What Not To Grow With Walnut Trees

What Not To Grow With Walnut Trees

For nearly 2,000 years there has been documented evidence of what not to grow with walnut trees. Pliny the Elder, the famous historian wrote “The shadow of the walnut tree is poison to all plants within its compass”. This allelopathic property is a toxin that helps to preserve the walnut tree from competitors.

Back in the 1800s scientists discovered the compound juglone was responsible for killing near by plants. This compound is found in the leaves, branches, fruits, and is also excreted from the roots. Not all plants are bothered by juglone, but those that are will suffer from yellowing leaves, stem wilting, and death.

Which Types Of Walnut Produce Juglone?

Which Types Of Walnut Produce Juglone

All members of the walnut family produce juglone. Including English walnuts, butternut (white) walnuts, pecans, and black walnuts. With black walnuts having the highest concentration of juglone.

Walnut trees contain the chemical hydrojuglone which is non toxic, but when exposed to air or soil it gets oxidized. It then turns into juglone which actually starves plants of oxygen and water. Juglone doesn’t dissolve very well so it stays highly concentrated at the base of the walnut tree.

For many years after the removal of the tree the area will still contain juglone making it impossible to grow certain plants. This is due to the residue roots releasing more of this compound as they decay in the soil.

Of course juglone is not the only reason plants don’t grow within the drip line of walnut trees. Due to the leaf canopy, light restriction is another factor, as is high water uptake from mature trees.

What Not To Grow With Walnut Trees

What Not To Grow With Walnut Trees

There are many plants that can be successfully grown with walnuts, but there are some exceptions to this and the following will not grow with walnuts.

Vegetables That Do NOT Grow Well With Walnuts

  • Asparagus
  • Brassicas (members of the cabbage family)
  • Peppers
  • Chillis
  • Tomatoes
  • Aubergines (egg plants)
  • Potatoes
  • Alfalfa
  • Rhubarb

Trees That Do NOT Grow Well With Walnuts

  • Apples
  • Pears
  • Spruce
  • Birch
  • Alder

Plants That Will Grow Near Walnut Trees

Plants That Will Grow Near Walnut Trees

There are quite a few plants that will grow happily near walnut trees as long as they recieve enough light and water. These include:-

Vegetables That WILL Grow With Walnut Trees

  • Onions
  • Beetroot
  • Squash
  • Melons
  • Carrots
  • Parsnips
  • Beans
  • Jerusalem artichoke
  • Sweet corn

Many trees are also juglone tolerant including Maples, Poplar, White ash, Elm and many more.

Fruit Trees That WILL Grow With Walnut Trees

  • Persimmon
  • Quince
  • Peach
  • Nectarine
  • Pawpaw
  • Plum
  • Cherry

You can also grow wild grape vines (vitis) near walnuts. As with all things this is about trial and error. There are many factors that contribute to healthy plant growth.

But by abiding to the lists above you should be able to companion plant this notorious bad neighbour.

Leave a Reply

Your email address will not be published. Required fields are marked *