October 1995 - Indiana Yard and Garden - Purdue Consumer Horticulture

October 1995

Q: I have a couple of very large tulip beds (700 to 1,000 bulbs), and I usually keep them weeded by hand after the tulips have died down in the spring. Would it be all right to spray the grass and weeds that come up in the beds with Roundup in July or August? It would be a lot easier than hand-weeding the beds all summer. But would this harm the tulip bulbs in the ground? Do you have any other suggestions to keep the beds clean? – Roger Brett, Shoals, Ind.

A: Most pre-emergent herbicides should not be used where bulbs are growing, so you are wise to consider a post-emergent form of weed control. Glyphosate (sold as Roundup or Kleenup) is carried through green plant tissue to the roots. Since it has no soil activity (it can’t move through the soil), you can spray your tulip beds once they are completely dormant and all top growth has been removed. A thick layer of mulch will help reduce the number of weeds.

 

Q: Each year, I plant petunias in my white brick planter in front of the picture window, and they do very well and are pretty until the end of July. Then they get too tall and pull out at the roots and lay over toward the front edge of the planter. Am I supposed to clip them off about halfway down or not? Someone told me I should do this, but I always hate to spoil their looks when they are so pretty. I would appreciate your help. – Mrs. Ken Bolin, Rensselaer, Ind.

A: I know exactly how you feel. Although it’s hard to cut off the few flowers on a leggy plant, you’ll be rewarded with a compact, floriferous petunia. It’s best not to let the plant get so straggly in the first place. Instead, pinch a few stems back each time you remove spent blossoms throughout the summer. I cut mine back quite hard before any summer trips so I don’t miss the flowers.

 

Q: I have two very large Rose of Sharon bushes that are almost 25 years old. They just don’t bloom very much, and they are late. Should I prune them after blooming? What would you suggest? – Hazel Moffatt, Mitchell, Ind.

A: Renewal pruning can rejuvenate the shrubs. Remove one-third of the old, mature stems per season at ground level. After three years, all the branches will be less than 3 years old. Flowering will improve even after the first year. If you don’t mind cutting the entire shrub back at once, Rose of Sharon is one plant that survives having its entire top cut off. Thin the new shoots as they begin to grow to prevent excessive crowding. It’s best to prune when the plant is dormant in late winter or early spring.

 

Q: I would like to know if you have any information as to possible blight on pumpkins. We lost our first pumpkins and squash. They died from the center out, and what we have left are apparently surviving on feeler roots. We are now losing watermelon and late cucumber. Some have been planted in a mixture of commercial cow manure and 12-12-12 fertilizer. Lots of our neighbors have lost theirs. We’ve tried a variety of recommended fungal controls, and they were sprayed regularly. I would like to know for the 1996 season. We had three kinds. – John Glass, Bluffton, Ind.

A: Cucurbits (cantaloupe, cucumbers, watermelons, pumpkins and squash) are susceptible to a number of insects and diseases. If your plant is being attacked by a bacterium or insect (Squash vine borer comes to mind.), it won’t be controlled by a fungicide. Even if it is a fungal problem, a particular fungicide is effective only against a narrow range of fungal pathogens, so until you have the problem properly identified, it’s difficult to recommend a control strategy. Take a sample of the infected plants to your county office of the Purdue University Cooperative Extension Service to identify the problem and get control recommendations.

For a wealth of information on growing cucurbits, ask your county Extension office for copies of Growing Cucumbers, Melons, Squash, Pumpkins and Gourds (HO-8), Cucurbit Insect Management (E-30), Recommendations for Cucumber, Muskmelon and Watermelon Disease Control (BP-18), and Major Blights of Melons and Cucumbers in Indiana (BP-8-2).

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