January 3, 2007

Overwatering Can Lead to Problems With Dogwood Trees GARDENING Q&A

Q. Regarding a dogwood tree in a recent column, the writer said they were watering a stressed tree. But if they were using sprinklers and a hose, they were creating a moist environment. This would be ideal for a fungus and bacteria to enter the tree. The problem might even be anthracnose. Bark and stems would show problems, plus the flowers and leaves. - D.C. Taylor, Outer Banks, N.C.

A. Your letter was written in pencil on a card and I hope I interpreted it properly. Virginia Tech tree authority, Bonnie Appleton at the Hampton Roads Research Center, said, "Overwatering could cause problems with dogwoods. They don't like wet feet, and that could predispose the trees to other things, like anthracnose. If these trees are dogwoods, the pathologists are still saying that its too hot in Hampton Roads for the Discula anthracnose fungus to live."

Q. I noted your column and the advice you gave a lady from North Carolina about Siberian irises. As an AIS member/judge and a local Siberian iris grower for 25 years - as well as having grown more varieties in the Hampton Roads area than anyone else, I disagree with your advice.

Many people make the mistake of wanting to treat all irises as bulbs, and this is one of the major reasons they don't do well. Siberian iris like a soil rich in composted organic matter, slightly moist but no standing water, especially in winter. The soil should be slightly on the acidic side although they are adaptable to a wide range of soil pH. Most of our soils are either neutral or on the acidic side.

I lightly broadcast 10-10-10 granular fertilizer in early February and that does well for me. Siberian iris start growth early in spring, and I feel this gives them a boost. I then use a liquid fertilizer (Miracle Gro) on them, starting in early March. As to cutting the leaves back, I do that in late fall after they die back. They start sending up new growth in early February, and you definitely do not want to be cutting them back then.

There is an excellent book for any iris grower called, "The Gardeners' Iris Book" by William Shear. It can be ordered online from the American Iris Society's Web page. Shear teaches at Hampden- Sydney College, so his recommendations are good for the Hampton Roads area. At the Fred Heutte Center in Norfolk, we have some limited starts of Siberian iris, "Caesars Brother." They are potted and free on a first-come, first-take basis. Call the Heutte Center at (757) 441-2513 for further information. - Bill Smoot, Portsmouth

A. In my advice to the Siberian iris grower I recommended 10-10- 10, the same as you recommend. As to cutting the foliage, it's important not to cut off new foliage but to cut off the old, after it dies down. Your response should give the inquirer enough more information to grow beautiful Siberian iris.

Q. A vine came up ln my yard that looked interesting so I planted it in a flowerbed. It has become so invasive that it has taken over the flowerbed, has run up onto the deck and has even come through the cracks in the deck. It is light green in color. The leaves and stems are rough and feel almost like briars. I keep hoping that I will see a flower appear but everything that looks like a bud turns into more vine. Can you help identify it? - Alice Wellons, Shawboro N.C.

A. Our plant identifier, Mike Andruczyk, says your vine looks and sounds like Humulus lupulus or Hops vine. It does not flower until late summer or fall and then the bloom is not showy.

It is definitely aggressive, he says, but can be used as a ground cover.

It's also used to make beer.


No gardening questions are taken over the phone. For a faster reply, e-mail [email protected] and include your city. Or, write to Robert Stiffler, The Virginian-Pilot, 150 W. Brambleton Ave., Norfolk, VA 23510. Fax to (757) 446-2963. Limit letters to one or two questions.

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