Alterative; Anodyne; Antiinflammatory; Astringent; Blood purifier; Blood
tonic; Detergent; Emetic; Laxative; Pectoral; Vermifuge.
- Alterative = Tending to restore to normal health
- Anodyne = Capable of soothing or eliminating pain
- Antiinflammatory = Preventing or reducing inflammation.
- Astringent = Tending to draw together or constrict tissues;
- Blood purifier = agent that rids blood of impurities; cleanse.
- Blood tonic = invigorating, refreshing and restoring
- Detergent = A cleansing substance that acts similarly to soap
- Emetic = Causing vomiting.
- Laxative = stimulates evacuation of the bowels
- Pectoral = Useful in relieving disorders of the chest or
- Vermifuge = Anthelmintic =
expelling or destroying parasitic worms especially of the intestine
Black walnut is toxic for horses!
The juice from the fruit husk is applied externally as a treatment for
ringworm[222, 257]. The husk is chewed in the treatment of colic and applied as
a poultice to inflammations.
The bark and leaves are alterative, anodyne, astringent, blood tonic,
detergent, emetic, laxative, pectoral and vermifuge[4, 222, 257]. Especially
useful in the treatment of skin diseases, black walnut is of the highest value
in curing scrofulous diseases, herpes, eczema etc. An infusion of the bark is
used to treat diarrhoea and also to stop the production of milk, though a strong
infusion can be emetic[21, 257]. The bark is chewed to allay the pain of
toothache and it is also used as a poultice to reduce the pain of headaches[222,
A tea made from the leaves is astringent. An infusion has been used to
lower high blood pressure. It can be used as a cleansing wash. The
pulverized leaves have been rubbed on the affected parts of the body to destroy
The sap has been used to treat inflammations.
|Common name: Black walnut
||Europe, Eastern N. America - Massachusets to Florida, west
to Texas and Minnesota.
||Rich fertile woods and hillsides[43, 82] in deep
|Other Posible Synonyms:
||From various places across the web, may not be correct.
|J. duclouxiana[G] J. fallax[G] J. kamaonica[G] J.
orientis[G] J. regia[B,C,E,G,H,P] J. regia subsp. kamaonica[G] J. regia
var. orientis[G] J. regia var. sinensis[G] J. sinensis[G] Wallia
|Other Common Names:
||From various places around the Web, may not be correct.
|Black Walnut [B,H,P], Ceviz Agaci [E], Ch'Iang T'Ao [E],
Common Walnut [H], English Walnut [P,H,B], Guz [E], Hei T'Ao [E], Hu
T'Ao [E], Hu Tao [E], Jawiz [E], Joz [E], Nogal [E], Persian Walnut [H],
Qoz [E], Walnut [H], Walnut,Black [E],
||From a Dictionary
of Botanical Epithets
|nigra = black;
|Other Range Info:
||From the Ethnobotany
|China; India; Iraq; Mexico; Nepal; Spain; Turkey; Us
A decidious tree growing to 30m by 20m at a fast rate. It is hardy to zone 4
and is frost tender. It is in flower from May to June, and the seeds ripen in
October. The scented flowers are monoecious (individual flowers are either male
or female, but both sexes can be found on the same plant) and are pollinated by
Wind. The plant is self-fertile. We rate it 3 out of 5 for usefulness.
The plant prefers light (sandy), medium (loamy) and heavy (clay) soils and
requires well-drained soil. The plant prefers acid, neutral and basic (alkaline)
soils. It cannot grow in the shade. It requires moist soil.
Oil; Sap; Seed; Sweetener.
Seed - raw or cooked. A sweet, rich distinctive delicious flavour it makes an
excellent dessert nut and is also widely used in confections, cakes etc[2, 34,
82, 183]. The kernel is hard to extract and the oil it contains quickly turns
rancid[101, 159]. The unripe fruits can be pickled. The seed is borne in
solitary fruits or in pairs and is 3 - 4cm in diameter[82, 229]. The nuts can
leave a permanent stain on clothing.
An edible oil is obtained from the seed[101, 183]. A sweet taste but it tends to
go rancid quickly. Used as a seasoning in bread, squash and other
The tree yields a sweet sap that can be drunk or concentrated into syrup or
sugar[101, 102, 183]. It is tapped in spring.
Compost; Dye; Filter; Herbicide; Insecticide; Repellent; Tannin; Wood.
A brown dye is obtained from the nuts, husks and bark[14, 57, 101, 159]. It
does not require a mordant. The husks can be dried for later use.
A brown dye is obtained from the leaves and stems. It does not require a
mordant. The dye turns black if it is prepared in an iron pot. The
leaves can be dried for later use.
The husks are rich in tannin.
The husks can be made into a high quality coal (does the report mean charcoal?[K])
and is then used as a filter. It was used in gas masks.
The leaves repel fleas and have been used as a strewing herb[20, 201, 257]. They
are also used as an insecticide against bed bugs. The ground up husks are
The leaves produce substances that depress the growth of other plants. These
substances are washed onto the ground by rain and inhibit the growth of plants
beneath the tree[18, 20, 159]. The roots also produce substances that are toxic
to many plant species, especially apples (Malus species), members of the
Ericaceae, Potentilla spp and the white pines (certain Pinus spp.).
An alternative ingredient of 'QR' herbal compost activator. This is a dried
and powdered mixture of several herbs that can be added to a compost heap in
order to speed up bacterial activity and thus shorten the time needed to make
Wood - very ornamental heavy, hard, strong, close-grained, very durable. Easily
worked, it glues well, does not warp, shrink or swell much and takes a good
polish. It weighs 38lb per cubic foot. A very valuable timber tree and possibly
the most sought after wood in N. America, it is used in cabinet making, ship
building, veneer etc[1, 46, 61, 82, 101, 149, 227, 229, 235].
Requires a deep well-drained loam and a sunny position sheltered from strong
winds[1, 11]. Prefers a slightly alkaline soil.
The dormant plant is very cold hardy, but the young growth in spring, however,
can be damaged by late frosts.
The black walnut is a very ornamental and fast growing plant[1, 200], it is
sometimes cultivated in N. America for its edible seed. There are breeding
programmes that are seeking to develop cultivars with thinner shells. Trees
in the wild commence bearing seeds when about 12 years old. There are some
named varieties. Trees do not fruit very freely in Britain unfortunately[1,
11]. They grow well in the eastern half of the country but often do not thrive
in the west. Trees have been extensively planted for timber in parts of C.
and E. Europe.
This species hybridizes with J. regia, some named cultivars have been
developed for their seed.
Plants produce a deep taproot and they are intolerant of root disturbance[1,
11]. Seedlings should be planted out into their permanent positions as soon as
possible and given some protection for their first winter or two since they are
somewhat tender when young[1, 11].
Flower initiation depends upon suitable conditions in the previous summer.
The flowers and young growths can be destroyed by even short periods down to -2°c,
but fortunately plants are usually late coming into leaf.
Any pruning should only be carried out in late summer to early autumn or when
the plant is fully dormant otherwise wounds will bleed profusely and this will
severely weaken the tree.
Plants produce chemicals which can inhibit the growth of other plants. These
chemicals are dissolved out of the leaves when it rains and are washed down to
the ground below, reducing the growth of plants under the tree[18, 20, 159]. The
roots also produce substances that are toxic to many plant species, especially
apples (Malus species), members of the Ericaceae, Potentilla spp and the white
pines (certain Pinus spp.). Beans, peas and tomatoes are also particularly
sensitive to these secretions and will not grow in the rooting zone. Trees
cast quite a dense shade so, along with their other anti-social tendencies, are
not very friendly trees for a woodland garden[K].
The bruised leaves have a pleasant sweet though resinous smell.
The seed is best sown as soon as it is ripe in individual deep pots in a cold
frame. You need to protect it from mice, birds, squirrels etc. The seed
usually germinates in late winter or the spring. Plant out the seedlings into
their permanent positions in early summer and give some protection from the cold
for their first winter or two.
The seed can also be stored in cool moist conditions (such s the salad
compartment of a fridge) over the winter and sown in early spring but it may
then require a period of cold stratification before it will germinate[78, 80,
- Leaves: Crushed
- The bruised leaves have a pleasant sweet though resinous smell.
- No entries have been made for this species as yet.
PFAF Web Pages
This plant is mentioned in the following web pages
References for Juglans regia (a possible synonym).
- Details of Medicinal Uses, Habitats, etc. in M. Grieve A
Modern Herbal (1931) 
- [H] Details of Scandanavian and European Common names in Henriette's
- [E] Ethnobotany
Data (common names, uses, countries) from the Ethnobotany
- [B] Data
(Latin & Common names, other references) from the BONAP's Synonymized
Checklist of the Vascular Flora of the United States, Puerto Rico, and the
- [G] Data
(Common Names, Uses, Distribution) from the USDA/ARS NPGS's GRIN
- [P] Data.
(uses, distribution, wetland) from the UDSA's
See the PFAF Links
Pages for other sources or the The
Gatherer where you can search many other sources all in one go.
[K] Ken Fern
Notes from observations, tasting etc at Plants For A Future and on field trips.
 F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956
Oxford University Press 1951
Comprehensive listing of species and how to grow them. Somewhat outdated, it has
been replaces in 1992 by a new dictionary (see ).
 Hedrick. U. P. Sturtevant's Edible Plants of the World.
Dover Publications 1972 ISBN 0-486-20459-6
Lots of entries, quite a lot of information in most entries and references.
 Grieve. A Modern Herbal. Penguin 1984 ISBN 0-14-046-440-9
Not so modern (1930's?) but lots of information, mainly temperate plants.
 Bean. W. Trees and Shrubs Hardy in Great Britain. Vol 1 - 4
and Supplement. Murray 1981
A classic with a wealth of information on the plants, but poor on pictures.
 Holtom. J. and Hylton. W. Complete Guide to Herbs.
Rodale Press 1979 ISBN 0-87857-262-7
A good herbal.
 Philbrick H. and Gregg R. B. Companion Plants. Watkins
Details of beneficial and antagonistic relationships between neighbouring
 Riotte. L. Companion Planting for Successful Gardening.
Garden Way, Vermont, USA. 1978 ISBN 0-88266-064-0
 Lust. J. The Herb Book. Bantam books 1983 ISBN
Lots of information tightly crammed into a fairly small book.
 Bruce. M. E. Commonsense Compost Making. Faber 1977 ISBN
Excellent little booklet dealing with how to make compost by using herbs to
activate the heap. Gives full details of the herbs that are used.
 Harrison. S. Wallis. M. Masefield. G. The Oxford Book of Food
Plants. Oxford University Press 1975
Good drawings of some of the more common food plants from around the world. Not
much information though.
 Fernald. M. L. Gray's Manual of Botany. American Book
A bit dated but good and concise flora of the eastern part of N. America.
 Uphof. J. C. Th. Dictionary of Economic Plants. Weinheim
An excellent and very comprehensive guide but it only gives very short
descriptions of the uses without any details of how to utilize the plants. Not
for the casual reader.
 ? Flora Europaea Cambridge University Press 1964
An immense work in 6 volumes (including the index). The standard reference flora
for europe, it is very terse though and with very little extra information. Not
for the casual reader.
 Schery. R. W. Plants for Man.
Fairly readable but not very comprehensive. Deals with plants from around the
 Usher. G. A Dictionary of Plants Used by Man. Constable
1974 ISBN 0094579202
Forget the sexist title, this is one of the best books on the subject. Lists a
very extensive range of useful plants from around the world with very brief
details of the uses. Not for the casual reader.
 Sheat. W. G. Propagation of Trees, Shrubs and Conifers.
MacMillan and Co 1948
A bit dated but a good book on propagation techniques with specific details for
a wide range of plants.
 McMillan-Browse. P. Hardy Woody Plants from Seed. Grower
Books 1985 ISBN 0-901361-21-6
Does not deal with many species but it is very comprehensive on those that it
does cover. Not for casual reading.
 Sargent. C. S. Manual of the Trees of N. America. Dover
Publications Inc. New York. 1965 ISBN 0-486-20278-X
Two volumes, a comprehensive listing of N. American trees though a bit out of
date now. Good details on habitats, some details on plant uses. Not really for
the casual reader.
 Gordon. A. G. and Rowe. D. C. f. Seed Manual for Ornamental
Trees and Shrubs.
Very comprehensive guide to growing trees and shrubs from seed. Not for the
 Turner. N. J. and Szczawinski. A. Edible Wild Fruits and
Nuts of Canada. National Museum of Natural Sciences 1978
A very readable guide to some wild foods of Canada.
 Kavasch. B. Native Harvests. Vintage Books 1979 ISBN
Another guide to the wild foods of America.
 Dirr. M. A. and Heuser. M. W. The Reference Manual of Woody
Plant Propagation. Athens Ga. Varsity Press 1987 ISBN 0942375009
A very detailed book on propagating trees. Not for the casual reader.
 Vines. R. A. Trees of Central Texas. University of
Texas Press 1987 ISBN 0-292-78958-3
Fairly readable, it gives details of habitats and some of the uses of trees
growing in Texas.
 McPherson. A. and S. Wild Food Plants of Indiana.
Indiana University Press 1977 ISBN 0-253-28925-4
A nice pocket guide to this region of America.
 Grae. I. Nature's Colors - Dyes from Plants. MacMillan
Publishing Co. New York. 1974 ISBN 0-02-544950-8
A very good and readable book on dyeing.
 Buchanan. R. A Weavers Garden.
Covers all aspects of growing your own clothes, from fibre plants to dyes.
 Facciola. S. Cornucopia - A Source Book of Edible Plants.
Kampong Publications 1990 ISBN 0-9628087-0-9
Excellent. Contains a very wide range of conventional and unconventional food
plants (including tropical) and where they can be obtained (mainly N. American
nurseries but also research institutes and a lot of other nurseries from around
 Huxley. A. The New RHS Dictionary of Gardening. 1992.
MacMillan Press 1992 ISBN 0-333-47494-5
Excellent and very comprehensive, though it contains a number of silly mistakes.
Readable yet also very detailed.
 Allardice.P. A - Z of Companion Planting. Cassell
Publishers Ltd. 1993 ISBN 0-304-34324-2
A well produced and very readable book.
 Foster. S. & Duke. J. A. A Field Guide to Medicinal
Plants. Eastern and Central N. America. Houghton Mifflin Co. 1990 ISBN
A concise book dealing with almost 500 species. A line drawing of each plant is
included plus colour photographs of about 100 species. Very good as a field
guide, it only gives brief details about the plants medicinal properties.
 Lauriault. J. Identification Guide to the Trees of Canada
Fitzhenry and Whiteside, Ontario. 1989 ISBN 0889025649
Very good on identification for non-experts, the book also has a lot of
information on plant uses.
 Vines. R.A. Trees of North Texas University of Texas
Press. 1982 ISBN 0292780206
A readable guide to the area, it contains descriptions of the plants and their
habitats with quite a bit of information on plant uses.
 Elias. T. The Complete Trees of N. America. Field Guide and
Natural History. Van Nostrand Reinhold Co. 1980 ISBN 0442238622
A very good concise guide. Gives habitats, good descriptions, maps showing
distribution and a few of the uses. It also includes the many shrubs that
occasionally reach tree proportions.
 Britton. N. L. Brown. A. An Illustrated Flora of the
Northern United States and Canada Dover Publications. New York. 1970 ISBN
Reprint of a 1913 Flora, but still a very useful book.
 Genders. R. Scented Flora of the World. Robert Hale.
London. 1994 ISBN 0-7090-5440-8
An excellent, comprehensive book on scented plants giving a few other plant uses
and brief cultivation details. There are no illustrations.
 Moerman. D. Native American Ethnobotany Timber Press.
Oregon. 1998 ISBN 0-88192-453-9
Very comprehensive but terse guide to the native uses of plants. Excellent
bibliography, fully referenced to each plant, giving a pathway to further
information. Not for the casual reader.
Black Walnut Toxicity to Plants, Humans and Horses
Richard C. Funt
The roots of Black Walnut (Juglans nigra L.) and Butternut (Juglans
cinerea L.) produce a substance known as juglone
(5-hydroxy-alphanapthaquinone). Persian (English or Carpathian) walnut trees are
sometimes grafted onto black walnut rootstocks. Many plants such as tomato,
potato, blackberry, blueberry, azalea, mountain laurel, rhododendron, red pine
and apple may be injured or killed within one to two months of growth within the
root zone of these trees. The toxic zone from a mature tree occurs on average in
a 50 to 60 foot radius from the trunk, but can be up to 80 feet. The area
affected extends outward each year as a tree enlarges. Young trees two to eight
feet high can have a root diameter twice the height of the top of the tree, with
susceptible plants dead within the root zone and dying at the margins.
Not all plants are sensitive to juglone. Many trees, vines, shrubs,
groundcovers, annuals and perennials will grow in close proximity to a walnut
tree. Certain cultivars of "resistant" species are reported to do
poorly. Black walnut has been recommended for pastures on hillsides in the Ohio
Valley and Appalachian mountain regions. Trees hold the soil, prevent erosion
and provide shade for cattle. The beneficial effect of black walnut on pastures
in encouraging the growth of Kentucky bluegrass (Poa pratensis L.) and
other grasses appears to be valid as long as there is sufficient sunlight and
Gardeners should carefully consider the planting site for black walnut,
butternut, or persian walnut seedlings grafted to black walnut rootstock, if
other garden or landscape plants are to be grown within the root zone of mature
trees. Persian walnut seedlings or trees grafted onto Persian walnut rootstocks
do not appear to have a toxic effect on other plants.
Horses may be affected by black walnut chips or sawdust when they are used
for bedding material. Close association with walnut trees while pollen is being
shed (typically in May) also produce allergic symptoms in both horses and
humans. The juglone toxin occurs in the leaves, bark and wood of walnut, but
these contain lower concentrations than in the roots. Juglone is poorly soluble
in water and does not move very far in the soil.
Walnut leaves can be composted because the toxin breaks down when exposed to
air, water and bacteria. The toxic effect can be degraded in two to four weeks.
In soil, breakdown may take up to two months. Black walnut leaves may be
composted separately, and the finished compost tested for toxicity by planting
tomato seedlings in it. Sawdust mulch, fresh sawdust or chips from street tree
prunings from black walnut are not suggested for plants sensitive to juglone,
such as blueberry or other plants that are sensitive to juglone. However,
composting of bark for a minimum of six months provides a safe mulch even for
plants sensitive to juglone.
Plants Observed Growing Under or Near Black Walnut*
- 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
- Virginia Creeper, Parthenocissus quinquefolia
- ** Pinxterbloom, 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
- Pot-marigold, Calendula officinalis 'Nonstop'
- Begonia, fibrous cultivars
- Morning Glory, Ipomoea 'Heavenly Blue'
- Pansy Viola
- Zinnia species
- Squashes, Melons, Beans, Carrots, Corn
- Peach, Nectarine, Cherry, Plum
- Prunus species Pear-Pyrus species
- 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
- Spanish Bluebell, Endymion hispanicus
- 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'
- Common Hyacinth, Hyacinthus Orientalis 'City of Haarlem'
- Virginia Waterleaf, Hydrophyllum virginianum
- Siberian Iris, Iris sibirica
- Balm, Monarda didyma
- Wild Bergamot, M. fistulosa
- Grape Hyacinth, Muscari botryoides
- Sweet Cicely, Myrrhis odorata 'Yellow Cheerfulness,' 'Geranium,'
'Tete a Tete,' 'Sundial,' and 'February Gold'
- 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
- Siberian Squill, Scilla sibirica
- Goldmoss Stonecrop, Sedum acre
- Showy Sedum, Sedum spectabile
- Lamb's-Ear, Stachys byzantina
- Spiderwort, Tradescantia virginiana
- Nodding Trillium, Trillium cernuum
- White Wake-Robin, Trillium grandiflorum
- Tulipa Darwin 'White Valcano' and 'Cum Laude,' Parrot 'Blue
Parrot,' Greigii 'Toronto'
- Big Merrybells, Uvularia grandiflora
- Canada Violet, Viola canadensis
- Horned Violet, Viola cornuta
- Woolly Blue Violet, Viola sororia
*These are based upon observations and not from clinical tests.
**Cultivars of some species may do poorly.
Plants That Do Not Grow Within 50 Feet of Drip Line of Black Walnut
- 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)
- Alfalfa, Medicago sativa
- Buttercup, Narcissus 'John Evelyn,' 'Unsurpassable' 'King Alfred'
and 'Ice Follies'
- Peonies, *Paeonia species (some)
- Rhubarb, Rheum rhabarbarum
- 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
- Red Chokeberry, Aronia arbutifolia
- Hydrangea species
- Mountain Laurels, Kalmia species
- Privet, Ligustrum species
- Amur Honeysuckle, Lonicera maackii
- Brush Cinquefoil, Potentilla species
- Rhododendrons and Azaleas, **Rhododendron species (most)
- 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
- double-flowered cole vegetables
*Cultivars of some species may survive but will do poorly.
The authors express their appreciation to Drs. M. Scott Biggs, Department of
Horticulture and Crop Science, and Harry Hoitink, Department of Plant Pathology,
for their review and additional comments.