What to do about our growing weed problems? This week I'll give you the good, the bad and the ugly scoop on your best approaches to weed control around woody perennials, shrubs and trees.
By necessity this is a very short course on the topic. I could write pages and pages on weed control so don't expect all your questions to be answered.
There are two approaches to weed control: preventative and curative. There are also two methods to weed control: hand pulling or hoeing and chemical control.
First let's address the method topic. Obviously, pulling or digging weeds is the safest method of removing weeds from your landscape if you are trying to avoid any damage to your woody plants. But how effective are these methods? The goal is to remove not only the above ground portion but also any root or rhizome material. If you can accomplish this, then mechanical control will be effective but labor-intensive. Make sure you pull weeds before they produce seed. And expect your best results with annual rather than perennial weeds.
Some weeds such as bindweed and what some call whitetop have extensive, deep root systems and cannot be eliminated through cultivation techniques. All that you accomplish will be short lived. But you may also increase the weed spread through these cultivation efforts of deep rooted weeds. Any attempt to cultivate deeper could also damage your nearby woody plant's roots.
There are times when chemical control, through the use of herbicides, is the only effective method. I know some of you out there don't like to use chemicals in your garden, but if you read and follow the label, these herbicides can be used safely. Make sure your selected herbicide can control your target weed and will do so without adverse effects on adjacent plants.
Their main safety problem is not due to adverse impacts on humans or other animals but off-target effects on nearby plants. As Master Gardeners, my colleagues and I are seeing more and more damage to trees and shrubs due to either improper use of herbicides or drift from neighboring properties.
So how can you safely use herbicides? There are a few tips that would be wise to follow. First let's look at preventative control techniques, as they can minimize off-target effects. Pre-emerge herbicides can be used primarily on annuals by preventing seed germination. Just make sure you don't mistime your application. An example of this would be to wait till next year to apply a pre-emerge material for cheatgrass control. Seed from this weed grass actually will begin germinating sometime this August.
Another preventative weed control approach would be to use soil sterilants. I definitely would advise staying away from these! Some of these chemicals can last years and while they might keep your driveway weed free, they could also make your yard a virtual plant desert when the sterilant moves through the soil and zaps desirable landscape plants. Leave these chemicals to the experts!
So what about herbicides you spray on weeds? Well, there are several kinds, but the two most commonly used contain either 2,4-D or glysophate as active ingredients. The herbicide 2,4-D is a contact weed killer absorbed into the leaf tissue and affects only broadleaf plants, not grasses. This is the one we as Master Gardeners see causing the most damage to off-target plants. Affected leaves can have their edges curl up, can take on a thickened, mouse ear appearance and essentially cause leaf tissue deformation. The effect is usually not fatal to larger woody plants. Make sure you don't buy this product if it also contains dicamba. Dicamba has soil activity and can easily damage nearby plants.
Lastly, glysophate is an herbicide that affects plants through green tissue activity and when used properly has no soil activity. Obviously you would not use this to kill dandelions in your lawn unless you enjoy dead grass spots in your turf.
Remember to use contact herbicides on days the wind doesn't blow and early in the day before it gets hot. Keep your spray wand low to the ground and try to spray individual weeds rather than applying a broadcast spray. You, too, can successfully use herbicides safely in your landscape if only you read the label and proceed cautiously. If you have any questions, call the Master Gardener desk at the Delta County Extension Office. Happy gardening.
Jim Leser retired to Cedaredge after a career with Texas A&M University Extension in entomology. He is a member of the Cedaredge Tree Board and a master gardener.blog comments powered by Disqus