I would not recommend it. Raised beds smother a tree's roots which are at the surface and could eventually endanger the tree. My neighbor did this and lived to regret it. Not to mention large trees suck all the moisture away from the plants. Sometimes the tree roots will grow right up into the bed. If this is something you really want, I would dig small holes amongst the roots and plant the plants directly in the ground instead. Amend the pockets of soil and be diligent about watering. Rain will not reach under that canopy and what does will be taken up by the tree. Evergreen groundcovers, hostas, spring bulbs, maybe even some dayliles could work.

I know all about that as we had a silver maple and we put a raised bed around it and the roots grew up into the bed. when we had the tree removed we got rid of the bed but now after planting this tree 7 years ago we really like the look of the raised bed around it but I do remember not many things grew well under it. I did have to water alot.
We have a neighbor that has a red maple right next to our fence and my Knockout rose seems ok there just not as big as my other one's further away. I know Hosta seem to be ok also. Anything else like Black Eyed Susans??

I planted a shade garden under my front maple tree. No raised beds, though. I did as nancyd suggested and placed plants amongst the roots of the tree. This is its 3rd summer and all plants seem to be doing fine and so is the tree. This year we have had a lot of rain so I haven't been watering much, but in previous years it required watering at least once a week during the dry spells that lasted up to two months. I have Japanese painted ferns, Lady In Red Lady ferns, several different hostas, Brunnera, Dolce Key Lime Pie Heuchera, and Bleeding Heart. I mulched as well
Jacquie

Do you have a photo of your bed?? jacquiez?

Black-eyed Susans are pretty tenacious, but they like sun and will do OK if they get enough. Depends on your area and how much sun reaches the plants.

I'm sorry,jess2132000, I don't have any pictures. I don't know how to post pics,yet, so I will have to open a Photo Bucket account and learn. Sorry
Jacquie

Jess....it's not the plants in the raised bed that won't do well....but a raised bed around a tree will eventually kill the tree. May take a few years but unless the tree has a huge root spread and is a huge old tree, it will make the tree deteriorate and eventually die.
Linda C

Agree with the raised bed idea not a very good one. I was told by my nursery that the #1 cause for trees dying is planting them too deep. The roots rot.

I don't have a raised planting bed, and just planted a japanese red maple this year. Beneath I planted Bergenia Bressingham Ruby (shiny leaves turn red in fall), and some Lamium Silver Beacon.

I do plan on supplemental watering for the rest of my life since the tree roots will suck up much of the moisture. LOL

Madagascar Periwinkle does well under my huge maple tree up front, probably because the roots are shallow.