Controling Weeds around Urban Landscapes


Controlling weeds around trees is very important
to ensuring that you have a shortened establishment period, especially for young trees. Weeds
and grasses along the base of young trees really lengthen your establishment period.
They compete for water, they compete for nutrients and can make your establishment period longer
which can make the period of time that you have to water and maintain those trees last
that many months longer. The other problem we have with allowing weeds and competition
to grow around the base of the trees is we end up with conflicts with both mowing equipment
and string tremors. Often times, mowing equipment is tempted to get too close to the tree as
the operators try to cut that grass that is growing right up at the base of trees. When
this happens, they invariably nick the side of trees. When trees are nicked, oftentimes
this will lead to pockets of decay. It allows for certain diseases and fungus to become
established. This can affect the overall health of the tree but can also lead to structural
problems. Overtime this rot can lead to weakened points in the tree where trees can snap in
storm events. Now the very same thing is also true for string tremors. Invariably, if the
mower doesn’t tend to nick the tree, a string tremor is brought in and when that string
strikes the side of a tree, invariably it will wound or bruise the cambium that’s just
underneath the bark. This is especially a problem in thin-barked trees and especially
in young trees. Now there’s two methods to control weeds around the base of trees. One
is using mulch. We already talked about the benefits of mulch and another benefit that
they will have is they will help suppress a lot of the weeds and grasses and thus not
having string tremors or mowing equipment getting so close to trees where they damage
them. Another technique that can be used to control weeds and grasses around trees are
herbicides. A good herbicide that can be used is Glyphosate, oftentimes known as RoundUp.
While it has a low toxicity to humans, we should always follow the label and ensure
that we use the proper personal protective equipment. You ought to use long sleeve shirts.
You ought to use protective eye wear. You ought to use herbicide-safe gloves, shoes
and socks as well as long pants. What you’re trying to do is avoid from having those herbicides
come in contact with your skin. A few other things to note when you’re using RoundUp.
RoundUp is a foliar active herbicide, meaning that anything that is green or anything that
translocates or photosynthesizes will absorb the chemical and affect the tree. So we do
not want to get RoundUp on any of the leaves of trees or any off-target vegetation such
as grasses. So when we’re trying to avoid off-target issues, we want to make sure that
we select a day spray where there is low wind. When we have windy days, oftentimes as the
spray comes out the end of the nozzle, it is picked up and we get drift and when drift
occurs, you may end up having the drift land on other vegetation, whether it be your grass,
shrubs, or other trees that you did not intend to spray. So select days that have low wind
to ensure that you don’t have this issue. You can also affect that same issue by adjusting
the nozzle by the size of the droplet that’s coming out. On days that may have a little
bit more wind, you can adjust it and have a larger droplet which will have less of a
tendency to drift on those windy days. Another thing to consider when you’re spraying around
trees is you do not want to spray the bark of the tree. There’s always the possibility
that the trees may translocate the herbicide into the tissue and cause herbicide damage.
Additionally, if you have any wounds at the base of the tree, this could also have the
potential to translocate that herbicide. So caution ought to be taken to also not allow
the herbicide to come into contact with the base of the tree. Now one way that can be
used to do that is to use a simple piece of cardboard, which as you’re spraying, place
it at the base of the tree so that none of the spray can actually come into contact with
either the base of that tree or any large exposed roots. So right now, I’m just going
to control some of the weeds around the base of the tree. So if you’ll note I have some
of my personal protective equipment on. I’ve got my safety glasses, gloves, long-sleeve
shirt, long pants, shoes and socks, and so as I spray the base of this tree, I want to
control a lot of the weeds, much like when you’re doing mulch, you want to be able to
have a ring around the tree usually, preferably about four to five feet out and you control
the base of the tree, controlling these weeds. Keep the nozzle fairly close to the ground
so you can avoid drift and as you get closer to the tree you can use something like cardboard
to avoid wetting the side of the tree as you spray that area. When controlling weeds around
trees, mulch is the preferred method. It not only puts down the nutrients we need with
the organic content, but it also controls those weeds. Herbicides really should be used
as a secondary method and oftentimes to control some of the weeds that may come through our
mulch layer. This avoids us getting too close with the spray to the trees and possibly seeing
injury due to spraying leaves that may be close to the ground or having some of the
herbicides from glyphosate be translocated through a wound or a thin-barked tree species.

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