Juglans nigra

One of the best Native Trees. A most important tree in any landscape. For nutrition, timber, beauty, nutrition and shade, Black Walnuts are defined with the fabric of nature and living things. Zone 4 - 9

Black Walnut & Carpathian Persian Walnut

Black Walnuts

Magnificent deciduous trees to 150' with rough nuts that are prized for their rich, oily, distinctively flavored kernels. These are harvested in the fall.

Culture
Like other nuts, black walnuts can be grown from seed but do not come true; so buy grafted varieties.

The trees have deep roots and require a deep soil that is above average in quality, well drained and moisture retentive. Provide a pH of 6.0 to 6.5. Plant the tree at the depth previously grown. Each tree needs a space of about 60' in diameter, although in a plantation that is grown for timber as well as nuts, trees are often started out 20' apart and gradually thinned.

Do not plant black walnuts near apple trees or the vegetable garden, because the roots contain the toxic substance juglone that damages these plants. In a lawn area, the fallen nuts make mowing difficult. (see below for some plants that are sensitive and some that are tolerant to juglone).

Water trees regularly during their first year and in dry periods there after. Fertilize in the spring with a 10-10-10 mixture at the rate of 1 cup per year of tree age; however, trees that are making strong growth need to be fed only every 2nd or 3rd year. Maintaining a mulch of organic matter around the trees help to nourish them.

Black walnuts need little pruning except to remove dead and damaged wood and suckers developing below the graft. You must keep an eye on them, to see they develop only a single, straight trunk and main branches with wide crotches. If a tree is grown for timber or as an ornamental specimen in an open area, the lower limbs can be removed gradually as the tree shoots upward. Cut out these limbs before they exceed 1" in diameter.

Black walnuts start bearing 3 to 6 years after planting. Harvest the nuts as soon as they fall from the tree. At this point they have mild, light colored kernels. If left on the ground so the husks can decompose, the kernels are dark colored and more strongly flavored. Remove the husks with a hammer or by rolling them across a rough pavement under a heavy boot. Then wash the nuts and spread them out in a shady, ventilated place to dry for several weeks. They can then be stored in a cool, dry place.

To facilitate cracking of walnuts and other hard-shelled nuts, sprinkle them with water and put them in a tight can with a damp sponge for 12 hours or more. This softens the kernels slightly and allows you to remove them in larger pieces. Grafted varieties crack our easier than wild seedlings.

Carpathian Walnuts

The Carpathian walnut is a Persian walnut similar to the English walnut grown in the Far West but considerably hardier. It grows in zones 5 - 8, but does best in 6. Self fruitful, but like other walnuts you get better nut crops if you plant two different varieties together.

Culture
Carpathian walnuts are grown much like English walnuts. Plant on a north slope so the sun will be slow to force them into growth in spring. Avoid frosty locations. The soil should be deep, fertile, and well drained.

Give each tree a space 50 feet across. Fertilize with ammonium nitrate or a high-nitrogen balanced fertilizer such as 20-10-10. Minor elements may also be needed. 1 cup for each year of age. Young trees can grow with little or no fertilizers, so, fertilize as needed. Trees start to bear in 3 to 5 years. Harvest nuts when they drop.

Nuts are large, light brown and have delicious light brown kernels differing from black walnuts in that they are milder and less oily, and easier to open and remove the kernel. The husks open on the tree and show the nuts. So, they are easier to harvest than Black Walnuts.

Mulching with an organic material is highly recommended, at least while the trees are reasonably small.

Pruning consists of training to a modified leader with 4 or 5 scaffold branches. If these and other branches grow unusually long in any year before the trees start to bear, they should be headed back 1/3 to 1/2 to keep them from bending down to the ground under the weight of the nuts. Although regular pruning of mature trees was once considered unnecessary, it is now recommended - especially for the very fruitful new varieties. The main aim should be to keep the tops thinned out to allow light to penetrate and to encourage more vigorous branch growth.

To facilitate cracking of walnuts and other hard-shelled nuts, sprinkle them with water and put them in a tight can with a damp sponge for 12 hours or more. This softens the kernels slightly and allows you to remove them in larger pieces. Grafted varieties crack our easier than wild seedlings.

Plants Observed to Be Sensitive to Juglone

Vegetables: asparagus, cabbage, eggplant, pepper, potato, rhubarb, tomato.

Fruits: apple, blackberry, blueberry, pear.

Landscape plants: black alder; azalea; basswood; white birch; ornamental cherries; red chokeberry; crabapple; hackberry; Amur honeysuckle; hydrangea; Japanese larch; lespedeza; lilac; saucer magnolia; silver maple; mountain laurel; pear; loblolly pine; mugo pine; red pine; scotch pine; white pine; potentilla; privet; rhododendron; Norway spruce; viburnum (few); yew.

Flowers and herbaceous plants: autumn crocus (Colchicum); blue wild indigo (Baptisia); chrysanthemum (some); columbine; hydrangea; lily; narcissus (some); peony (some); petunia; tobacco.

Field crops: alfalfa; crimson clover; tobacco.

Plants Observed to Be Tolerant to Juglone

Vegetables: lima bean; snap bean; beet; carrot; corn; melon; onion; parsnip; squash. Fruits: black raspberry, cherry.

Landscape plants: arborvitae; autumn olive; red cedar; catalpa; clematis; crabapple; daphne; elm; euonymous; forsythia; hawthorn; hemlock; hickory; honeysuckle; junipers; black locust; Japanese maple; maple (most); oak; pachysandra; pawpaw; persimmon; redbud; rose of sharon; wild rose; sycamore; viburnum (most); Virginia creeper.

Flowers and herbaceous plants: astilbe; bee balm; begonia; bellflower; bergamot; bloodroot; Kentucky bluegrass; Spanish bluebell; Virginia bluebell; bugleweed; chrysanthemum (some); coral bells; cranesbill; crocus; Shasta daisy; daylily; Dutchman's breeches; ferns; wild ginger; glory-of-the-snow; grape-hyacinth; grasses (most); orange hawkweed; herb Robert; hollyhock; hosta (many); hyacinth; Siberian iris; Jack-in-the pulpit; Jacob's ladder; Jerusalem artichoke; lamb's-ear; leopard's-bane; lungwort; mayapple; merrybells; morning glory; narcissus (some); pansy; peony (some); phlox; poison ivy; pot marigold; polyanthus primrose; snowdrop; Solomon's-seal; spiderwort; spring beauty; Siberian squill; stonecrop; sundrop; sweet Cicely; sweet woodruff; trillium; tulip; violet; Virginia waterleaf; winter aconite; zinnia.

Toxicity list compiled by Purdue University Cooperative Extension Service

Ref; "Gardens are for Eating" by Schuler 1971 publisher MacMillan & Co.