Shop Products
Houzz Logo Print
chundered

Azaleas and black walnuts

chundered
16 years ago

I've been searching the net and find conflicting info on black walnuts and azaleas. I recently built a rasied bed under one of my black walnuts and want to put a couple of azaleas in it. The bed is not very deep, about 4 inches. Are the azaleas going to survive if I do put them in? I've seen some posts on the web indicating that azaleas won't like it but a few others saying they have azaleas doing fine under a black walnut.

Comments (2)

  • morz8 - Washington Coast
    16 years ago

    It seems there are a couple of specific azaleas that will grow under black walnut, but for the most part you aren't going to be able to grow rhododendron or azaleas directly under the tree.

    UW Plant Pathology - "The toxic effects of a mature black walnut tree can extend 50 to 80 feet from the trunk of the tree, with the greatest toxicity occurring within the treeÂs dripline. In this area, plants susceptible to juglone may wilt or die; plants tolerant to juglone will grow normally. Vegetables such as tomato, potato, eggplant and pepper, and ornamentals such as lilac, peony, rhododendron and azalea are particularly sensitive to juglone."

    Here is a link that might be useful: Last Falls Black Walnut thread - note Exburys

  • rhodyman
    16 years ago

    The roots of Black Walnut (Juglans nigra L.) and Butternut (Juglans cinerea L.) produce a substance known as juglone (5-hydroxy-alphanapthaquinone). Persian (English or Carpathian) walnut trees are sometimes grafted onto black walnut rootstocks. Many plants such as tomato, potato, blackberry, blueberry, azalea, mountain laurel, rhododendron, red pine and apple may be injured or killed within one to two months of growth within the root zone of these trees. The toxic zone from a mature tree occurs on average in a 50 to 60 foot radius from the trunk, but can be up to 80 feet. The area affected extends outward each year as a tree enlarges. Young trees two to eight feet high can have a root diameter twice the height of the top of the tree, with susceptible plants dead within the root zone and dying at the margins. The juglone toxin occurs in the leaves, bark and wood of walnut, but these contain lower concentrations than in the roots. Juglone is poorly soluble in water and does not move very far in the soil. [From Ohio State University Extension Fact Sheet HYG-1148-93 by Richard C. Funt and Jane Martin]

    The Ohio State University Extension and the American Horticultural Society have reported that R. periclymenoides, formerly R. nudiflorum, Pinxterbloom Azalea, and Exbury Azaleas Gibraltar and Balzac will grow near Black Walnut and Butternut trees.

    If you want to grow azaleas under walnut trees, use a raised bed with landscape cloth underneath to keep the walnut roots out, and remove the fallen leaves each year.

Sponsored
Hoppy Design & Build
Average rating: 5 out of 5 stars9 Reviews
Northern VA Award-Winning Deck ,Patio, & Landscape Design Build Firm