Mine is lawn, but there are a lot of trees and shrubs that are part of large mulched areas. The original plan for the mulched areas was to reduce mowing; however, it's been rough getting things to establish because of the clay soil. Part of that is because it takes about 150 ft of hose to get water to some areas (file this under 'too lazy to reel it in and out on hot days and don't want to pump the well dry'). Those hot and dry spells in the summer can make it tough to keep the soil moist. I usually wait until there is an obvious sign that things need water, but with some of those plants, the time between first signs and death is very short. But I do plant a few vegetables in those areas. Making a nice place for earthworms is definitely on my mind. In the places where I see worms, there is a noticeable difference in the soil. It's just that the organic material is only present in the first inch or two of ground. It is getting deeper over time, but this area was a poorly managed farm until is was no longer producing much at all. It's come a long way since then, but I'm getting older and a bit impatient.