Juglone in Black Walnut Trees

This natural Toxin is deadly to many Plants, Shrubs, and Trees

Tomatoes are especially sensitive to this Toxin, which makes them a good indicator of the presence of this contaminant. They droop and have the appearance of underwatering or Blight.

It is found in the Leaves, Bark, Roots, and Husks. Some Gardeners think that  Composting the Tree parts neutralizes this Toxin, while other Gardeners think it even survives Composting

Juglone is produced in the various parts of a tree in different concentrations. Weather and soil conditions influence the amount of Juglone produced. Depending on the size of the tree and the tolerance of a particular Plant, an intolerant plant may be stunted or killed by the contaminant.

INTOLERANT Plants, Shrubs, and Trees.


apple
azalea
birch, white
blackberry
blueberry
cherry
chrysanthemum
crocus, autumn
forget-me-not
grape, domestic
lily-of-the-valley
linden
mountain laurel
peas
peony
pine
potato
rhododendron
thyme
tomato

TOLERANT Plants, Shrubs, and Trees:


anemone
aster
astilbe
bee balm
begonia
bittersweet
calendula
clematis (virginsbower)
coral bells
creeper, Virginia
daffodil
daisy, shasta
daylily
evening primrose
fern
geraniums, hardy
goldenrod
grape, wild
hollyhock
hosta
hyacinth, grape; oriental
iris, siberian
ironweed
jack-in-the-pulpit
lamb's ear
liriope
lobelia
may apple
morning glory
mullein
phlox
primrose
raspberry, black
rose, wild
rudbeckia
scilla
sedum
speedwell
spiderwort
St. John's wort
sunflower
trillium
tulip
violet
wisteria
yarrow
arborvitae, American
ash, white
barberry
beech, American
birch, black; 'Heritage' river
boxelder
buckeye, Ohio
catalpa
cherry, black
crabapple
daphne
dogwood, flowering
elderberry
elm, American
forsythia
fringetree
goldenraintree
globeflower
gum, black
hawthorn
hemlock, Canadian
hibiscus
hickory
holly, American
honeylocust
honeysuckle, amur; tatarian
hydrangea
lilac
locust, black
maple, red; sugar; black; Japanese
ninebark
oak, white; red; scarlet
pawpaw
pear, callery
pine, Virginia
privet
red cedar, eastern
redbud, eastern
sassafrass
serviceberry
silverbell, Carolina
spruce, Norway
sumac
sweetgum
sycamore
tulip tree
viburnums (some)
witchhazel


Juglone may contaminate the soil occupied by a Walnut, Hickory, or Butternut tree 
many months and even years after the tree dies or is removed. An area as much as 60 feet from the tree may be contaminated. Trees less than five years old do not seem to produce enough Toxin to be lethal to most Plants.

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