Occasionally, clients will call our offices with complaints that they have an area in their yard where they just can’t seem to grow anything. One of the questions we ask is “Is there a Black Walnut tree nearby?” Black Walnut (Juglans nigra) and a related species, Butternut (Juglans cinerea) produce juglone, a substance that is poisonous to a wide variety of plants. The problem exists in all areas of the soil around these trees.
Black Walnut and Butternut trees are not recommended for use in residential landscapes because of the difficulty in growing other plants nearby. They are best suited to wide-open, natural areas where their beauty and fast growth rate can be appreciated, their nuts can provide food for wildlife, and where they will not interfere with the health of other desirable plants.
The symptoms of juglone poisoning include yellowing or browning of the leaves of affected plants, stunted, twisted growth or a failure to grow, sudden wilting and death. As walnut and butternut trees grow larger and their roots spread, sensitive plants further and further away from the main trunks of these trees will begin to decline in health and may eventually die.
Not all plants are affected by this toxicity problem. Some plants have a natural resistance to juglone and can survive near and even under walnut and butternut trees. Some plants do not grow deep roots, and more shallow root systems seem to be more resistant as well.
Juglone is present in all parts of black walnut and butternut trees. Care needs to be taken when disposing of the nuts, bark and leaves of these types of trees. Do not use these materials for mulch around plants that are not tolerant of juglone.
The following is a list of plants that have been observed growing under black walnut trees. There may be other plants that can be grown in this situation, but the study of this subject is not complete and new additions to the list are discovered from time to time. Even the experts disagree occasionally about whether a plant should be included. This is not scientific research, only observation.
Plants Observed to Grow Under Black Walnut Trees
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TREES
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| Most Maples |
Acer spp. |
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Hawthorn |
Crataegus spp. |
| Pagoda Dogwood |
Cornus alternifolia |
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Honeylocust |
Gleditsia spp. |
| Shagbark Hickory |
Carya ovata |
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Oak |
Quercus spp. |
| Northern Catalpa |
Catalpa speciosa |
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Willow |
Salix spp. |
| Eastern Redbud |
Cercis canadensis |
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Elms |
Ulmus spp. |
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CONIFERS
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| Arborvitae, White Cedar |
Thuja spp. |
| Juniper, Red Cedar |
Juniperus spp. |
| Canadian Hemlock |
Tsuga canadensis |
| SHRUBS |
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| Daphne |
Daphne spp. |
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Most Honeysuckles |
Lonicera spp. |
| Euonymus |
Euonymus spp. |
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Sumac |
Rhus spp. |
| Forsythia |
Forsythia spp. |
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Willow |
Salix spp. |
| Witchhazel |
Hamamelis spp. |
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Most Viburnums |
Viburnum spp. |
| Rose-of-Sharon |
Hibiscus syriacus |
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| PERENNIALS |
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| Hollyhock |
Alcea spp. |
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Shasta Daisy |
Leucanthemum spp. |
| Jack-in-the-Pulpit |
Arisaema triphyllum |
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Virginia Bluebells |
Mertensia virginica |
| Aster |
Aster spp. |
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Bee Balm |
Monarda spp. |
| Astilbe |
Astilbe spp. |
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Phlox |
Phlox spp. |
| Bellflower |
Campanula spp. |
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Solomon’s Seal |
Polygonatum spp. |
| Ferns |
Various species |
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Lungwort |
Pulmonaria spp. |
| Most Grasses |
Various species |
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Rudbeckia |
Rudbeckia spp. |
| Daylily |
Hemerocallis spp. |
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Stonecrop |
Sedum spp. |
| Coral Bells |
Heuchera spp. |
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Goldenrod |
Solidago spp. |
| Many Hostas |
Hosta spp. |
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Lamb’s Ears |
Stachys spp. |
| Siberian Iris |
Iris siberica |
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Spiderwort |
Tradescantia spp. |
| GROUNDCOVERS |
| Bugleweed |
Ajuga reptans |
| Wild Ginger |
Asarum canadense |
| Sweet Woodruff |
Galium odoratum |
| Pachysandra |
Pachysandra terminalis |
| VINES |
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| Clematis |
Clematis spp. |
| Engelmann Ivy |
Parthenocissus tricuspidata |
The following is a list of plants that have been observed to be obviously sensitive to the effects of juglone, and should not be planted under or near black walnut trees.
Plants Observed to be Susceptible to Juglone Toxicity
| TREES |
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| Silver Maple |
Acer saccharinum |
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Apple, Crabapple |
Malus spp. |
| Black Alder |
Alnus glutinosa |
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Basswood, Linden |
Tilia spp. |
| White Birch |
Betula spp. |
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| CONIFERS |
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| Japanese Larch |
Larix kaempferi |
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White Pine |
Pinus strobus |
| Norway Spruce |
Picea abies |
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Scots Pine |
Pinus sylvestris |
| Mugo Pine |
Pinus mugo |
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Yew |
Taxus spp. |
| SHRUBS |
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| Red Chokeberry |
Aronia arbutifolia |
| Cotoneaster |
Cotoneaster spp. |
| Hydrangea |
Hydrangea spp. |
| Lilac |
Syringa spp. |
| Potentilla |
Potentilla spp. |
| Azalea, Rhododendron |
Rhododendron spp. |