful. — Alfred Meckel, Bright, Ind.

A. White tail deer can cause damage by stripping bark or eating branches. You can tell their damage from that of a rabbit or other rodent by the edges of the damaged area. Deer do not have front incisors and leave a ragged, torn edge, while rabbits and other rodents leave a clean edge. Also, the damage inflicted by deer is often too far from the ground to incriminate any other animal.

Seals and paints are no longer recommended on tree wounds. They trap moisture against the bark, providing an ideal breeding ground for some insects and diseases. If the wound has any chance of healing, it will form a layer of callus tissue. It cannot do so if a sealing product is applied.

For the future, use plastic tree wrap or woven-wire cylinders to protect young trees from deer and rabbits. Four-foot woven-wire cylinders can also keep deer from rubbing tree trunks with their antlers.

Q. For two years, my yellow rose bush bloomed yellow as it was supposed to do. However, this year, the blooms are red. Do you know why this happened? — Loretta Neidigh, Bloomington, Ind.

A. You are probably seeing flowers coming up from the rootstock. Many roses are grafted onto a rootstock that provides strength, adaptability and more to the plant above. The top portion of the plant is chosen for the aesthetics of the flower and foliage, among other things. A variety of problems can cause the top to die; chief among them is winter damage, but that leaves new shoots coming up from the roots, which could have flowers of a different color. It’s also possible the top portion of the plant is still alive, but shoots from the roots are often more vigorous and may have outgrown the top.

Often, the foliage itself looks different. Inspect it this spring to see if you can identify any shoots coming from the root or below the graft union, as well as a different sort of foliage. Prune out the offending shoots.

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