THE CULTIVATION OF HEMP
The botanical or scientific name for hemp is _Cannabis Sativa_, order,
_Moraceoe_, sub-order, _Cannaboidae_. The plant grows wild in Central
Asia, but is cultivated in many tropical and temperate regions of both
hemispheres. From a cordage point of view the fibre is, naturally, of
most importance, but, incidentally, it might be mentioned that the seed
is used as a food for birds, and oil is extracted from it; in addition,
in tropical countries, a resinous juice exudes from the stalks, leaves
and flowers which is made into a violent intoxicant.
The plants in general attain a height of from 4 to 8 ft. or more, and in
exceptional cases, such as under good cultivation in suitable soil,
approach 20 ft. in height. The leaves are five to nine lobed with
serrate margin. The plants are dioecious and the flowers are
yellowish-green, small and inconspicuous; the male flowers are numerous
and produced in drooping panicles, each flower of five segments; the
female flowers are fewer in number, on spikes, single leaf, single
ovary, with greyish-green to brownish-grey seed, and rich in oil. The
matured stems are usually hollow, and the bark layer very fibrous
throughout the whole length of the stem.
The plant readily adapts itself to great changes of climate, and, as
already stated, is found in all climates, from the tropical ones of
India and China to the frozen regions of Northern Russia. It is
adversely affected, however, in the earlier stages of its growth by
frost, and always requires a moderately strong sunny period during its
growth. It is cultivated in the temperate climates chiefly for its
valuable fibre, but a serviceable fibre may be obtained from the plants
which are grown in tropical countries.
The most important fibre-producing areas are Russia, Italy and
Austria-Hungary, but it is produced in other countries, notably those
mentioned below, as well as in Turkey, China and the Southern and
Western areas of the United States of America. The Italian fibre is the
best of all for fine work, while the Russian fibre, which has a special
affinity for tar, is the most satisfactory for use in the manufacture of
heavy cordage for maritime purposes.
The approximate annual production of hemp from fourteen different
countries appears below--
Russia 400,000 tons
Italy 80,000 „
Hungary 50,000 „
India 36,000 „
Siberia 22,000 „
Austria 18,000 „
France 15,000 „
Japan 8,000 „
Serbia 8,000 „
Caucasus 5,000 „
Poland 4,000 „
Bulgaria 2,000 „
Germany 2,000 „
Roumania 1,500 „
The successful cultivation of hemp requires a rich, deep and well-worked
soil with a large amount of humus. Alluvial soils are well adapted for
the purpose. The strong loam soils of Italy are typical of the best. In
all cases a good supply of moisture is necessary, otherwise the crop
would be short and stubby and ill adapted for the production of fibre.
The land should be well prepared by deep ploughing, and followed by
rolling and harrowing to produce a level and uniform seed bed. The roots
of the plants will penetrate into the subsoil if the land is well
ploughed, but waterlogged land is unsuitable. A liberal supply of manure
is essential owing to the vigorous growth of the crop, and while
farmyard manures are the best, the stalks of a leguminous crop may be
ploughed in. Manure from animal slaughter-houses is very suitable, and
all refuse from the previous hemp crop should be returned to the land.
Since the hemp fibre contains a large amount of lime and phosphates, it
may sometimes prove advantageous to use dressings which contain these
substances.
The seed should be selected with care, and should be tested for its
powers of germination. Stored seeds are liable to heat and lose their
vitality, and immature seeds are also unsatisfactory. Indian and Chinese
seeds are often mixed with home seed. In temperate climates sowing
should take place as early in spring as possible, but after the night
frosts have passed. The early spring rain and sun are very beneficial,
and the foliage which appears moderately early helps to conserve the
moisture in the soil as the heat of the sun gets more intense.
The amount of seed to be sown depends upon the type of fibre desired;
thus, one bushel of seed per acre for coarse fibre to three bushels per
acre for fine fibre are the approximate quantities, and the seed may be
sown broadcast by hand, or by machines into drills about 6 or 7 in.
apart. In all cases the seed should be well covered to prevent ravages
by birds, hence, it is usual after sowing to harrow and roll the fields
again for the above purpose, as well as to prepare a level and uniform
bed for the germination of the seeds.
Where the land is cultivated with the production of seed as its main
object, the seeds should be sown thinly and wide apart, say, in drills
or rows from 6 to 7 ft. apart, so that the plants will branch
extensively and thus provide facilities for a profusion of flowers. The
male plants are pulled after the bloom is shed, but the female plants
are allowed to mature under the best conditions so that a large crop may
result. Great care must be taken in harvesting and in storing the seed;
provision must be made to prevent the deterioration of seed through a
process of heating. The average yield of seed per acre is about thirty
bushels, but in exceptional cases as many as sixty bushels may be
obtained.
Under satisfactory conditions the young plants should appear in from
seven to twelve days, after which it is necessary to thin them out and
to remove the weeds. While the plants must be wide enough apart to
facilitate good growth, there should not be too much space between them
when grown for fibre, or branching out will result. If a field has
become troublesome with weeds, no crop will eliminate them as quickly as
that of hemp.
If desired both male and female plants may be harvested at the same
time, but it is often considered advisable to harvest them separately.
It is as well to make most of the mixed crop if the labour is available.
The male plants may be cut or pulled when the flowers attain maturity or
a little after, and when the leaves are changing colour from green to
brown. The female plants being shorter may be allowed to remain for
about four weeks when the seeds are beginning to ripen.
The yield of fibre per acre of land cultivated is influenced by several
conditions, but on good lands under satisfactory conditions of
cultivation, an average of 6 to 7 cwt. may be relied upon, and in many
cases this quantity is easily exceeded.
After the plants are harvested, a number of minor operations take place
in different districts before the plants are subjected to the important
process of “retting” or rotting. These preliminary operations are mostly
to reduce the weight of the plants and to discard undesirable matter
which happens to be easily detached, as well as to secure uniformity.
Thus, the tops and roots may be cut off, and the leaves stripped or
beaten off, while after the plants have been dried, they may be arranged
according to length and thickness. They are then tied up into bundles of
suitable bulk for the operation of retting.