Is This A Mistake? 85 Plants for Gardening Under Black Walnut Trees.

These are some of the plants that have been reported as growing under black walnut trees.

Note that while some of these might live, they might not thrive or grow as well as they would outside of the influence of the walnut.

It turns out much of this might be wrong.

There’s a growing conversation on the Net suggesting the entire notion that Black Walnuts kill plants by secreting Juglone isn’t correct.

Hormone Secretion

For the record, the reason that plants do not grow well under black walnut trees is the roots of the tree secrete a hormone “juglone”.
The effect of the hormone will be felt by plants in the root zone of the tree.

The root zone of the tree extends for a distance of twice the distance from the trunk to the drip line.

So, in other words, if the distance from the trunk to the drip line (where the tree branches “end”) is 20 feet. The roots will extend approximately another twenty feet from the drip line.

The effective area the tree roots will then secrete juglone is forty feet from the trunk. If the distance from the trunk to the drip line is 15 feet, then the secretion area is 30 feet from the trunk.

Hormone Breaks Down

This hormone is broken down by composting.

When juglone is exposed to air, water and composting bacteria the toxic effect breaks down in two to four weeks. If you’re not sure, try planting a tomato transplant in the compost.

f juglone is present, the transplant will die within a few weeks.

Sawdust or chippings from the tree should not be used fresh around plants. It takes approximately six months for the juglone to disappear from wood chips and sawdust.

Applying fresh black walnut chips would be like to trying to grow under black walnut trees.

Plant List For Success Under Black Walnut Trees

Trees
• Japanese Maples, Acer palmatum and its cultivars
• Southern Catalpa, Catalpa bignonioides
• Eastern Redbud, Cercis canadensis
• Canadian Hemlock, Tsuga canadensis

Vines and Shrubs
• Clematis ‘Red Cardinal’
• February Daphne, Daphne mezereum
• Euonymus species
• Weeping Forsythia, Forsythia suspensa
• Rose of Sharon, Hibiscus syriacus
• Tartarian Honeysuckle, Lonicera tatarica, and most other Lonicera species
• Virginia Creeper, Parthenocissus quinquefolia
•Rhododendron periclymenoides ‘Gibraltar’ and ‘Balzac’

•Rhododendron Exbury hybrids
• Multiflora Rose, Rosa multiflora
• Black Raspberry, Rubus occidentalis
• Arborvitaes, Thuja species
• Koreanspice Viburnum, Viburnum carlesii, and most other Viburnum species

Annuals
• Pot-marigold, Calendula officinalis ‘Nonstop’
• Begonia, fibrous cultivars
• Morning Glory, Ipomoea ‘Heavenly Blue’
• Pansy Viola
• Zinnia species

Vegetables
• Squashes
• Melons
• Beans
• Carrots
• Corn

Fruit Trees
• Peach
• Nectarine
• Cherry
• Plum
• Pear-Pyrus species

Herbaceous Perennials  (you can read about other perennial flowers here)

• Bugleweed, Ajuga reptans
• Hollyhock, Alcea rosea
• American Wood Anemone, Anemone quinquefolia
• Jack-in-the-Pulpit, Arisaema triphyllum
• European Wild Ginger, Asarum europaeum
• Astilbe species
• Bellflower, Campanula latifolia
• Chrysanthemum species (some)
• Glory-of-the-Snow, Chionodoxa luciliae
• Spring Beauty, Claytonia virginica
• Crocus species
• Dutchman’s Breeches, Dicentra cucullaria
• Leopard’s-Bane, Doronicum species
• Crested Wood Fern, Dryopteris cristata
• Winter Aconite, Eranthis hyemalis
• Snowdrop, Galanthus nivalis
• Sweet Woodruff, Galium odoratum
• Herb Robert, Geranium robertianum
• Cranesbill, Geranium sanguineum
• Grasses (most) Gramineae family
• Jerusalem Artichoke, Helianthus tuberosus
• Common Daylily, Hemerocallis ‘Pluie de Feu’
• Coral Bells, Heuchera x brizoides
• Orange Hawkweed, Hieracium aurantiacum
• Plantain-lily, Hosta fortunei ‘Glauca’
• Hosta lancifolia
• Hosta marginata
• Hosta undulata ‘Variegata’
• Siberian Iris, Iris sibirica
• Balm, Monarda didyma
• Wild Bergamot, M. fistulosa
• Grape Hyacinth, Muscari botryoides
• Sweet Cicely, Myrrhis odorata
• Sundrops, Oenothera fruticosa
• Senstitive Fern, Onoclea sensibilis
• Cinnamon Fern, Osmunda cinnamomea
• Peony, Paeonia species (some)
• Summer Phlox, Phlox paniculata
• Mayapple, Podophyllum peltatum
• Jacob’s-Ladder, Polemonium reptans
• Great Solomon’s-Seal, Polygonatum commutatum
• Polyanthus Primrose, Primula x polyantha
• Lungwort, Pulmonaria species
• Bloodroot, Sanguinaria canadensis
• Goldmoss Stonecrop, Sedum acre
• Showy Sedum, Sedum spectabile
• Lamb’s-Ear, Stachys byzantina

• Nodding Trillium, Trillium cernuum
• White Wake-Robin, Trillium grandiflorum
• Tulipa Darwin ‘White Valcano’ and ‘Cum Laude,’ Parrot ‘Blue Parrot,’ Greigii ‘Toronto’
• Canada Violet, Viola canadensis
• Horned Violet, Viola cornuta
• Woolly Blue Violet, Viola sororia

Plant List To Avoid (Extreme Sensitivity) For Under Black Walnuts

These may not grow well even well outside the normal range. (triple the distance from trunk to drip line)

Herbaceous Perennials
• Colorado Columbine, Aquilegia caerulea
• Wild Columbine, Aquilegia canadensis
• Asparagus, Asparagus offinalis
• Chrysanthemum Chrysanthumum species (some)
• Baptisia australis
• Hydrangea species
• Lilies, Lilium species (particularly the Asian hybrids)
• Narcissus ‘John Evelyn,’ ‘Unsurpassable’ ‘King Alfred’ and ‘Ice Follies’
• Peonies, Paeonia species (some)
• Rhubarb, Rheum rhabarbarum

Trees
• Silver Maple, Acer saccharinum
• European Alder, Alnus glutinosa
• White Birches, Betula species
• Northern Hackberry, Celtis occidentalis
• Apples and Crabapples, Malus species
• Norway Spruce, Picea abies
• Mugo Pine, Pinus mugo
• Red Pine, Pinus resinosa
• Eastern White Pine, Pinus strobus
• Basswood, Tilia heterophylla

Shrubs
• Red Chokeberry, Aronia arbutifolia
• Hydrangea species
• Mountain Laurels, Kalmia species
• Privet, Ligustrum species
• Amur Honeysuckle, Lonicera maackii
• Brush Cinquefoil, Potentilla species
• Rhododendrons and Azaleas,
• Blackberry, Rubus allegheniensis
• Lilacs, Syringa species and cultivars
• Yew, Taxus species
• Blueberry, Vaccinium corymbosum
• Viburnum plicatum tomentosum ‘Mariesii’

Annuals and Vegetables Transplants
• Cabbage, Brassica oleracea capitata
• Peppers, Capsicum species (some)
• Tomatoes, Lycopersicon esculentum
• Flowering Tobacco, Nicotiana alata
• Petunia species and cultivars
• Eggplant, Solanum melongena
• Potato, Solanum tuberosum

I hope this list helps you grow your garden under black walnut trees.
It has been compiled from multiple sources and there may be some disagreement between them.