AUGUST
2011

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

08-04-11

Question and Answer


Q. I have 5-7 peony bushes that have large black spots on the leaves. Last year, and also this year, I did not have very many blooms on these older bushes. Could you tell me what is the cause of these black spots and how to remedy this problem?

A. Peonies in Indiana are quite likely to develop a fungal disease called leaf blotch, also known as red spot and measles. Discolored blotches (lesions) occur on leaves or stems and may start as tiny red spots ("measles") but eventually progress to larger brown or purple blotches. It is not unusual for the peony plant to be completely defoliated from this disease by the end of summer, but, surprisingly, the plant seems to be able to tolerate the infection. The fungus survives the winter in infected plant debris and produces spores in the spring, which are then splashed onto young foliage and stems through rainfall or overhead watering. Remove dead plant residue in late fall or early spring before new growth emerges to reduce the severity of this disease next season. When possible, use drip irrigation to minimize fungal infection. The Purdue Plant and Pest Diagnostic Lab has additional information on peony leaf blotch at http://www.ppdl.purdue.edu/PPDL/weeklypics/8-20-07.html.

Q. I have a peony bush that I transplanted from a very shady spot to full sun. I did this about 3-5 years ago. The bush is getting larger and fuller but has not bloomed. There was one small bud on it this year, but it did not develop. Is there a way I can make this bloom?

A. You may have set them too deep, or perhaps they have been heavily mulched? Peonies planted too deep will produce foliage each year, but they may never bloom. The buds of the tuber should be set no deeper than 2 inches below the soil surface. More information on growing peonies is online at http://www.hort.purdue.edu/ext/ho-76.pdf.

Q. I want to know about tomatoes. To keep the plants from getting so tall and spindly, I think I've read that pinching the top of them out would make them bush out more so they produce more tomatoes and better quality ones. If this is true, when and how do you go about doing the pinching?

A. Tomato plants are classified by two types of growth habit. Determinate tomatoes generally stay more compact because they grow foliage first, then set flower clusters on side shoots and the terminal shoot, at which time the plant stops growing taller. Determinate tomatoes tend to set all of their fruit at about the same time and therefore have a more concentrate harvest.

Indeterminate tomatoes continue to grow and produce flower clusters in the side buds. The terminal bud continues to produce additional foliage indefinitely at the terminal, so these plants get very tall. You could prune out the tip, but you will end up reducing your overall yield by doing so. Some gardeners like to do this toward the end of the growing season, about 3-4 weeks prior to expected frost to reserve plant resources for the fruits that have already set.

If your plants are routinely taller than what you prefer, consider planting determinate cultivars next year.

tree leaf and seed pods

Q. I have seen catalpa trees with long pods; however, I have a tree that has most features of the catalpa with the exception of nut-like pods. Can you please identify this tree? The leaves are about 6-8 inches wide; nuts are about 1 inch and very sticky when cracked.

A. This tree is known as the Royal Paulownia or Empress Tree, Paulownia tomentosa, and is NOT related to Catalpa. The fruits are capsules that open to release many winged seeds in the fall. In northern Indiana, Paulownia dies back to the ground each winter and resprouts the following spring, with rather impressive annual foliage growth. The tree may form what appear to be flower buds, but it does not flower, and I have never seen it fruit this far north. I have seen it in full bloom while traveling elsewhere, and it is rather pretty in flower. It can be a messy nuisance with dropped flowers and seeds and is considered invasive in many areas where it is hardy.


 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,