Beware the Black Walnut!

The wolf in sheep's clothing, or rather, the nut in a lime citrus fruit's husk; Juglans nigra; and most commonly known as the Black Walnut.

A beautiful, rapidly growing nut tree with BIG nuts! (and did I mention hard ones to open!)  Their leaves and the nuts look almost tropical with their breezy palm nature. 

However, Black Walnuts do not get along with some other plants.  All parts of their body (roots, nuts, leaves) secrete a chemical called juglone that can be toxic to other plants, causing them to wilt, stunt growth, yellow leaves, and eventual death.  As you can see above, this is such the case with the Gooseberry bush I unknowingly planted right underneath the Black Walnut (because gooseberries can handle shade!  But NOT the shade of a black walnut!).  Here is a list as found on Morton Aboretum's website of plants that are sensitive to Black Walnut's juglone:

PLANTS SENSITIVE TO BLACK WALNUT TOXICITY

Annuals and vegetables: asparagus, cabbage, eggplant, flowering tobacco, pepper, petunia, potato, tomato

Herbaceous perennials: autumn crocus, baptisia, columbine, lily (Asian hybrids), peony, rhubarb

Shrubs: blueberry, red chokeberry, cotoneaster, Amur honeysuckle, hydrangea, lilac, privet, potentilla, rhododendron, yew, and some viburnum shrub species

Trees: European alder, white birch, crabapple species, hackberry, larch, linden, saucer magnolia, mugo pine, red pine, white pine, Norway spruce, silver maple, and some viburnum tree species

Luckily, Black Walnut DOES get along with other plants.  Many of them!  Check it out- if you're on this list, you've got a friendship in store:

PLANTS TOLERANT OF BLACK WALNUT TOXICITY

TREES
Box Elder	Acer negundo		Silverbell	Halesia tetraptera
Japanese Maple	Acer palmatum & cvs.		Witchhazel	Hamamelis spp.
Red Maple	Acer rubrum		Sweetgum	Liquidambar styraciflua
Sugar Maple	Acer saccharum		Tuliptree	Liriodendron tulipifera
Ohio Buckeye	Aesculus glabra		Cucumber Tree	Magnolia acuminata
Sweet Buckeye	Aesculus octandra		Mulberry	Morus spp.
Tree of Heaven	Ailanthus altissima		Blackgum	Nyssa sylvatica
Serviceberry	Amelanchier spp.		Sycamore	Platanus occidentalis
Pawpaw	Asimina triloba		American Plum	Prunus americana
Sweet Birch	Betula lenta		Pin Cherry	Prunus pensylvanica
Yellow Birch	Betula lutea		Wild Black Cherry	Prunus serotina
River Birch	Betula nigra		White Oak	Quercus alba
American Hornbeam	Carpinus caroliniana		Scarlet Oak	Quercus coccinea
Hickory	Carya spp.		Shingle Oak	Quercus imbricaria
Chestnut	Castanea dentata		Red Oak	Quercus rubra
Catalpa	Catalpa bignonioides Catalpa speciosa		Black Oak	Quercus velutina
Redbud	Cercis canadensis		Staghorn Sumac	Rhus typhina
			Black Locust	Robinia pseudoacacia
Hawthorn	Crataegus spp.		Willow	Salix spp.
Persimmon	Diospyros virginiana		Sassafras	Sassafras albidum
Beech	Fagus grandifolia		American Elm	Ulmus americana
White Ash	Fraxinus americana		Slippery Elm	Ulmus rubra
Black Ash	Fraxinus nigra
Honeylocust (and thornless Honeylocust)	Gleditsia triacanthos andGleditsia triacanthos f.inermis
EVERGREENS
Chinese Juniper	Juniperus chinensis		Arborvitae	Thuja spp.
Common Juniper	Juniperus communis		Eastern Hemlock	Tsuga canadensis
Red Cedar	Juniperus virginiana
VINES
Dutchman's Pipe	Aristolochia durior		Virginia Creeper	Parthenocissus spp.
Bittersweet	Celastrus spp.		Greenbriar	Smilax spp.
Clematis	Clematis ssp.		Wild Grape	Vitis spp.
Honeysuckle Vine	Lonicera spp.
SHRUBS
Speckled Alder	Alnus rugosa		Exbury Rhododendron	Rhododendron hybrids
Hercules-club	Aralia spinosa		Fragrant Sumac	Rhus aromatica
Spicebush	Lindera benzoin		Shining Sumac	Rhus copallina
New Jersey Tea	Ceanothus americanus		Smooth Sumac	Rhus glabra
Fringe Tree	Chionanthus virginicus		Currant	Ribes spp.
Pagoda Dogwood	Cornus alternifolia		Wild Rose	Rosa spp.
Silky Dogwood	Cornus amomum		Black Raspberry	Rubus occidentalis
American Hazelnut	Corylus americana		Purple Raspberry	Rubus odoratus
February Daphne	Daphne mezereum		Elderberry	Sambucus spp.
Euonymus	Euonymus spp.		Bladdernut	Staphylea trifolia
Forsythia	Forsythia spp.		Mapleleaf Viburnum	Viburnum acerfolium
Rose of Sharon	Hibiscus syriacus		Fragrant Viburnum	Viburnum carlesii & cvs.
Shrubby St. Johnwort	Hypericum prolificum		Arrowwood	Viburnum dentatum
Beautybush	Kolkwitzia amabilis		Blackhaw	Viburnum prunifolium
Honeysuckle (most)	Lonicera spp.		Adam's Needle	Yucca spp.
Ninebark	Physocarpus opulifolius		Prickly Ash	Zanthoxylum americanum
HERBACEOUS PERENNIALS, SPRING WILDFLOWERS AND BULBS
Bugleweed	Ajuga spp.		Perennial Sunflower	Helianthus spp.
Hollyhock	Alcea rosea		Daylily	Hemerocallis spp.
Windflower	Anemone spp.		Coral Bell	Heuchera spp.
Jack-in-the-Pulpit	Arisaema triphllyum		Hosta	Hosta spp.
Wild Ginger	Asarum spp.		Siberian Iris	Iris sibirica
Aster	Aster spp.		Bush Clover	Lespedeza spp.
Astilbe	Astilbe spp.		Lobelia	Lobelia spp.
Lady Fern	Athyrium spp.		Peppermint	Mentha piperita
Rattlesnake Fern	Botrychium spp.		Bee Balm	Monarda spp.
Bellflower	Campanula spp.		Grape Hyacinth	Muscari spp.
Chrysanthemum	Chrysanthemum spp.		Daffodil selected	Narcissus spp.
Spring Beauty	Claytonia spp.		Evening Primrose	Oenothera spp.
Fragile Fern	Cystopteris fragilis		Sensitive Fern	Onoclea sensibilis
Toothwort	Dentaria spp.		Cinnamon Fern	Osmunda cinnamomea
Bleeding Heart	Dicentra spectabilis		Summer Phlox	Phlox paniculata
Leopard's Bane	Doronicum spp.		False Dragonhead	Physostegia spp.
Wood Fern	Dryopteris spp.		May Apple	Podophyllum peltatum
Winter Aconite	Eranthis hyemalis		Jacob's Ladder	Polemonium reptans
Joe-pyeweed	Eupatorium spp.		Solomon's Seal	Polygonatum spp.
Sweet Woodruff	Galium odoratum		Christmas Fern	Polystichum spp.
Cranesbill	Geranium spp.		Primrose	Primula spp.
Lungwort .	Pulmonaria spp		Spiderwort	Tradescantia virginiana
Buttercup	Ranunculus spp.		Trillium	Trillium spp.
Black-eyed Susan	Rudbeckia spp.		Tulip	selected Tulipa spp.
Bloodroot	Sanguinaria canadensis		Bellwort	Uvularia spp.
Stonecrop	Sedum spp.		Speedwell	Veronica spp.
Goldenrod	Solidago spp.		Violet	Viola spp.
Lamb's Ears	Stachys byzantina

References: The Morton Arboretum website, 

http://www.mortonarb.org/tree-plant-advice/article/887/plants-tolerant-of-black-walnut-toxicity.html