Q: Can you cut iris plants down after blooming? -- Tim Bryan, email
A: Not if you want many flowers next year. The green leaves gather energy during summer to make flower buds next spring. I see some iris gardeners cutting their leaves into a fan shape, but the only time this is appropriate is after dividing iris clumps.
Q: I heard you talking on the radio about finding diatomaceous earth to use for bugs in the garden. I bought the stuff from a pool supply store, where it is cheap! -- Multiple listeners
A: Unfortunately, diatomaceous earth (D.E.) for pools is not the same as diatomaceous earth for insects. Diatomaceous earth originally comes from the "shells" of tiny sea creatures. The "shells" were deposited at the bottom of extinct shallow seas, and the mineral is now mined for use in many products.
The pool product has been heated, turning much of the silicon dioxide in the mineral into crystalline silica. This makes it great for filtration but very dangerous for human exposure. Breathing the dust can lead to silicosis of the lungs and possibly cancer.
The particles of unheated insecticidal diatomaceous earth have very sharp edges. When an insect walks over them, the particles cut the insect's skin, causing it to dry out and die. Insecticidal D.E. can be effective if applied where insects crawl or congregate. Though it’s dusty, it contains a very small amount of crystalline silica. I recommend you stop using the pool-grade product.
Q: I had two huge pines taken down after they were stricken with beetles. But even after raking and picking up small limbs, I have pine debris all over my plants. I am concerned the pine acid will kill everything. -- Judy Daniel, Johns Creek
A: It's a myth that pine straw and chips acidify the soil any more than any other tree or soil amendment. I wouldn't worry about it. Let nature take its course.
Q: A friend of mine in Savannah gave me several male and female pecan trees. Will they thrive here? How do I identify a male from a female tree? -- George Walker, Mableton
A: Pecans don't have male and female trees. Many pecan varieties, however, shed pollen at a different time than their flowers are able to receive it, making for marginal nut set some years. That's why it's good to plant two varieties. If you don't know exactly which variety you have, it's impossible to predict its pollination pattern. If the pecans grew from nuts on your friend's property, it's also impossible to predict how large the nuts will be or how resistant to disease they will be. It takes at least five years for a pecan to bear its first crop. You can plant the pecans now if you're willing to wait years to see whether your experiment pans out. Or you can buy and plant named superior varieties such as 'Stuart,' 'Elliott,' 'Gloria Grande' or 'Sumner.'
Q: Our 19-year-old son has expressed an interest in double majoring in history and agriculture. What are some examples of jobs/career paths that we can visualize, besides farming? -- Jill McKenzie, Forsyth County
A: The University of Georgia's Faith Peppers says there are nearly twice as many available jobs in agriculture as Georgia has graduates to fill them -- quite a good situation in this economy. Graduates also have some of the highest starting salaries of any college at the university. To see examples of career opportunities and the Dean's Promise program that supports internships and study-abroad experiences, go to xrl.us/agcareers.
Listen to Walter Reeves on Saturday mornings on AM 750 and 95.5 FM News-Talk WSB. Visit his website, www.walterreeves.com, or join his Facebook fan page at xrl.us/wrfacebook for more garden tips.
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