I have many Calycanthus' and Illiciums, some of which are variegated, some of which are known as Carolina Anise.. I don't pay attention to the tags so I don't know which ones are named varieties. Most were given to me over the years and are un-named. They all do well in the oak root zone but I have to mound up good soil on top of a small square of landscape fabric laid across the ground. Every couple of years I have to mound up more soil but by then I am needing to get in there and chop out baby plants anyway.

You might consider Fatsia. I can only grow it in a pot since the voles love it as much as I do.

You also might consider standard hanging basket houseplants which will creep across the ground and cover up to four feet square by fall. They are easy to keep watered as long as you can see the pot. Swedish Ivy (not a true ivy nor is it from Sweden) and Wandering Jew (not lost nor is it religious) work wonders in my tree filled yard. If you half sink the pot in the ground you won't have to water as much, the roots extend out past the plastic.

See the posting about Plant Delights Open House, towards the end we talk about a Wandering Jew relative named Baby Bunny Bellies that is hardy and an aggressive grower.

Thought I was the only one who lost multiple fatsias to voles, John - I surround mine with wire cages now as I plant them! I've got a similar situation (trees and unplantable space beneath), and I use wooden half barrels containing deciduous azaleas underplanted with trilliums, cyclamen, epimediums, etc. Cyclamen coum in full bloom right now are beautiful, and this affords them and the azaleas the drainage they need to do well. Some of the barrels are decaying (one is almost non-existent), but the rootball of the azalea actually seems to enjoy sitting "high and dry", and I fill in between the planters every fall with leaves, etc. I'm also experimenting with Hellebores in "grow bags" - permeable 3-5 gallon bags filled with potting medium that drain and breathe better than regular pots (Hellebores are very difficult to maintain in plastic pots for extended periods, but I've had plants in these for 3 years now, and they seem to be doing well.) These can be sandwiched in between the larger planters and camouflaged with mulch or leaves so that the entire planting, though modular, looks natural. No reason it wouldn't work with annuals, either, but they'd need more water in the summer.

Thanks for the ideas. The hanging baskets as groundcover and the bottomless pots and grow bags are great ideas. I like to experiment and have a little fun with it. I might even be able to keep an azalea alive! Now that would be something...

The breathable bag idea should work well for Daphne odora also, or just use a large pot and rarely water it. Mine have been blooming for over a month and they are one of those plants that makes you wish there was a law that required it to be grown here since it does so well and smells so nice.