Plants - Trees and Shrubs

What will grow under a black walnut?

Discover what will survive under this toxic tree


Though beautiful, black walnut trees (Juglans nigra) can be a challenge for gardeners: their roots, leaves, husks and buds produce juglone, a respiratory inhibitor in some plants and animals. (“Allelopathy” is when the toxicity from one plant inhibits the growth of another.) The poisonous zone extends about 20 to 30 metres from the trunk of a mature tree, far beyond its canopy.

To reduce the amount of juglone released, regularly clean up tree debris, especially fallen leaves and fruit (but do not compost it). Also, try to maintain high organic levels in the soil by using lots of compost, leaf mould and manure, which will encourage beneficial soil microbes that neutralize toxins. Here’s a list of plants that are juglone tolerant and worth trying to grow under your black walnut: 

  • Japanese maple (Acer palmatum) Zone 6
  • 
Bugleweed (Ajuga reptans) Zone 4
  • European wild ginger (Asarum europaeum) Zone 5
  • Eastern redbud (Cercis canadensis) Zone 5
  • Winged euonymus (Euonymus alatus) Zone 3
  • Golden bells (Forsythia suspensa) Zone 5
  • Narrow-leafed plantain lily (Hosta lancifolia) Zone 3
  • Cinnamon fern (Osmunda cinnamomea) Zone 3
  • Virginia creeper (Parthenocissus quinquefolia) Zone 4
  • Kentucky bluegrass 
(Poa pratensis) Zone 3
  • Great Solomon’s seal (Polygonatum biflorum var. commutatum) Zone 3
  • Lungwort (Pulmonaria spp.) Zone 3
  • Arborvitae (Thuja spp.) Zone 2
  • Canadian hemlock (Tsuga canadensis) Zone 3


For additional information, check out the Ministry of Agriculture, Food and Rural Affairs’ website.








Photo courtesy of Quadell

 

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