Protecting trees from String trimmer

Question

I use a string trimmer extensively on my property, but to date I have avoided using it around the foot of trees because I'm worried it will do damage to them.

Recently I used some off-cut of plastic tubes to protect the bases of my small trees, but I'm not sure what to do about more established ones - like palm trees and apple trees with > 10cm diameter trunk, so a couple of questions -

1. How damaging is a (7000 rpm, petrol driven) weed wacker to trees ? (It makes short work of even fairly thick stemmed weeds, but I assume trees are made of tougher stuff as they take longer to grow)

2. How can I protect the base of larger trees

Answer 1

In the long term you could easily do enough damage to kill the trees.

The "active" part of the trunk transporting fluids between the roots and the branches is close to the outside of the tree, just under the bark. Any local damage to the bark can affect that process, weaken the growth of the tree, and also allow pests and diseases a way in.

Stripping off a narrow ring of bark right round the trunk is almost guaranteed to kill any tree, however big it is. That is why protecting trees from damage from rabbits etc eating bark in winter is so important.

If you can't get plastic tubes big enough to protect the trunk, try the wire mesh protectors used to keep animals from causing damage. They should be strong enough to stop you accidentally hitting the trunk with your weed whacker, and the noise made when you hit the wire mesh will warn that you are getting too close.

Answer 2

I follow the mulched circle method, where I use a collar about 18" wide around the tree, mulched with shredded bark or wood chips. You have to re-do the mulch every spring, but the advantage here is that you don't have to get close at all to the trunk with your mower. If you do this, you want to make sure that you don't "volcano" the mulch around the trunk - it should at most just "kiss" the bark and be rather shallow for the first several inches from the trunk and then rise from there, tapering to the outer edge.

There are drawbacks, of course - some mowers will kick out the bark (depending on deck height, usually, and whether it's a mulching mower) and as mentioned, you have to rejuvenate the mulch every year. You can avoid the kicking out by just putting the tires of the mower on the mulch (works best with a riding mower because of larger tires).

I've also seen people surrounding tree trunks with perennials like violets and hosta, or larger groundcovers like epimediums. I don't like using hosta myself because in my area they attract enormous numbers of slugs.

Answer 3

The bark is not a living part, so you may touch it softly.

Rub and plastic are also not ideal (humidity, insects hiding, which could also weaken or damage the inner part).

So it is not easy. You should estimate what it is better for you and monitor your choice, and eventually go back.

On professional orchids I saw three solutions:

• a sort of trimmer, but it turns slower, and there are mechanical protections (and springs). This is the preferred way if there are suckers.

• a sort of lawn mover (also with mechanical protection and spring). But just cutting below, it offer protection. Having the plants in rows help there.

• herbicide. (and I would not comment on this).

Protections are put in place only on the younger trees, where the weights of springs will be too strong.

Personally I use either the lawn mover: much more quicker (often a small old one, just to go under the trees), and a string trimmer. I would use the trimmer on lower speed near trunk, and if I hit strongly, I would really try to be much more softer on the other sides of the trunk. My string trimmer has also the kit for blades, and so a larger protector (that just fit the string). This help me a lot on getting the distances (and I can use it, on the side, as protection, not to get to near to the trunk). Note: shadow and roots help me (on my climate) to get less strong grass near the trunk, so the "precision trimming" is done twice a year.