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Permaculture Plants: Walnut Trees





  • What may be the largest Black Walnut tree in the world on Sauvie Island, Oregon.
    Note the man standing to the right of the base of the tree.

    Common Name: Walnut (Black, English, Persian, Carpathian)
    Scientific Name:

    Juglans nigra (Black Walnut)
    Juglans regia (English/Persian Walnut, Carpathian Walnut)
    Family: Juglandaceae


    Comparison of Black Walnut (left) to English/Persian Walnut (right)
    Each plate contains all meat from 10 walnuts of each species

    Description:

     This very large deciduous tree is a popular nut and lumber tree.  There are 21 species of tree in theJuglans genus.  The most commonly grown tree for nuts is the English or Persian Walnut.  The Carpathian Walnut is a more cold-hardy variety of the English/Persian Walnut, but many people consider them interchangeable.  In the United States, the Eastern Black Walnut is a very common tree for nuts, which is prized for its stronger flavor but much more difficult extraction; however, it may be even more valued for its high quality wood from a relatively fast growing tree.  Walnuts are great shade trees, great nut producers, and may be considered a wise investment for your children or grandchildren.

    English Walnut 1901 – A.W. Mumford


    History:

     The English/Persian Walnut is native to Central Asia.  Alexander the Great introduced this tree to Macedonia and Greece in the 4th century B.C.  The Romans continued this spread throughout Europe, England, and northern Africa.  It was introduced to the Americas in the 17th century by colonists.

    The Black Walnut is native to the eastern United States.  It was introduced to Europe in 1629 to be used primarily as a high quality wood tree.  It is more cold-hardy than the English/Persian Walnut.

    Trivia:

    • Walnuts are the second larges nut crop in North America, second to almonds
    • The Black Walnut has a stronger flavor and more crunch than the English/Persian Walnut but is way more difficult to extract the nut meat
    • Walnuts can be tapped in spring and produces a sweet sap that can be drunk or boiled down into syrup
    • The Black Walnut is a very valuable tree, and there are actually walnut tree poachers in the United States – one case involved a 55 ft (16 m) tree that was worth $2500 in 2004
    • Many English/Persian Walnuts are planted on Black Walnut root stock
    • The Black Walnut is the host plant for caterpillars of the luna and regal moths – beautiful


    Beautiful Black Walnut in autumn.

    USING THIS PLANT
    Primary Uses:

    • Fresh eating (raw)
    • Roasted
    • Dried
    • High quality lumber – very hard and very pretty, so it is used for flooring, furniture, and things like gunstocks, paddles, and tools


    Secondary Uses:

    • Walnut oil
    • Hulls can make a brown dye for yarn, cloth, etc. and can even be used as a wood stain.
    • Walnuts can be tapped like a maple tree to make syrup
    • Dynamic accumulator (Need definition) – Potassium, Phosphorus (Black Walnuts also accumulate Calcium)
    • General insect pollen source
    • Extracts from the green husks of walnuts have insecticidal properties
    • Can be coppiced
    • Medicinal uses: nuts contain antioxidants, appear to protect the arteries, and may slow cognitive-decline


    English/Persian Walnuts about to break from their husks while still on the tree.

    Black Walnuts ripen in their husks, but the husks do not break open on the tree.

    A ripe and recently husked Black Walnut nut – not an easy process!

    Yield:
    Depends on the size and age of the tree:

    Juglans nigra (Black Walnut) – 20 lbs (9 kg) to 100 lbs (45 kg)
    Juglans regia (English/Persian Walnut) – up to 6 bushels (210 liters); produces more than J. nigra

    Harvesting:

    • Late August – October, depends on species, variety, and USDA Zone
    • English Walnut nuts will fall from green husks when ripe.  Usually pick nuts from the ground or from nut catching nets if you place them and then shake the tree.  Commercial nut producers will have tree-shakers.
    • Black Walnut nuts fall with husk in place.  The husk must be removed to get to the nut which must be shelled to get to the meat.  They nuts taste better when the husk is still green and not black.  There are many methods to extract the nut from the husk, but a hammer is often used.  Once the nut is extracted (this process will stain everything), toss out nuts that are black and oily.  Drop the rest of them in a bucket of water, and toss out the ones that float.  Drain the nuts and lay them out in a warm, dry location.  You can let them cure for over a month.  Toss out any that become moldy.  Then crack the nuts – a mounted vise works well – but be warned that cracking Black Walnut nuts can cause sharp shells to go flying.  All this work is worth it if you’ve ever really compared the taste of Black Walnuts with the more mild English/Persian Walnuts.


    Storage: Dried nuts will store for 2-3 years

    Black Walnut (top) and English/Persian Walnut (bottom) leaves

    Black Walnut bark.
    English/Persian Walnut bark has wider grooving.


    DESIGNING WITH THIS PLANT
    USDA Hardiness Zone:

    Juglans nigra (Black Walnut) – Zone 4-7
    Juglans regia (Carpathian Walnut) – Zone 5-7
    Juglans regia (English/Persian Walnut) – Zone 7-9


    AHS Heat Zone: 4-9
    Chill Requirement: 400-1,500 hours/units depending on the species and variety

    Plant Type: Large Tree
    Leaf Type: Deciduous
    Forest Garden Use: Canopy Tree
    Cultivars/Varieties: Many varieties available.

    Pollination: Some varieties are self-fertile (self-pollinating), and some are not.  Most will have higher yields if they can cross-pollinate
    Flowering: Late spring (May)

    Life Span:
    Years to Begin Bearing: 4-5 years for grafted varieties, 4-12 years from seedling
    Years to Maximum Bearing: 10-15 years
    Years of Useful Life: 100+ years

    The flowers of the walnut tree.

    PHYSICAL CHARACTERISTICS OF THIS PLANT
    Size: 75-130 feet (25-40 meters) tall and wide, will grow taller if there is light competition
    Roots: Taproot
    Growth Rate: Medium to Fast (Black Walnuts grow faster)

    Looking up into a Black Walnut.

    GROWING CONDITIONS FOR THIS PLANT
    Light: Prefers full sun
    Shade: Tolerates light shade (about 50%)
    Moisture: Medium moisture.  The Black Walnut can tolerate less moist soils.
    pH: 6.1-7.5 (Neutral to slightly alkaline)

    Special Considerations for Growing:

    • Walnut roots and leaves produce juglone, a chemical that inhibits the growth of certain plants.  Make sure that surrounding trees and underplanted plants can tolerate juglone.
    • Black Walnuts can be difficult to shell – just make sure you have a heavy-duty nut cracker.  I’ve read about people who just run over them with their car to minimize the hassle, but the hassle is worth it!
    • Certain Walnut specific diseases exist.  Choose disease resistant varieties to avoid these problems.
    • Rodents can be a problem for seedlings and young trees – they like to eat the bark.


    Propagation:
    Usually grafted from improved varieties.  Walnuts grown from seed or wild stock typically have nuts that do not taste as good, and they also take longer to start producing a harvest; however, they are just fine for wood.  If starting from seed, they will need 90 days stratification.

    Maintenance:
    If planning on using as lumbar, then prune for a strong central leader.  Otherwise, they don’t need much once established.

    Concerns:

    • This is a large tree.  Only raise it if you have the space or plan on cutting it down before it gets too large.
    • Walnut roots and leaves produce juglone, a chemical that inhibits the growth of certain plants.  Make sure that surrounding trees and underplanted plants can tolerate juglone.


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