Northwest Arkansas Democrat-Gazette
In the garden
QYou dodged a specific question that a writer posed recently in the letter beginning “Emergency!” The issue is about iris beds and whether Roundup will kill the bulbs. Although you mention daffodils in your column, please correct your silence concerning irises. It’s a question I’ve been hoping you’d answer for some time. Is there any other product that could be used in iris beds? Recommending a hoe to a letter writer who has conceded that she/he no longer has the physical capacity to weed was also something of a dodge!
AI did not mean to dodge. I did say that I don’t recommend spraying Roundup on anything other than what you want to kill. Roundup should not be used in contact with iris rhizomes or foliage. If you choose to use Roundup you would need to shield the desirable vegetation while spraying. Although Roundup may not always outright kill an iris if it was sprayed, it would do damage and can distort the foliage. Some pre-emergent herbicides are fairly effective on annual
broadleaf weeds. They must be applied before the weeds emerge in the fall or early spring for winter and summer annual weeds. Surflan and Treflan are both labeled for irises. There is nothing that will prevent perennial weeds or grasses. Bermuda grass tends to be one of the worst weed problems in iris beds, and the post-emergent grass killers — Poast and Fusilade — do a good job but should be applied before the grass has thoroughly taken over.
Q I have some old azaleas that have stems turning dark with small white specks along the stems. I do not see signs of lace bugs on the underside of leaves. I am feeding now with a fertilizer with a systemic insecticide. Any suggestions?
A It sounds as if you have azalea bark scale, a very similar insect to the crape myrtle bark scale. The black is from the sooty mold that forms on the honeydew given off by the insects. The white specks are the insects. The fertilizer combined with systemic insecticide should do the trick.
Q I have a question about our doublefile viburnum. It used to be a full and healthy plant, but it began to look stressed two summers ago. I would water it but apparently not enough. The only healthy growth now is on the lower left. It did have leaves and a few anemic flowers this spring but they quickly dropped off. What should I do?
A I would say a Hail Mary and cut out all the dead growth. It is going to leave a pretty small plant, but water and fertilize and then see what happens. If it still looks bad next spring, pull it and replace it. My new motto is life is too short to live with bad plants.
Q Can you stand one more Bradford pear tree question? We have a volunteer tree in our backyard that I thought was a crabapple. It has three or four small trunks and is 20-25 feet tall. I plan to have it cut down soon. After that is done, will there be little saplings that come up from the roots, and if so how can I finally kill it off?
A I commend you for removing the ornamental pear tree. Once it is cut back, treat the stump that is left with Brush-B-Gon, Brush Killer or Roundup Super Concentrate. Apply the products undiluted for stump treatment. A cheap, one-inch paintbrush works well for this purpose. Apply the herbicide right after you cut the tree down to allow for as much uptake as possible. Q This fuzzy looking polka dot growth is on the end of a leafless oak twig. I’ve never seen one like it. Do you know what it might be? [The reader provided a photo.]
A This is an oak leaf gall. This particular gall was probably caused by a gall wasp. The adult lays her eggs on the leaves and when the eggs hatch, the larva gives off an enzyme that causes these unusual shapes on the leaves. They can come in many colors and can be solid or spotted. While they look unusual they don’t cause much harm to the trees. While most galls are produced by insects a few are caused by fungi.