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kok328 05-17-2009 08:32 AM

Weed Killer OD
Does anyone have any advice on how to help a tree recover from weed killer overdose?

I hit my lawn hard and early with Weed-B-Gone. I keep forgetting that this is weed killer and not weed remover. So when the dandelions blossomed, I hit it again (extra hard) and now my trees are not looking that healthy.

Nestor_Kelebay 05-17-2009 08:11 PM

Look for a 1-800 Customer Service phone number on your container of Weed-B-Gone, and see if they would agree that the best thing you can do is water the ground around the trees to wash the herbicide down below that 3 feet level or so that the roots extend down.

Also, you want to ensure that you don't walk on that really wet ground much as your compressing the soil with your weight can push the oxygen out of it so that tree roots can drown.

You don't need to know the rest.

Most people aren't aware that a tree's (and most plant's) root system are almost entirely within the top 3 feet of soil.

People see the roots of tiny plants, like grass, and presume that the root system of a large tree is similar, only correspondingly larger, and that's simply not true. When a tree starts growing, it starts with a tap root that penetrates deep into the ground (given the size of the sapling). But that tap root soon develops into a system of LATERAL roots that extend mostly horizontally within the top 3 feet of soil. The root system of a tree extends far beyond it's branches, but the roots seldom extend more than 3feet down.

The reason why is that the nutrients in the soil the roots are intended to absorb require the aerobic decay of organic matter (compost, if you will), and you only have enough air in the soil for aerobic decay to occur within a few feet of the surface. Deeper than that, you don't get enough air in the soil for aerobic decay, and things don't rot. It's the rotting of organic matter that produces the nutrients that plants thrive, and that makes the soil fertile. Below that top thin layer of fertile soil, there is no aerobic decay and roots that grow into that deeper soil stop growing because they're not finding the kind of soil the tree likes.

That's the same reason why they can harvest 200 year old logs from trees that were cut down in the 1800's and have been sitting on the bottoms of lakes for literally two centuries. The water deep down doesn't have enough oxygen in it for that decay to occur, so even after 200 years soaking wet, the wood won't have rotted.

This is also the reason why it's comparatively rare to have tree roots growing into a sewer pipe given the number of trees in our cities and their proximity to sewer pipes. The tree roots are almost entirely within the top 3 feet of soil where aerobic decay occurs, but the sewer pipes are much deeper where there is no aerobic decay and there are far fewer nutrients in the soil.

Trees can also grow anchor roots that do extend deeper into the ground than the roots that nourish the tree, but these anchor roots don't grow very deep as the tree grows taller. It's primarily the "feeder" roots that grow horizontally away from the tree that anchor the tree so that it can resist wind.

This web page (from the City of Winnipeg's web site) contains the following:

About trees, tree roots and sewer pipes:

Roots from trees growing near sewer lines do not actively penetrate sewer pipes and cause blockages. Roots gain entry through previously cracked portions of sewer pipes. Sewer pipes inevitably deteriorate through old age or separate and crack due to ground shifting and heaving.

Sewer pipe is laid approximately 2 metres, or more, deep.
The only tree roots at that depth are anchor roots, as the finer and fibrous feeder roots are located within the first metre of soil.
Anchor roots can co-exist with intact sewer pipes indefinitely without causing blockages.

A sewer line leak allows sewage and air to escape into the soil, creating a ratio of air, water and nutrients at that depth that becomes similar to those found near the surface. Anchor roots at the site of the leak produce very fine, opportunistic feeder roots that can enter the sewer pipe.

And, Winnipeg ain't no dry desert like Las Vegas or Phoenix. I got trees growing on or near my property that have trunks 3 feet in diameter and are better than 40 feet tall. It's hard to imagine that the root system of such trees only extends down a few feet, but what we expect and what we discover has always been a source of amazement and opportunity to us.

It's entirely the fact that despite their large size, a tree's roots are almost entirely in the same top 18 inches of soil that you "hit hard" with weed killer that's affecting the health of your trees.

BigSis 06-18-2009 08:37 PM

great info Nestor, thanks!

slownsteady 06-22-2009 05:59 PM

Read your container of Weed-b-gon. The stuff is supposed to work down through the leaves of the weeds you spray it on. It should be inert on contact with the soil. So unless you are spraying the leaves of your trees, you might want to look for a different source of trouble for your trees.

jimmy4 06-25-2009 03:56 PM

I would recommend using an organic fertilizer or weed killer in the future. The problem with chemical fertilizers (in addition to polluting lakes, streams, water tables and drinking water supplies) is that they tend to kill the living organisms in your soil. Over time, the chemicals essential "neuter' your soil. The only nutrients your plants and grass then receives is from the chemicals you are adding - which will require more and more over time. Also, the chemicals don't promote nearly the root development that organic fertilizers (or good 'ol compost) do and therefore your lawn and landscaping will require much more water during the hot and dry months than an area treated organically. Plus, if you have children that play in your yard, do you really want them rolling around in a bed of chemical residue? I realize that to some this may appear extreme but I would challenge the skeptics to google some of the ingredients on the back of chemical fertilizers and pesticides to see what I am referring to. I treated the yard/landscaping at my last home with chemicals and then a friend turned me on to the benefits of organic treatments. I tried them at my new home and the results were dramatic! I will say that the chemicals give the plants a faster and more noticeable initial 'pop' but over time don't even compare to the plant quality of an organically treated yard. Hope you find this information helpful.

kok328 06-26-2009 04:39 PM

Heavy rains and some tree fertilizer have seemed to save the tree but, now the japanese beetles are shredding the leaves. I had the same problem last year and thought it would die from the beetle damage. I treated MY lawn for the beetle larvae but, those damn things won't respect the property boundaries.

DaringDamsel 06-27-2009 03:51 AM

I really think that they should require accurate labeling on these products. There is no such thing as a WEED killer. These chemicals are PLANT killers. The best way to control weeds is to grow healthy plants. Weeds are a symptom of a problem. Try to find the underlying problem, and treat that. (Though you will still need to take care of the weeds, once they are established.)


slownsteady 06-29-2009 09:52 AM

It sounds like the orig. post was caused by treating the whole lawn with weed killer, possibly by hooking it up to the lawn sprinkler or hose. It's a real good idea to treat weeds selectively. Get a pump-up sprayer, mix up a small batch of weed killer and walk around your lawn spraying just the broad-leaf weeds. Yes, it takes a little time and a little more effort, but it's much safer, more economical, and you get to be outdoors in your beautiful yard!

Actually, Jimmy4 has some real good advice posted above.

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