Creating a Tree Island

One of the primary recommendations when planting a tree is to create a protective area around it, a buffer zone, separating the tree from the lawn. Which is where many people plant a new tree, smack dab in the middle of an existing lawn. Creating that buffer zone keeps out-of-control lawn mowers and weed eaters away from that vulnerable trunk. It is also good not to have the competition of grass, weeds or other dense growth right up to the trunk for other reasons as well including holding moisture against the trunk inviting fungal activity and providing cover for voles to creep in and munch.

This buffer zone is often called a tree island. In a previous blog, The Benefits of a Tree Island, I explain why you would want to create one. This zone not only separates trees and companion plants from turf grass but can also buffer them from other landscape features, such as hardscape.

A beautiful multi-species island at the entrance to the Cleveland Botanical Garden, Cleveland, Ohio

This area can be large but if that doesn’t suit you, it can be a small area. Creating this protective area is relatively easy and using the cardboard method described below precludes the need to use chemical herbicides.

Whereas we like to recommend mulching out to the drip line, if your area is too small to allow that, go with what you can as illustrated in this lovely, but small, back garden.

If this is a fresh planting and you have bare soil, great; you can skip Step One. Otherwise, read on:

Step one – If you have grass or existing weeds, scalp them as close to the ground as possible (without damaging the existing tree trunk). You can use a weed-eater if you stay well away from the tree. It is recommended you first create a buffer by hand-clipping or pulling any unwanted growth to a safe distance away from the trunk. Then scalp the rest of the desired area with whatever implement you have.

Step two – Thoroughly water the soil. Soil should be moist at least 2″ deep…not saturated, but moist.

Step three – Cover the area with a layer of cardboard starting at least a couple of inches away from the trunk. Slightly overlap the seams (if you leave gaps, you will have nice, tidy rows of weeds or grass). Thoroughly water the cardboard. If needed, you can secure the cardboard with landscape staples.

In this picture, we have just started to spread mulch. It will be brushed away from the trunk prior to finishing.

Step four – Top dress with your preferred organic mulch starting at least a couple of inches away from the trunk. Keep the mulch to a very thin layer at that starting point increasing it to a 2″ depth as you get further away from the trunk. You do not want to build up anything near the base of the tree. This is an area which should be allowed to dry out, not kept moist. And notice I said organic mulch. You want the benefits of decomposing matter to go into the soil.

This process will help control weeds for approximately 2 to 3 years in my experience. However, length of efficacy definitely varies depending on climate and the type and density of unwanted growth you are trying to suppress.

The cardboard will decompose in this time and you will have to replace it. However, in my opinion, this beats constant pulling of weeds and/or grass. And the decomposition process benefits the soil, worms and other soil organisms, turning this entire process into a multi-beneficial one.

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