[trisham]

I haven’t found any problems with cedar trees, but black walnuts can be difficult:

Potential Problems - Aside from leaf spot, Black Walnut is virtually disease and pest free. However, it is famous for the production by its roots of juglone, a chemical that is toxic to some nearby competitor plants. In a woodland setting, very few plants grow under the canopy of this species. When summer drought occurs, the response of this tree is to begin dropping leaves, in spite of its deep taproot system. In an urban setting, a constant rain of leaflets, rachises, dead twigs, stain-laden whole fruits, and debris from squirrel feeding occurs from mid-summer until late autumn, presenting a constant clean-up chore and mowing hazard.

and

PLANTS SENSITIVE TO BLACK WALNUT TOXICITY

Annuals and vegetables: asparagus, cabbage, eggplant, flowering tobacco, pepper, petunia, potato, tomato

Herbaceous perennials: autumn crocus, baptisia, columbine, lily (Asian hybrids), peony, rhubarb

Shrubs: blueberry, red chokeberry, cotoneaster, Amur honeysuckle, hydrangea, lilac, privet, potentilla, rhododendron, yew, and some viburnum shrub species

Trees: European alder, white birch, crabapple species, hackberry, larch, linden, saucer magnolia, mugo pine, red pine, white pine, Norway spruce, silver maple, and some viburnum tree species

[greeneyes]

Yep. Several of my raised beds are right next to the tree. I use those for winter wheat, winter rye, strawberries and I got one year of great melons, before the soil borne disease set in - haven’t been able to grow a decent melon since then.