Too much mulch smothers a tree's roots, a little is OK. Mulch piled up around a tree's trunk can be a vector for diseases that might get into the tree. Some plants can compete with a tree's roots for water and nutrients. It's a tricky proposition. That said, it can be done. Also, easiest to do and least disturbance for the tree is perennials, but a lot of them look great only for a short part of the season. So, then folks plant a mix so that some things bloom when others are through. That can get to be tricky too, planning it all out keeping the tree's health in mind. That said, it can be done. Some plants can actually be good companions to an apple tree. I don't know any for sure, but some I've heard about as general comapnion plants are rue, chives, chamomile and yarrow. Tansy is supposed to be good for apples but I'm not a fan of that plant, it gets big and leggy. Others in this vein are marigolds and nasturtiums. In the line of "keep it simple" might I suggest a ground coverish plant called sweet woodruff. It has cute white flowers in the spring and attractive foliage most of the rest of the time. It's not horribly invasive. You can even dry the leaves and they smell like vanilla. In the olden days folks used to float this plant in wine punch to flavor it and make "May wine." Below is a cute picture I found online of a birch tree underplanted with sweet woodruff and a few other things. Don't overdo it or you're back to square one as I mention above. Google sweet woodruff and you'll find out a lot about it. Some little spring bulbs might be nice that would later get hidden by the groundcover when they fade out. Here is a link that might be useful: Sweet woodruff and forget-me-nots

Lady's Mantle that doesn't spread? I need some of that! You'll have enough excess plants to try again under the crabapple if you choose to later on.

I'm having the same burning out problem with Fire and Ice and also Hawkeye. I remember using Buggetta slug control a few weeks ago and as I came to the bottom of the box, I dispersed the "crumbs" willy nilly over some Hosta. Country Garden mentioned chemical burn, and I'm assuming that is what is wrong with my leaf damage. I don't even want to think about nematodes!! Mary

You might want to try corn gluten, which inhibits growth of seedlings. It is also a mild fertilizer.