"brooklyn1" wrote in
:

You've got it back asswards; not much grows under walnut, they
poison the soil.

actually, native trees & shrubs tend not to have any problems
growing under the dripline or in the root zone of black walnuts. the
non-native plantings many people put in for landscaping are stunted
or killed by the juglone.
for example, there was an apple tree that started dying when the
largest black walnut in my yard started growing over it, so i just
cut it down. apples are non-native (with the exception of a couple
crabapple species). there is a native dogwood growing direct under
the walnut & about 2' away from the trunk, that is thriving.
unfortunately, the grass grows just fine there too...

The OP already indicated that his yard is rather small so any
discussion about his growing walnut is rather moot... walnut
trees grow huge... his choices are to grow a smaller tree or get
a larger yard.

that's a silly statement. you can grow several walnuts in a 50'x50'
back yard. you just won't be able to grow non-native understory
plantings too.
lee