Juglone, a substance produced in the roots and leaves of black walnut trees, is toxic to some plants. If there are any remnants of roots left, you may see signs of juglone toxicity for a few years, until these roots decompose completely. To be safe, you may want to consider growing plants that have shown resistance to juglone toxicity. Most annuals thrive where a black walnut once stood, as do these plants: Bulbs. Crocus, daffodils, tulips Perennials. Astilbe, bleeding heart (Dicentra), columbine (Aqilegia), coral bells (Heuchera), daylily (Hemerocallis), perennial geranium, spiderwort (Tradescantia), yarrow (Achillea) Shrubs. Japanese maple (Acer palmatum), Rose of Sharon (Hibiscus syriacus), Spirea.