I’m planning to replace the lawn in my front yard with a groundcover. There is a gingko tree planted by the city in the middle of the yard. If I don’t want to disturb the roots of the tree, how deep and how close to the tree should I (or should I not) dig the lawn out?
This remarkable tree is known as a ‘living fossil’, as it is the sole survivor of an ancient group of trees that date back to beyond the time of the dinosaurs. You have not told us how old or how large your tree is, so it is hard to know exactly where the root structure is at in terms of establishing it’s root system. According to an article in Fine Gardening Magazine though, “Some trees are more agreeable than others about giving up some of their ground.” It appears that the Gingko tree will happily tolerate disturbance around it’s roots. https://www.finegardening.com/how-to/articles/planting-under-a-tree.aspx
The Gingko is a very slow going tree and it tends to root more deeply than others, particularly if it has been given sufficient irrigation in its lifetime. There isn’t a specific rule of thumb though for how far down you can go. If there are roots from your tree near the surface, you should avoid damaging any root that is more than an inch or two thick. Your best practice may be to hand dig to ensure that you can see the root structure as you excavate for your new planting. Using a small hand trowel, dig holes big enough to accommodate the roots of your under-planting materials. If you encounter a large root, move your planting hole to avoid the root. Cutting through smaller roots does the tree no real harm. New roots will grow from the point at which the old root was severed. Put a sprinkling of slow-release fertilizer in the hole, following package instructions. Tuck them into the holes, firming soil around the roots so as to avoid air pockets. It’s best to work in sections starting near the tree trunk and working away to the planting bed perimeter, lightly watering sections as you go. This will minimize compaction of the soil and keep things moist without being muddy. The University of Minnesota has written an excellent article on planting under trees. https://www.sustland.umn.edu/implement/planting.html
Good luck with your project.