—It is certain that the air in the California raisin districts is much drier than that of the Spanish or Mediterranean districts generally. The night air is, in these districts, loaded with moisture, and dew is heavy and frequent, even in the middle of the summer. The air in Malaga and Smyrna feels quite moist, and without this moisture in the air the vines would grow less and require irrigation. In these places the raisin grapes grow on the steep hillsides without irrigation, but in California this could not be done anywhere except in El Cajon or in other parts of the San Diego district, where the air is considerably moister than elsewhere. This increased moisture is partly caused by the increased rainfall in these districts, and partly by their nearness to the sea and fogs. This moisture in the air will, when other conditions are equal, greatly benefit the grapes, causing them to grow larger, and the thickness of the skin is materially diminished. Combined with this moisture in the air, fogs are injurious or indifferent. There is always a great difference between warm fogs and cold fogs, and now I speak principally of fogs from the ocean. Warm fogs are not particularly injurious to the grapes, generally indifferent and sometimes even considerable of a benefit to the proper development of the grapes. In Malaga, San Diego and in Chile the Muscat grapes grow and thrive actually within the reach of the spray of the waves, and fogs are there not uncommon, but they are warm. It would seem that such a climate would cause mildew or oidium, but I cannot find that these fungi are particularly frequent in San Diego county, while in Malaga they are but little more common than in the inland districts of our State. But as we go north the cold fogs become more common, and the vines thrive less under their influence. North of Los Angeles county the Muscat vines do not enjoy the coast air, while even in Orange county the interior vineyards are preferred to those closer to the coast. But anywhere, even in the best situated districts, protection from the direct influence of the sea fogs is appreciated, and the best localities are those in which low hills afford this protection by modifying and increasing the temperature of the fog or sea air.
In Central, and in the larger part of Southern, California, the inland valleys are the most successful raisin-producing districts, while even in San Diego county, where the Muscats seem to thrive at the very seashore, the interior valleys alone afford the necessary heat and dry air for curing the grapes and transforming them into raisins. According to Consul G. H. Heap of Constantinople, the positions preferred for vineyards in Turkey are the slopes of elevated and sheltered undulating lands, or on the sunny hills that do not lie too near the coast, or are naturally protected from the cold winds and fogs of the sea. The Island of Cos or Zea is called the paradise of the Sultana grape, because Nature has given the cultivable land there the best possible protection from the direct influence of the fogs. In Malaga, according to Consul Marston, eighty per cent of the vineyards are situated on the hills and inland, ten per cent on the valley lands or plains, and ten per cent on the coast. With the exception of some of the San Diego vineyards, California cannot show any raisin vineyards as close to the coast as those found in Malaga. The main El Cajon vineyards are from ten to fifteen miles inland, while the former Santa Ana vineyards were situated from eight to twelve miles from the coast. The San Bernardino raisin vineyards are from twenty to thirty miles inland, while in the San Joaquin valley the raisin districts are more than a hundred miles from the coast, while the sea wind, before it reaches any of the vines, has been modified by passing over from two to three hundred miles of dry country.
Ideal Conditions of Climate.
—There remains only to draw some conclusions from the above facts. We are often asked what are the ideal conditions, as far as climate is concerned, for the proper development of the raisin grape, and for the proper curing of the raisins. Could we select such an ideal spot, where all the requirements for the raisin industry could be found in their highest perfection, with as few of the drawbacks as possible, our choice would be as follows: A moderately dry air, a frostless spring, a rainy winter and a rainless autumn. The temperature in the summer should vary between ninety and one hundred degrees, the fall months should now and then be visited by drying winds, while the winter frosts should be heavy and regular, but not below twelve degrees. Some have suggested that absolute freedom from any rain would be very desirable, as then no interference would be experienced with the cultivation of the grapes, but I doubt if the soil in such districts would not be rapidly exhausted through the want of weeds, the plowing under of which enriches the ground and enables it better to preserve the moisture provided for it by irrigation.
SOILS.
General Remarks.
—No one certain variety of soil can be said to be the best for raisin purposes, and both in different countries, as well as in the same district, various varieties of soils are valued equally. Every raisin district has, however, its favorite soil, which is supposed to have some peculiar advantages for the raisin grapes, but upon closer investigation we generally find other varieties of soils which are not inferior. Growers who have succeeded with raisin grapes on one variety of soil are only too apt to consider this kind preferable to any other. This is especially the case in California, where soils vary so much and where in some districts it is difficult to find forty acres with a uniform soil. Whether the soil is black, red or gray, it makes but very little difference, as long as it is rich and susceptible of the highest state of cultivation and has the faculty of retaining moisture. The deeper and richer the soil the better the Muscatel grape will thrive and produce, and as such soils are most generally found along the banks of creeks and rivers, or in their bottoms and sinks, we might conclude that in such localities the best soils for the Muscat grape may be found. Other varieties of raisin grapes, such as the Malaga (California) and the Sultana, do well in less rich soil; indeed, they bear profitably in places where the Muscat would be a failure. It is therefore important for every vineyardist to carefully select his soil and then plant on it the proper variety of vine.
Malaga.
—The soils of Malaga are of various kinds. The best is a reddish loam containing much gravel, both coarse and fine. This soil is very stiff and hard, and when dry is as solid as a brick. The red color is derived from oxide of iron or other iron compounds, which many of the best vineyardists consider a most desirable element in any raisin soil. The upland vineyards, or those on the slope of the hills, contain soils of decomposed clay and slate mixed with more or less gravel and sand. The Dehesa lands contain alluvial deposits of a black or gray color.