AUGUST
2009

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

09-03-09

Question and Answer

Q. The last approximately six years have been disastrous for my two cherry trees. The first year, I thinned out the fruit and harvested a light crop. The second year, I had an abundance of fruit but, after a few weeks, all the leaves fell off. The fruit stayed, and I harvested a good crop. The next year, the trees lived a short time and then died. This same thing happened three years before -- the same process. Both trees are planted side by side and both reacted the same way. All my other trees are doing great: peach, pear, three types apples and persimmon.

My plum trees got very hard black crustaceans, which killed out some of the limbs, but I plan on replacing them also. This fungus, or whatever, affected other trees on my property. Somebody told me not to plant a new tree in the same hole I removed the infected tree. Is this true? I hope you can help me out on some of these problems.

A. You don't mention what varieties of cherry trees you've tried, but my best guess is that winter injury was the primary culprit. Sweet cherries are generally less hardy than many of the other fruits that you are growing -- only a few varieties are hardy enough to withstand Indiana winters. Tart cherries are hardier than sweet varieties. You'll find a description of recommended varieties and other growing information in the Purdue Extension bulletin "Growing Cherries In Indiana" www.hort.purdue.edu/ext/HO-9.PDF.

The black "crustaceans" on your plum tree are galls, caused by the black knot fungus. The disease also attacks cherry trees but tends to be more damaging to plums. The fungus enters young twigs, branches and fruit stems, causing abnormal growth and swelling of bark and wood. The galls enlarge quickly into a black hard knot that girdles the twig/branch, causing it to dieback and also releasing spores that spread the disease. Prune out the galls as soon as they are noticed, cutting back several inches below the gall to a healthy bud or side branch. This is not a root disease, so I don't think it will be a problem to replace the plum trees in the same location; however, black knot will likely continue to be a problem on the new trees as well. A dormant lime sulfur application just before the trees begin spring growth can help prevent the infection.

Q. I have two, 2-year-old 'Belle of Woking' Clematis. One of them had two flowers in the spring but has had none since. They have been fertilized. The two flowers it did have were big and beautiful. It gets 4-5 hours of sun a day, and they are shaded at the bottom. The vines are 9-10 feet climbing up my arbor. One vine that hasn't flowered has no branches, and it just grows straight up.

A. 'Belle of Woking' is a lovely double-flowered Clematis of the type that blooms on both old and new wood. The early flowers come from buds produced on last year's growth and are the largest blooms. Smaller flowers later in the season develop on the new shoot buds that form in the spring. Pruning is the key to a good display of blooms on these types and must be done one stem at a time. In early spring, look for the swelling of new foliage buds, could be a foot or more below the top of the vines. Prune out the dead stems above these buds. If the vines have become overgrown, you can wait until immediately after the early spring flowers, then cut the plants back hard by a third or more. The plant that is growing straight up with no branches will need to be cut back hard next spring, to about 12 inches above the soil, to promote branching. You will, of course, sacrifice the large spring blooms next year, but the plant will perform better in coming years.

Q. My husband and I bought a rhododendron as a second anniversary gift to each other and planted it in an unfavorable spot. Fortunately, we noticed it wasn't thriving in time. We replanted it, and it grew nicely for a few years. In the spring of 2008, I tried to use landscaping cloth under it to stop the weeds and a fungus formed under the cloth. The fungus harmed the bush, but we noticed what was happening and removed the cloth in time. This year, many of the leaves have turned black. Do you have any idea what is happening? Can we save the bush? How can we mulch under it safely?

A. Although it is possible that the fungus is causing the damage, I'm more inclined to think that the overly moist, poorly aerated conditions under the fabric mulch led to root rot/suffocation. We had a particularly cold, rainy spring and early summer this year, so this too could have aggravated the situation. If mulching is desired for weed control, use a shallow 2-3 inch layer of bark chips or similar material. Keep the mulch pulled back away from the trunk of the shrub. If the foliage is continuing to turn black, you should consider submitting samples to the Purdue Plant and Pest Diagnostic Lab, http://www.ppdl.purdue.edu.

 

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,