Toxicity & Tolerance

The black walnut tree, juglans nigra, often presents a challenge in the garden as it is allelopathic. This means it releases chemicals from roots and other parts of the tree which harm other plants and organisms. This chemical is called juglone and it can damage certain plants up to 80′ away. It is found in all parts of the plant, so it is very important NOT to use black walnut mulch, leaves, branches or hulls in the garden. Even after a black walnut tree has been removed, the presence of juglone will remain in the soil where the roots were for several years to come. Symptoms of poisoning include chlorosis (yellowing foliage), wilting, deformation, and stunted growth eventually leading to death. There is no cure once plants are infected. Identifying where you or your neighbor(s) have any black walnut trees will help you determine which plants will or will not thrive when planting near.

Tolerant Evergreens

  • Chinese juniper
    Juniperus chinensis
  • Common juniper
    Juniperus communis
  • Eastern red cedar
    Juniperus virginiana
  • Arborvitae
    Thuja sp.
  • Eastern Hemlock
    Tsuga canadensis

Tolerant Vines

  • Clematis
    Clematis sp.
  • Honeysuckle
    Lonicera sp.
  • Virginia Creeper
    Parthenocissus
  • Wild Grape
    Vitis sp.
  • Wisteria
    Wisteria sp.

Tolerant Trees

  • Japanese Maple
    Acer palmatum
  • Red Maple
    Acer rubrum
  • Sugar Maple
    Acer saccharum
  • Serviceberry
    Amelanchier sp.
  • River Birch
    Betula nigra
  • Redbud
    Cercis canadensis
  • Fringe Tree
    Chionanthus sp.
  • Flowering Dogwood
    Cornus florida
  • Hawthorn
    Crataegus sp.
  • Persimmon
    Diospyros virginiana
  • American Beech
    Fagus grandifolia
  • Silverbell
    Halesia carolina
  • Witch Hazel
    Hamamelis sp.
  • Sweet Gum
    Liquidambar styraciflua
  • Tulip Tree
    Liriodendron tulipifera
  • Cucumbertree
    Magnolia acuminata
  • Tupelo
    Nyssa sylvatica
  • Sycamore
    Platanus occidentalis
  • White Oak
    Quercus alba
  • Northern Red Oak
    Quercus rubra
  • Black Locust
    Robinia pseudoacacia
  • Willow
    Salix sp.
  • American Elm
    Ulmus americana

Tolerant Shrubs

  • New Jersey Tea
    Ceanothus americanus
  • Pagoda Dogwood
    Cornus alternifolia
  • Euonymus
    Euonymus sp.
  • Forsythia
    Forsythia sp.
  • Rose-of-Sharon
    Hibiscus syriacus
  • Wild Hydrangea
    Hydrangea arborescens
  • Juniper
    Juniperus sp.
  • Spicebush
    Lindera benzoin
  • Mock-Orange
    Philadelphus sp.
  • Ninebark
    Physocarpus opulifolius
  • Exbury Rhododendron
    Rhododendron hybrids
  • Fragrant Sumac
    Rhus aromatica
  • Currant
    Ribes sp.
  • Black Raspberry
    Rubus occidentalis
  • Elderberry
    Sambucus sp.
  • Maple-leaved Viburnum
    Viburnum acerifolium
  • Korean Spice Viburnum
    Viburnum carlesii
  • Southern Arrowwood Viburnum
    Viburnum dentatum
  • Yucca
    Yucca sp.

Tolerant Perennials, Bulbs, and Wildflowers

  • Yarrow
    Achillea sp.
  • Bugleweed
    Ajuga sp.
  • Hollyhock
    Alcea rosea
  • Windflower
    Anemone sp.
  • Jack-In-The-Pulpit
    Arisaema triphyllum
  • Wild Ginger
    Asarum sp.
  • Aster
    Aster sp.
  • Astilbe
    Astilbe sp.
  • Lady Fern
    Athyrium
  • Bellflower
    Campanula sp.
  • Chrysanthemum
    Chrysanthemum sp.
  • Bleeding Heart
    Dicentra spectabilis
  • Wood Fern
    Dryopteris
  • Purple Coneflower
    Echinacea purpurea
  • Epimedium
    Epimedium sp.
  • Joe Pye Weed
    Eupatorium sp.
  • Snowdrop
    Galanthus nivalis
  • Sweet Woodruff
    Galium odoratum
  • Cranesbill
    Geranium sp.
  • Perennial Sunflower
    Helianthus sp.
  • Hellebore
    Helleborus sp.
  • Daylily
    Hemerocallis sp.
  • Coral Bell
    Heuchera sp.
  • Hosta
    Hosta sp.
  • Siberian Iris
    Iris sibirica
  • Lilyturf
    Liriope sp.
  • Cardinal Flower
    Lobelia sp.
  • Bee Balm
    Monarda sp.
  • Grape Hyacinth
    Muscari sp.
  • Daffodil
    Narcissus sp.
  • Evening Primrose
    Oenothera sp.
  • Cinnamon Fern
    Osmunda cinnamomeum
  • Summer Phlox
    Phlox paniculata
  • False Dragonhead
    Physostegia sp.
  • Jacob’s Ladder
    Polemonium reptans
  • Solomon’s Seal
    Polygonatum sp.
  • Christmas Fern
    Polystichum acrostichoides
  • Primrose
    Primula sp.
  • Lungwort
    Pulmonaria sp.
  • Black-Eyed Susan
    Rudbeckia sp.
  • Siberian Squill
    Scilla sibirica
  • Stonecrop
    Sedum sp.
  • Goldenrod
    Solidago sp.
  • Lamb’s Ear
    Stachys byzantina
  • Spiderwort
    Tradescantia virginiana
  • Trillium
    Trillium sp.
  • Tulip
    Tulipa sp.
  • Speedwell
    Veronica sp.
  • Violet
    Viola sp.

Plants SENSITIVE to Juglone

Juglone – a poisonous chemical released by the Black Walnut Tree

  • alder
  • alfalfa
  • apple
  • asiatic lily
  • asparagus
  • autumn crocus
  • azalea
  • blackberry
  • blueberry
  • cabbage
  • columbine
  • cotoneaster
  • crabapple
  • eggplant
  • forget-me-not
  • hydrangea
  • lilac
  • mountain laurel
  • nicotiana
  • peony
  • pepper
  • petunia
  • pine
  • potato
  • potentilla
  • privet
  • rhododendron
  • rhubarb
  • silver maple
  • spruce
  • tomato
  • viburnum
  • yew