On the left is a 30 year old Cedar of Lebanon with ice plant below; right front, a small oak tree and festuca grass with lava rocks and dirt, and right back, there is a cottonwood tree with dogwoods behind it and some shrubs (I forget what they were, and I cannot tell from the picture) with more lava rocks and dirt. Hidden under the cedar are some aloe plants.
After skirting the tree, we put in irrigation. Robert brought in a couple of yards of topsoil and compost and rototilled that in to the soil under the tree. The cedar tree does not seem to have suffered for having its top layer of roots damaged. It is healthy and growing at a rather alarming rate.
The next step is the plant selection. The cedar tree complicates the issue in that it provides quite a bit of shade, and I wanted a garden that looked like a cottage garden. Cottage gardens are traditionally sun gardens. In addition, the tree sucks up alot of the moisture in the soil, and it drops a 2 inch (5 cm) layer of needles every year.
Those conditions and my requirement of riotous color made plant selection very important. They had to be plants that like hot, dry shade and acid conditions. Most plants prefer a slightly acid soil, so that was less of a problem than I feared. And because of our skirting the tree, I was able to ignore that shade restriction around the edge of the garden. Soon, I will have a plant list, but along with cyclamen, fushias, and ferns, I have roses and bearded iris growing under that tree. I was willing to experiment and try plants, like the bearded iris, that books said were not suited for that environment.
Finally, I pick up needles every week. Clean-up is just as important as the previous steps because even the most appropriate plant cannot survive under a suffocating layer of needles. It is hard work, and it is a lot of work. I do not clean up the entire garden every week.
It is possible to have a glorious garden under a tree that produces dense shade, takes up the moisture in the soil, and drops a lot of stuff, but it is a big commitment. You will probably have to do the following:
Plants that have done well under the cedar tree.