The Raisin Industry / A practical treatise on the raisin grapes, their history, culture and curing

by Gustavus A. Eisen

Dry Seasons, Spring and Fall Rains.

—The climate of the Mediterranean basin, as well as of the raisin districts of the New World, present the peculiarity of having only two distinct seasons, one dry and warm, and one cold and wet. There are other parts of the world also characterized by a dry and a wet season, for instance Mexico and Central America, etc., but they differ in the important point, that whereas the climate of the raisin districts is dry during the growing or summer season, Mexico has then its greatest rainfall. While grape-growing may not be impossible under such circumstances, the curing and drying of raisins is impossible, except with the aid of costly and burdensome appliances, the expense of which will very much increase the cost of producing the raisins. The climate of the raisin centers is by no means uniform. As a rule, the farther north we go the less is the distinction between the dry and the wet season, the shorter is the former and the longer the season of rain. Experience shows that the less this distinction between the seasons is marked, and the shorter the rainless season, the less favorable is the climate for the raisin industry. The longer the dry season, and the less rain during the same, the more favorable is the locality for raisin drying and curing, supposing, of course, other necessary conditions are not absent. This absence of summer rains and cold fog is the most important climatic condition, and the one that more than any other decides upon the advantages of any certain locality for the industry under our consideration. A perusal of the reports from the different raisin districts will convince us of this. For California we need not refer to any special reports, as the newspapers are full of them every year from May to November, and it will suffice to state that any large amount of rain after the beginning of June, and especially in September, October and November, when the raisins are curing, is considered very detrimental, and sure to cause much loss. Heavy and continued rainfall during the drying season would not only injure the raisins, but might even totally ruin the crop. Any district where year after year such showers occur, would not be considered favorable for the raisin industry, and would no doubt be given up to something else. To show that these same conditions also exist in the Mediterranean raisin districts, we will here quote a few extracts from the United States consular reports from there. Consul W. E. Stevens, United States consul at Smyrna, writes:[5] “It happens occasionally that rain falls during the vintage time, causing heavy loss to growers through the inevitable deterioration in quality. This was the case last season (1883), and large quantities of raisins were in consequence shipped to France to be made into spirits.” From Valencia another consul writes: “In the event of wet and damp weather, the hurdles (or grape mats) are piled up in sheds covered with mats or painted canvas. Of course in this case the drying is retarded, the quality of the fruit deteriorates, and the expense and labor of curing are considerably increased.” Two years ago ten thousand tons were thus damaged in the Denia district. While the Mediterranean districts are comparatively rainless during the summer time, still they are far less so than California. The rainy and dry seasons there are less distinct than with us.

[5] Consular Reports, No. 41¹⁄₂, June, 1884, page 745.

Among the Grecian Islands, the production of currants is confined to only a few localities, principally on account of the untimely rainfall on the other islands. Dr. Davy (Ionian Islands, page 320) tells us: “The attempts to extend the culture of the currant to some other islands have been only partial, and attended with doubtful success. This, it is to be understood, is not owing, as has been asserted, to any unfitness of the soil on other islands, as it is analogous on them all, but rather to some difference of climate, especially about the times of ripening, gathering and drying of the fruit, consisting in greater liability to rain, a heavy fall of which is ruinous to the crop, and which, during the period of gathering in the currant islands, is considered a great calamity.” But even in Zante and Cephalonia in Greece, the crop is sometimes greatly injured on account of rain. Thus in 1857 a crop of fifty thousand tons was expected, but disastrous rains in August injured the raisin grapes to such an extent that seventeen thousand tons were totally destroyed, and twelve thousand tons became unfit for anything else than distilling. Malaga in Spain, which of all the districts most resembles California, has undergone similar experiences, both damaging and ruinous.

It is thus that the fall rains are everywhere feared the most, the more so where they may be expected with regularity, and where the district is so situated that the heat of the sun is not powerful enough to rapidly dry the injured crop. Thus in Valencia the rains are feared more than at Malaga. In the latter place the sun is powerful enough to dry the raisins, and only repeated showers would injure the crop. Our experience is very much the same, and the early fall rains in the northern part of the State are to be feared much more than rains at the same time farther south, where a few showers would soon be succeeded by warm weather, and a hot sun powerful enough to dry the partially cured grapes. On account of local conditions, certain parts of Central California are freer from these fall rains than the more southern districts, but this disadvantage is counteracted by the greater amount of warm weather and drying winds just at a time when they are most needed. But while the southern part of the State is in this respect not as favorably situated as some other parts, the disadvantage is greatly counteracted by the warmer and drier fall weather in October and November, and by drying winds which are often able to desiccate the moistened raisins in a very few days.

Spring rains in May or even in the early part of June cannot be considered greatly detrimental to the vines. On the contrary, if only occurring at long intervals, one or two showers say during the season, they are rather beneficial than otherwise. In California I have never known them to injure the crop, except if accompanied by heavy hail. Much alarm is regularly felt every time such a shower happens to come, but after it is well over it will generally be found that the vines look fresher and better, the ozone and ammonia which was brought down by the rain having acted as powerful fertilizers for the grape-leaves, and increased their vigor and growth. The only thing that might prove injurious at this or any other time of the growing season would be continued cloudy weather before or after such showers, which would cause mildew. Such weather has to my knowledge never been experienced. Occasionally spring rains also bring frost, and this of course is one of the greatest enemies of the raisin-vines.

Winter Rains.

—In order that the raisin grapes may develop and mature without the aid of irrigation, the winter rains should be sufficient to keep the soil moist during the dry months. The absolute quantity of rain thus necessary varies in different localities. In California, generally, we would say that from twenty to twenty-four inches of rain would be required every year to keep the soil sufficiently moist to grow Muscatel grapes without irrigation. The nearer we go to the coast the less rainfall is required to supply this moisture, and the farther we go inland, the more elevated the land, the less rain is needed. Thus a regular rainfall of twenty-four inches would possibly not suffice on the low plains of the San Joaquin valley, while in El Cajon in San Diego county one-half of this rainfall is enough to grow the vines and mature small crops of very good and superior grapes.

It matters not from where the moisture comes,—from rain, seepage, moist air or irrigation,—as long as it is not present in excess nor too scant. In El Cajon valley the moisture appears to be held in suspense in impervious strata, or perhaps in strata which contain and preserve the moisture as does a sponge. In parts of Chile, as well as in Malaga and Smyrna, the winter rainfall is sufficient to grow crops of fair size and good quality, but it is almost certain that judicious irrigation in any of these places proves beneficial and remunerative. Of all the present raisin districts, Smyrna enjoys the greatest rainfall, often as much as thirty odd inches of rain. Of localities which grow raisins profitably with the least possible amount of rain, and without irrigation, Huasco and El Cajon take the lead. In Central California, as well as in San Bernardino county, no raisin culture would be possible with the natural rainfall. In foreign countries, Valencia and the Grecian Islands, as well as Morea, are similarly situated in not having sufficient rainfall to produce paying crops.

As a rule it may be said that, where the rainfall is sufficient to grow the Muscats without irrigation and cause them to bear good crops, the fall rains are also too frequent and too injurious to the drying grapes to allow a profitable raisin cult. The proper amount of moisture necessary to perfect the grapes cannot be ascertained by the aid of the rain gauge. While, as we have said, from twenty to thirty inches may be enough in Smyrna, from seven to ten inches suffice in El Cajon, and in Chile even less is required. The proper amount of moisture can best be told by the state of growth of the vines. The vines must have moisture enough to be kept growing up to the very time of the maturity of the grapes. The proper sign of this is the green and fresh color of the young shoots or the tips, combined with a certain vigor of the tendrils. When the tips cease to grow, and the tendrils begin to dry up, then the moisture has begun to give out, and irrigation should have been resorted to; the winter rains were not sufficient.