Question
I have been wanting to buy Saucer Magnolia Tree for my yard and I wondered about my Neighbor's  3 Walnuts Tree that are lined up on my side of the yard and if The Saucer Magnolia tree will strive close by the Walnuts trees? I hear that Walnuts Tree emits some thing toxic and causes some plants not to strive..is that right ? does that mean I cannot have Saucer Magnolia tree???

Answer
This tree needs to be in full sunlight. Walnut trees secrete a chemical called juglone. Plants adversely affected by being grown near black walnut trees exhibit symptoms such as foliar yellowing, wilting, and eventual death. The causal agent is a chemical called "juglone" (5 hydroxy-1, 4-napthoquinone), which occurs naturally in all parts of the black walnut. It is a way to keep down competition from other plant with the walnut plants. This distribution of juglone means that some sensitive plants may tolerate the amount of juglone present in the soil near a black walnut tree, but may not survive directly under its canopy. Alternatively, highly sensitive plants may not tolerate even the small concentration of juglone beyond the canopy spread. Species survival near or under black walnut trees is further complicated by the fact that the amount of juglone present in the soil depends on soil type, drainage, and soil micro-organisms. Competition for light and moisture under the canopy also greatly affects which species survive where.

Plantings should be located away from black walnut trees to prevent damage to susceptible plants. If proximity to such trees is unavoidable, then raised beds afford a means of protection. However, the bed must be constructed in such a way as to minimize tree root penetration into the raised portion. Care must then be taken to keep the beds free of black walnut leaf litter or nuts.

Saucer magnolia is one of the sensitive plants to walnut. Plant the tree as far away from the walnut from the walnut as possible and you will not have a problem.