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Walnut Trees and Soil Toxicity

© Jojo Sigurgeirson

The walnut tree produces some beautiful wood products. Apparently it is the absolute best wood for fashioning a humidor, and is apparently a good internal cleanser. Black Walnut bark has been used as a vermifuge for centuries in Asia. It's used as a cure for atheletes foot, and the nuts are delicious, particularly once they've cured for a month to 6 weeks.

Walnuts have been recognized as one the oldest tree foods known to man, dating back to about 7000 B.C. Considered food for the gods in the early days of Rome, walnuts were named "Juglans regia" in honor of Jupiter. Today, they are commonly called "English" walnuts, in reference to the English merchant marines whose ships once transported the product for trade to ports around the world. Historians prefer the name "Persian" walnuts, referring to Persia, the birthplace of walnuts.

Walnuts are also a real pain in the garden, because they emit a toxic substance which hinders the growth of other plants. The roots of the black walnut contain a chemical called juglone that kills the roots of other plants that touch the roots of black walnut trees. As well, leaves of the black walnut affect other plants, so conscientious raking is necessary. Some people say rain dripping from the crown and dropline of the tree also affects plants around it. The chemical can take several years to kill a succeptible plant. Among landscape plants, evergreens are most susceptible to juglone. The roots of the black walnut extend beyond the tips of the outermost branches. For this reason, many gardens with black walnut trees have very little growing beneath them.

I have a large black walnut tree in my garden, so I've been researching this subject quite alot. There are many factors that go into finding a suitable plant for any problem location.

Perennials
Ajuga reptans
Alcea rosea
Anemone japonica
Asarum europaeum (Wild Ginger)
Astilbe
Campanula latifolia
Chrysanthemum
Cyclamen hederifolium (Cyclamen)
Doronicum (Leopard's Bane)
Epimedium (Bishops Hat)
Erythronium (Dog's Tooth Violet)
Galium odoratum
Gentiana sino-ornata
Gentiana septemnifida
Geranium endressii
Geranium phaeum
Geranium pratense
Geranium robertianum
Geranium sanguineum
Hedera helix (English Ivy)
Helianthus tuberosus (Jerusalem artichoke)
Hemerocallis fulva (common Dayliy)
Heuchera
Hieracium aurantiacum (orange hawkweed)
Hosta lancifolia
Hosta marginata
Hosta undulata
Hydrophyllum virginianum
Iris germanica
Iris siberica
Liriope
Monarda didyma
Monarda fistulosa
Oenothera fruticosa (Sundrops)
Ophiopogon
Pachysandra terminalis
Phlox paniculata
Polemonium reptans (Jacob's Ladder)
Polygonatum commutatum (Great Solomon's Seal)

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