More recent landscape questions and answers

Horticulture

Pruning damaged Japanese maple

My Japanese maple took a beating from the cold spring temperatures. Now it is growing back above the grafted area. Should I go ahead and cut back the dead branches? How far back should I cut. It looks dead until you get towards the center branches. I don't want to hamper its growth but it looks like some of the dead should be cleared away so it can grow.

I recommend cutting each branch back to a point just beyond where a healthy looking shoot is growing, trying not to leave stubs of dead wood. It will take several years of detailed pruning to retrain the tree into an aesthetically pleasing form. There will be a proliferation of shoots just behind the points of dieback. You may want to thin a few of these out during the summer by cutting them off back to the main stem to begin the training process. You can cut out the dead wood and start your shaping now. However, I would wait until next spring to do serious pruning. Do not prune in late summer or fall, since this may make the tree more susceptible to winter injury.

Chris Starbuck
State Extension Specialist
Woody Ornamentals

Brown leaf tips

My golden pothos is getting brown spots on the leaf tips. What could be causing this?

Browning at the tips of the leaves is indicative of a water relations problem in the plant. This can be caused by a number of things including excess salts in the growing medium or the use of water that has gone through a water softener.

David H. Trinklein
Department of Horticulture

Diseased zoysia sample

I have brown spot on my zoysia lawn. I have been on your Web site, and still can't figure out what is wrong. I have just about ruled out a fungus or an insect. Some years ago I sent you a sample from a sick tree and you correctly analyzed the disease. Would it be possible to send you a sample of my diseased zoysia?

We would be happy to take a look at your zoysia sample and provide you with a diagnosis of the problem and management information. The MU Plant Diagnostic Clinic Web site has specific instructions for turf sample submission and a more complete listing of services and associated fees.

What to send to find out what's wrong

Include a healthy example for comparison when possible.
Include enough of the plant to clearly indicate whether the symptoms are occurring on old or new growth.
Above ground symptoms often result from a problem occurring in the lower stem or roots, so it's best to send entire plants when feasible.
Dig plants to leave roots intact in a soil ball and prevent drying.
With larger specimens, try to sample from the transition zone between healthy and affected tissue.

Special instructions for turfgrass

Take plugs at least 4 inches across with a cup cutter or knife to a depth to include the roots.
Always include a diseased plug, a healthy plug, and one plug from the transition zone between healthy and affected turf.

Simeon Wright
Plant Diagnostic Clinic Coordinator

Grass in iris bed

How can I get rid of the grass that has invaded my iris plants? The clay soil here makes it impossible to pull up the grass by the roots, so it keeps coming back. I have mulched my plants, but last year I could not give the irises the attention they deserved and the grass has really taken hold in my beds.

There is not a good solution for this. Many, including myself, end up digging the iris bed up and killing off the grass, then replanting the iris in the bed. Some selectively spray Roundup as best they can on the grass, trying to avoid the iris. Just trying to do continuous weeding will help you eventually get ahead of the grass, but this is labor intensive.

You can use a brush and actually paint onto the grass blades, and this will kill the grass. It takes several applications and is something you need to keep up with.

Mary K. Kroening
Horticulture Specialist

Insects eating stems off tomato plants

There are black, flying insects about 3/4-inch long eating the stems off all my tomato plants. They look like wasps with long legs. Can you tell me what they are?

I am not familiar with an insect that looks like a wasp that would eat leaves and stems off of tomato plant. Some wasps may be present preying on insects that do feed on tomatoes. You might check the leaves and stems closely for insects that are well camouflaged and may be causing the actual damage, such as the tomato hornworm, a green caterpillar that blends in with the surrounding foliage.

Simeon Wright
Plant Diagnostic Clinic Coordinator