I have redbuds, serviceberries, dogwoods (florida, alternifolia and kousa) and canadian hemlocks growing under my black walnuts. At ground level, I have trilliums, trout lilies, virginia bluebells as well as daffidols. Japanese maples will also grow under walnuts.

No, you don't have to remove the leaves, because none of these trees or plants are sensitive to the juglone in walnut. The leaves disintegrate fairly rapidly and feed the soil. If you google walnut juglone you should find a number of links which list a much more extensive list of plants which are not sensitive. Some people even grow some plants which are known to be sensitive, such as rhododendrons. Turns out some rhododendrons survive and others don't; similarly, for tulips. The plants I have listed are completely insensitive in that I have never heard of anyone having problems with them and they don't appear on any sensitive lists.
Some people cut down walnuts because of this toxicity. But there really are many, many plants which are not sensitive and also, it takes years for the toxicity to disappear, and walnuts have a fairly open canopy which allows shade tolerant plants to bloom even when right under the canopy -- so I feel you are better off finding out what you can grow. You can also experiment with some plants known to be sensitive, because they usually have to come in contact with the roots and some people do have luck even with juglone-sensitive plants. Just don't try growing tomatoes close by, which I hear always die.

here is a list:

http://ohioline.osu.edu/hyg-fact/1000/1148.html

Thank you for the link and the info. I knew there were some tolerant plants, but for some reason I feel better having a real person tell me they have had success with black walnuts. I'd rather not remove the trees; I'm excited to have them as I've never lived on a property with anything but Norway Maples on it. It'll be so nice to have a garden that's pleasant in the heat of the day..
Michele

Golden Glow is tolerant as is corydalis.

Hi, All,
The walnut tree roots contain tanin. The tanin is reportedly dangerous to all nightshade plants (tomatoes, peppers, potatoes, etc) as well as azalea plants.

My personal experience taught me what tanin can do to potatoes and tomatoes. My peppers did pretty well.
But, the tomatoes would grow well - to a point. Then they'd start wilting, stop thriving, and die off.
All except cherry tomatoes! They can't be stopped!
Potatoes produced a sparse crop. I'm trying them in wire cages this year.

Happy Spring,
Connie

What bugs me about the blacks walnuts around my soggy property is the fallen branches stain my hands if I pick them up wet. I always end up grabbing one, and have to trek back to the house to wash off.

The elderberry bushes I planted last summer by the walnuts seem to be doing ok. They are already trying to start leaves. I will be interested to see how they do.