|
| Name |
Ornamental
- Juglans Nigra - Black Walnut |
| Cultivation |
Light: Black walnut is intolerant of shade. Plant in full sun.
Moisture: It likes a moist, well drained soil.
Hardiness: hardy in Britain and Ireland.
Requires a deep well-drained loam and a sunny position sheltered from
strong winds. Prefers a slightly alkaline soil. Plants are best suited
to deep, rich, slightly acid or neutral soil, with good drainage, but
will not succeed on infertile upland soil or on soils with poor drainage.
The black walnut grows best areas with an annual precipitation from 30
to 130cm, an annual temperature in the range of 7 to 19°C and a pH
from 4.9 - 8.2. The dormant plant is very cold hardy, but the young growth
in spring, however, can be damaged by late frosts.
Plants produce a deep taproot which makes them very drought resistant
when established, though they are intolerant of root disturbance. 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.
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.
|
| Family |
Juglandaceae
|
| Genus |
Genus:
Juglans
Species: J. nigra |
| Synonyms |
Black
Walnut or American Walnut |
| Known
Hazards |
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. The roots also
produce substances that are toxic to many plant species, especially apples
(Malus species), 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. The bruised leaves have a pleasant
sweet smell. |
| Range |
Trees
in the wild commence bearing seeds when about 12 years old. Black walnut
trees mature their fruit rather generally throughout the plants natural
range where there is a growing season of about 150 days and an average summer
temperature of 16.5°C. Trees do not fruit very freely in Britain unfortunately.
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. Juglans nigra is native to North America, from Massachusetts
and southern Ontario to Nebraska, south to Texas, and east to Georgia. |
| Height |
Black
walnut is a large deciduous tree reaching heights of 70-100 ft (21-30 m)
or more. This is a vigorous, spreading tree which can develop a trunk 2-4
ft (0.6-1.2 m) in diameter, and a crown spread of 70 ft (21 m). |
| Habitat |
It grows best on deep, moist and fertile soils, such as occur along river
bottoms. |
| Characteristics |
It has scented flowers from May to June, and the seeds ripen in October
In forest stands, black walnut usually has a long, clear bole and a small,
open crown. When grown out in the open, however, it has a short trunk and
a massive spreading crown. Black walnut has large, aromatic, compound leaves,
1-2 ft (30-60 cm) long. It bears rather large oval corrugated nuts that
are encased in a thick, fleshy yellow-green hull. In forest stands, black
walnut usually has a long, clear bole and a small, open crown. When grown
out in the open, however, it has a short trunk and a massive spreading crown.
Black walnut has large, aromatic, compound leaves, 1-2 ft (30-60 cm) long.
It bears rather large oval corrugated nuts that are encased in a thick,
fleshy yellow-green hull. It is in flower from May to June, and the seeds
ripen in October. A very ornamental and fast growing plant, it is sometimes
cultivated in N. America for its edible seed. Whilst potential yields of
7.5 tonnes per hectare have been suggested, it is more feasible to expect
annual yields of around 2.5 tonnes per hectare. Good seed crops are usually
produced every other year, though some plants fruit well annually whilst
others produce god crops every third year. The average weight of a seed
from wild trees is about 17g, though there are many named varieties and
the weight of their seeds varies from 20 - 30g. There are breeding programmes
that are seeking to develop cultivars with thinner shells. |
| Edible
Uses |
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.
The kernel is hard to extract and the oil it contains quickly turns rancid.
The unripe fruits can be pickled. The seed is borne in solitary fruits or
in pairs and is 3 - 4cm in diameter. The nuts can leave a permanent stain
on clothing.
An edible oil is obtained from the seed. A sweet taste but it tends to go
rancid quickly. Used as a seasoning in bread, squash and other foods.
The tree yields a sweet sap that can be drunk or concentrated into syrup
or sugar. It is tapped in spring. |
| Medicinal
Uses |
|
| Other
Uses |
Black
walnut has many uses in the forest products trade, and is often recognized
as one of the most valuable of North American hardwoods. It is commonly
used for gun stocks, cabinetry, and the creation of both solid and veneered
furniture. Unfortunately, its extreme value has contributed to its extirpation
in many parts of its range where it was formerly common. The nuts are oily,
sweet and quite edible, used most commonly for baking and confections. This
large, spreading tree makes an excellent shade and specimen tree throughout
its range.
For sheer elegance, a mature, open grown black walnut trees massive form
and long green leaves cannot be surpassed. Its oily nuts possess a distinctive
flavour that makes its English relative pale by comparison. |
| Propagation |
Seeds
should be planted in a seed bed as soon as ripe. Named cultivars are grafted
onto seedlings. 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. |
| Cultivars |
This
species hybridizes with J. regia, some named cultivars have been developed
from this cross for their seed. |
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