The first snow of the season catches everyone with tasks undone. This winter is no exception. Weeds are still growing underneath the snow, and the worst problems never die naturally. The last chance to control serious weed problems will be when the snow melts and gives one final chance to spray.
Frost marks a significant change in metabolism of perennial plants. Some are killed with the first frost, but others only go dormant and return season after season to haunt us in the garden. This Halloween season reserve time to go after those weeds that are real garden spooks. This rogue's gallery includes field bindweed or wild morning glory, quack grass, white-top, Canada thistle and many others. These deep-rooted, long-lived weeds get worse and worse each year.Ignore chemical controls for any annual weeds. These died with the first fall frost. Pull and discard any that have gone to seed. Reserve chemical treatment for persistent, obnoxious pests that return year after year.
Plants spend most of the growing season moving water and nutrients from the soil to the leaves. This begins when growth starts in the spring and continues until the frost triggers a reversed process. When that signal comes, plants move nutrients in leaves down to the roots for storage. Successful weed control uses the knowledge of plant physiology to control problem weeds.
The tops of perennials die when the weather gets cold and frosty. The roots remain alive and store nutrients so the plants can regrow next spring. Unless the roots are destroyed, the plants continue to grow and spread and damage your garden next spring. Since nutrients move down to the roots in the fall, the way to destroy the plants is to destroy the roots. Piggyback herbicide sprays onto the nutrients moving downward to destroy the roots and prevent return growth next year.
Plant condition is critical in successful weed control. Some gardeners erroneously suppose that weeds that are nearly dead are the most likely to die when sprayed in the fall. Unless the tops are still green and in good condition they will not absorb herbicides. Timing is critical. Spray too early and the plant is still pumping water and nutrients upward. Delay too long and the leaves are dead and brown and will not absorb herbicides.
Roundup and Killzall control grassy weeds. Both contain gly-phosate and are non-selective herbicides. This means they kill any plant they contact. Protect desirable plants by covering them with plastic sheeting or cardboard while spraying or by carefully directing the spray only at weeds. These products are also effective against many broadleaved weeds. They kill desirable plants just as well as weeds so use them carefully.
Selective weed control is possible with some products. They come in two categories. They come in two categories. Broadleaf weedkillers kill dicotyledons. These plants have two seed leaves and palmate or spreading leaf veins. They do not affect grass at recommended rates. Grassy weed killers control monocotyledons. These plants have one seed leaf and parallel veins. They do not damage most dicots.
Broadleaved weed killers include 2-4,D, MCPP, garlon, di-camba and several others pro-ducts. Homeowners are most likely to buy Trimec, which is a combination of the first three listed products. Many broadleaf weedkillers are available under many brand names.
Selective grass killers contain fusilade or Poast. These products kill grass, but selectively spare the dicotlyledons. Brand names containing fusilade include Grass-B-Gone, Over-The-Top and Orn-a-mec. Poast is available as High-Yield Poast.
Add some extra surfactant to help keep the herbicide on the leaves until it is absorbed. Surfactants are spreader stickers that help the spray spread over the leaves and stick to them until they are absorbed. This is critical because they cannot get down to the roots without going through the leaves.
Certain unwanted woody plants including Siberian Elm, Russian Olive, poplar and willow can be effectively controlled at this time. The preferred methods are stump or frill treatments. Cut off the sprout and paint it with one of the nonselective or broadleaf weed-killers. Paint the cut areas with the concentrated herbicides straight from the bottle as soon as the cut is made.
The frill treatment is a similar method. Make a series of downward chops with an ax or hatchet at the base of the stump. Pour a small amount of the concentrated herbicide into each cut as soon as it is made. This will translocate to the roots and kill the unwanted sprouts.
When the garden fades, go after persistent, perennial weeds. Small efforts now will prevent major problems next year. Many perennial weeds are still green and growing. Take advantage of a warm day when the snow melts to control these problem weeds.
*****
ADDITIONAL INFORMATION
Orchid Society autumn show Nov. 2-4
The Utah Orchid Society is holding its autumn orchid show at Red Butte Garden's Cottam Visitor Center on Saturday, Sunday and Monday from 10 a.m. to 5 p.m.
The show is free to Red Butte Garden members. Adults are $3. Children over age 4, students and senior citizens are $2. University of Utah students with valid student cards are free. The show was planned to fall on one of the garden's "Free Mondays." (No admission is charged the first Monday of every month at Red Butte Gardens.)
Certified judges from the American Orchid Society will jury the competition, and the Orchid Digest Society will present awards for the best arrangement and the best set-up in the competition.