HOP, CULTIVATION OF THE. There are two species commercially grown, Humulus Lupulus, a native of Europe and Asia, and Humulus americanus, a native of America. The culti vation of the Old World hop probably originated in Asia, whence it gradually extended westward through Europe to England and subsequently to America. The American hop is grown chiefly in the Pacific States. In all countries where the hop is cultivated the crop is localized in fairly well defined areas; this is due, to some extent to climate but also largely to the fact that many of the operations involved are very specialized and require experi enced labour, which can be obtained only in districts where the workmen have lived among hops all their lives.
Hops are grown in Austria, Bavaria, Belgium, Czechoslovakia, England, France, Germany, Hungary, Jugoslavia, Poland, Ru mania, Russia, Canada, the United States of America, Australia and New Zealand. Germany has the largest area of land under hops but England produces the greatest weight of hops, fol lowed closely by the United States of America ; the hops of the latter countries being pollinated develop larger cones and there fore a higher crop per acre.
The plant is somewhat sensitive to climatic conditions, and even the comparatively small differences in these in different hopgrowing districts are sufficient to determine the variety of hop which will thrive most satisfactorily. The mean summer temperature should be about 6o° F and the district should not be subject to strong winds during the growing and ripening periods. The rainfall should be abundant during the growing period and light during the ripening period.
The most suitable soil for hop growing is a fairly heavy loam overlying a pervious subsoil, such as gravel or chalk ; it must be deep enough to enable the roots to penetrate to a level where moisture is always available; this moisture however must not be stagnant—hops cannot tolerate a badly drained soil.
Hops are propagated vegetatively by means of cuttings (con sisting of the basal portions of the previous year's bines) taken in the spring ; they are grown in nursery beds for the first year and are then known as "bedded setts." These are exactly like the parent plants and the variety is thus kept true to type.
Planting.—Bef ore planting hops the land is prepared by deep ploughing and loosening the subsoil with a subsoil plough ; then, in early spring, the ground is set out with small sticks to indicate the positions of the "hills" or places where the hops are planted. (This term is derived from the old custom of growing hops on small mounds of earth.) These are commonly placed six or six and a half feet apart each way, the width of planting being governed by the vigour of the variety and the fertility of the soil. The setting out is carried out with great care as it is essen tial that the rows be perfectly straight and the hills exactly the correct distance apart, in order that they may be in the right positions relative to the overhead wire-work which supports the strings up which the bines climb. Having set out the ground and obtained "setts" of a suitable variety, planting is commenced at the first spell of fine weather in January or February. In England one male plant is provided for each 200 female plants, as it has been found that fertilized cones develop more rapidly and grow larger than unfertilized cones; in Germany and other mid European hop growing districts however the male is rigorously excluded and seedless hops are produced. Holes about nine inches square are dug, a little farmyard manure or shoddy mixed with the soil in the bottom and, usually, two setts with the old bines trimmed off placed in the hole with the crowns close to the stick and just below soil level. The hole is then filled in and the stick pulled over at a slant to indicate that the setts have been planted.
During the dormant period the hops are "dressed." The soil is scraped away with a hoe so that the crown of the plant is exposed. The bases of the previous season's bines are then cut off close to the rootstock and any underground runners that may have been produced are removed. The object of this operation is to restrict the number of shoots, to keep the rootstock below soil level and to prevent the plant from spreading into the alleys. When "dressing" has been completed the coconut fibre string (coir yarn) is put up.
Growth commences in April and by the end of the month or the beginning of May the young bines will be i or eft. long. Each hill produces more shoots than will be required to furnish the strings ; it has been found that those of medium strength are the most fruitful and two of these are trained up each string; the remainder are pulled off. As growth continues it is necessary to go through the hops from time to time and replace any bines that may have fallen away from the strings.
In the autumn the land is ploughed in such manner that the rows of hills are situated on the ridges and the open furrows run along the middle of the alleys ; this throws the excess water from heavy rains away from the hills and allows them to lie in a drier condition during the winter. In the spring the land is again ploughed ; this time the furrow slices are thrown in the opposite direction, forming the ridge in the middle of the alley and leaving the rows of hops on narrow unploughed strips of land. When "dressing" has been completed these strips are dug by hand. The succeeding cultivation consists in working the ground with culti vators to produce a good tilth and to keep down weeds, the depth being gradually decreased as the season progresses until the hops are in "burr," when cultivation is either discontinued or carried out very shallow to keep weeds in check. The ground close to the hills is hand hoed periodically.
Another serious fungous disease is the Hop Mould (Sphaero theca Humuli [D.C.] Burr.). This fungus produces white pow dery patches of spores on the leaves ; if the "burr" becomes in fected its growth will be arrested and it will remain in the form of a small knob covered with the white fungus. When fully grown cones are attacked they become foxy-red in colour (Red Mould) and dark brown bodies—the winter stage of the f ungus are found on the cone. The remedy for this disease is dusting the plants with finely divided sulphur.
The Mosaic disease, caused by a virus, gives considerable trouble with some vaneties ; the shoots become brittle and stunted, the margins of the leaves turn backward and their colour becomes mottled with light patches; the affected plants produce very few cones and are killed in a season or two. The plants suffering from this disease must be dug up and burned as soon as it is recognized. A similar disease, called "Nettlehead," occurs principally on the variety "Fuggles." The most important insect enemy of the hop is the Hop Aphis (Pliorodon humuli, Schrank.). The eggs of this insect are laid on damson, plum and similar trees in the autumn and hatch out in April; from May to mid-June winged aphides fly to the hop where they produce wingless progeny which increase with great rapidity. In September another generation of winged aphides is produced which migrate to the damson trees. The aphides weaken the hop by extracting its sap as food; they also excrete a sticky substance ("Honeydew") which covers the leaves and blocks their pores. Upon this "Honeydew" a black fungus grows which gives the plant a sooty appearance. - If the insects invade the cones the black fungus follows and the value of the crop is con siderably reduced. The remedy for this pest is to wash the plants with a soapy solution of nicotine, or other insecticide, using a powerful spray.
Other important animal enemies are wireworms (the larvae of click beetles), which damage the young shoots below ground level, and red spiders (Tetranyclius altheae, v. Haust.), which at tack the leaves, particularly in dry weather.
The hops are picked into baskets, of five or six bushels capacity, or bins of loose sacking suspended on a light wooden framework. The pickers are organized into companies of six to ten baskets or bins, each company being in charge of a "binman" who is respon sible for the work of the company. The price paid for picking varies from 2d. to 3d. a bushel according to the nature of the crop.
The hops are taken from the garden in loosely woven bags ("green bags" or "pokes"), holding ten bushels, to the kilns where they are dried as soon as possible after picking. In Kent the buildings containing the kilns are known as oast houses. The common kiln is built of brick, the wall being either circular or square, 18 or 20f t. in diameter or side and about i 6f t. in height. From this a tiled roof, sealed inside with lath and plaster, extends in conical or pyramidal shape a further 18 to 24 feet. The roof terminates in an opening about aft. in diameter surmounted by a wooden cowl pivoted and provided with a vane, so that its opening is always away from the wind. An open batten floor is fixed in the kiln about i 4f t. from ground level and upon this is laid a loosely woven horsehair cloth. In the lower part an open fire of anthracite burns in a brick fireplace. The hops are placed on the horsehair cloth ("hair") to a depth of 8 to i6in. and are dried by the hot air and products of combustion which pass through them from the fire.
The operation of the kiln requires very skilful management ; a mistake in drying may reduce the commercial value of the hops enormously. Great care is necessary in the control of tem perature; a thermometer is fitted below the "hair" floor to guide the dryer. At first the temperature is kept comparatively low, rising gradually from about i oo° F at the time of loading to about 15o° F at the end of four hours and reaching the maximum of 16o° F at the end of the sixth hour. The rate at which the temperature is allowed to rise is, however, intimately connected with the strength of the draught. Nine or ten hours are gener ally required to dry a load.
The hops when dry are removed from the kiln, care being taken not to break the cones (which are then in a brittle condition) as breakage causes the loss of lupulin—the valuable part of the hop. They are allowed to remain exposed to the air for a few hours during which the residual moisture becomes more evenly distributed and some moisture is absorbed from the atmosphere. In America the hops are allowed to remain in this state for some weeks before being baled, but in England they are pressed into "pockets" (large bags made of stout jute sacking about 6ft. in length and 2 f t. diameter) after four or five hours' exposure. Each pocket contains just over 12cwt. of hops and is marked with a serial number, the name of the grower, parish, district and year of growth.
The pockets are sent by the grower to a hop factor who cuts a sample of about 'lb. from each pocket and by these samples sells the hops to hop merchants who, in turn, sell them to brewers.
For further information on the cultivation of hops, see "Cultivation, Diseases and Insect Pests of the Hop Crop" (Ministry of Agriculture and Fisheries) and the articles on "Hops" and "Diseases of Hops" in vol. iv., Farm Crops (The Gresham Publishing Company Ltd.) .
(A_ H R 1 The growing of hops in the United States started in Virginia about 1648. Thereafter the industry shifted to New York and Wisconsin, and then to the Pacific coast, which now produces practically all the hops grown in the United States.
On the Pacific coast, hop farms are always called hop ranches and are located alongside or very close to rivers because of their need of an abundant water supply. At the same time, lands for hop growing must be well drained, as hops are easily drowned. Hops require exceptionally rich and deep soil, the roots often going to a depth of 20 feet.
Nearly all hops on the Pacific coast are grown on the high wire trellis system, which runs between 14 and 20 ft. from the ground level.
The spraying and dusting of hop vines with insecticides against hop aphis, red spider, and downy mildew are of substantial help if it is efficiently done throughout the hop growing season, but the expense of such spraying is too large a factor of cost for the hop growers to stand except when hops can be sold at prices well above 20 cents per pound to the grower. Hence when the pros pects are such that hops cannot be sold above that price, less spraying is done by the grower against those pests and the risk of loss or damage of the crop is greater. In some years the loss or damage of the hop crop in Oregon, western Washington and Sonoma county, Calif., by insufficient or inefficient spraying rep resents over 50% of the value of the crop.
During the past 15 years the consumption of hops within the United States, the export of hops from and the import of hops into the United States, and the prices of hops have been subject to violent changes.
National Prohibition reduced the consumption of hops from about 35,000,000lbs. in 1914 to about 6,000,000lbs. in 1920. For the year ending Sept. a, 1939 in round million pounds the United States production was 32, the imports 9, the consumption 3o, and the exports 4.
The controlling factors that determine the brewing value of the hops are its seedlessness, its freedom from leaves and stems, its aroma and its quantity of brewing soluble resins. In that respect the Pacific coast hops are far richer than any other hops grown in the world. It is not uncommon for Pacific coast hops to run as high as 2o% in resin content, nor is it uncommon for the best foreign hops to run as low as Pacific coast hops average about 3o to 4o% richer in brewing resins than English and Conti nental hops.
By far the largest hop farms in the world are on the Pacific coast. One of its farms has 65o ac. in hops, all grown on the high trellis system. This farm is only one of a number of hop ranches owned and operated by the same company which has grown a total of over 3,00o ac. of hops in various districts of the Pacific coast.
The portable machines pick the hops in the fields while the machines are travelling. The sacked hops are then hauled to the hop drying houses.
The theoretical capacity of a portable hop picker is 3 acres per so-hour day. The machines can work day and night, rain or shine.
This results in hops of the very highest quality both in aro matic oils and in soluble brewing resins. The method requires about six times the drying floor space that is necessitated by the usual hop kiln-drying system.
Large fan blowers are used to blow the air through the hops.
(E. C. H.)