_Limits of the Raisin Districts._--It is an interesting fact, and by no
means a coincidence, that the raisin districts of the world are found on
or between the same latitudes. Thus we find the California districts
between latitudes 32°, 75´ and 38°, 75´. The latitude of Smyrna is 38°,
28´, 7´´, that of Malaga in Spain 36°, 75´, Valencia 39°, 25´, Denia
38°, 50´, the Grecian Islands and Morea 37° and 38°, and finally Huasco
in Chile 28° south latitude. That the latter place is situated so much
farther south or so much nearer the equator cannot exactly be considered
exceptional, as it conforms with the general characteristics of the
Southern hemispheres as compared with those on the northern half of the
globe. In Europe the Muscat grape for raisin purposes is not a success
north of the fortieth degree of latitude. While the limits in California
and Chile are not yet fully ascertained, it may be presumed that, as far
as regards this country, these limits will not differ very much from
those of Spain and Asia Minor. Only years if not centuries of experience
will finally decide where and where not raisin grapes can be grown and
cured to perfection. While the vines and the grapes can be grown in many
places, the proper curing of the raisins is attended with more or less
difficulty in the various districts. With proper modes of curing the
grapes, and by protecting them from the inclemencies of the weather, the
limits of the successful raisin districts may be extended considerably
both north and south.
_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. 41½, 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.
_Frosts in Spring and Winter._--One of the frequent effects of spring
showers is spring frosts. They are always injurious to the tender Muscat
vine, and if occurring more than once during the same spring may
entirely ruin the crop. In California such frosts occur sometimes in
April, and observations inform us that they are most to be feared
between the tenth and fifteenth of that month, while sometimes they come
even later. The young buds are then either opening or fully developed
into shoots, which the lightest frost will blacken and cause to dry up.
Where the vines are irrigated and strong, one such frost may not ruin
the crop, as new buds will start out in place of the old ones destroyed,
and new shoots and new blossoms will come out. I have seen as many as
three such crops of shoots develop from the winter buds, but each
succeeding crop of such shoots is weaker than the preceding one, and
bears less and later grapes. Happily, these frosts occur but very seldom
in the Central and Southern California raisin districts, and during
fifteen years of observation I have seen only three such frost years in
which the branches were partially injured. In neither of these seasons
was the crop materially injured as to quantity, the principal effect of
the frost being a retarding of the crop for a week or more. Smoking of
vineyards can only be successfully carried out in small valleys
sheltered from heavy winds, but on the open plains such smoking is
accompanied with difficulties, and its effect is uncertain. The growing
of a limited number of windbreaks has in the Fresno district no doubt
modified the climate, and made spring frosts rarer and less to be
feared.
While the spring frosts are injurious to the grapes, winter frosts are
on the other hand most beneficial, if not necessary to a continued
raisin cult. The raisin grape must have a season of recuperation, and
winter frost is the only climatic phenomenon which, without injury to
the vine, can procure it that rest which is so necessary for all
deciduous trees, by nature destined to enjoy alternate periods of growth
and sleep. The absence of frost causes the sap of the vine to circulate
more or less in the wood, and the vine never ceases to grow. This is one
of the reasons why our deciduous vines do not succeed well in the
tropics, where there are no cold seasons to cause the leaves to fall and
the sap to become dormant. In the tropics, therefore, our deciduous
vines keep on growing, set little or no fruit, and prove unprofitable.
This phenomenon is shared there with other trees, and peaches, pears and
apples act in the same manner. They all appear to need the rest afforded
them by the winter frosts. It is also a question of very great
importance, whether the continued and unnatural activity of the vine, at
a time when it should be dormant, does not invite diseases of various
kinds, which find the exhausted vines unfit to withstand their ravages.
It may be possible that _mal nero_, the vine plague and other similar
and as yet insufficiently understood diseases, are especially
destructive to vines growing in frost-free climates, while in colder
climates they make but little headway, the vines as it were being
protected by the heavy frosts, which either kill the enemies of the vine
or enable the latter to gather the necessary strength to battle with
them through the growing season. There can be little doubt that at
present the healthiest vineyards are those growing in countries where
winter frosts are severe, but on the other hand we know that grapevines
have been growing for ages in temperate climates, where the frosts, even
if not entirely unknown, are still of very rare occurrence.
_Summer Temperature_.--The temperature in summer time must be sufficient
to properly ripen the grapes, but must not be so great as to injure them
either while they hang on the vines, or while they are exposed to dry on
the trays. The average heat required to do the work of maturing is not
exactly known, but it is certain that a very high degree is not
absolutely needed to produce sweet grapes. As far as our experience
goes, it seems that cool weather, with the average temperature of ninety
degrees Fahrenheit, would be most beneficial in the fore part of the
season, while when the grapes begin to ripen a greater heat is
desirable. It is not the warmest countries nor the warmest seasons which
produce the earliest grapes. Thus while the season of 1888 was in
California unusually cool, with the thermometer seldom reaching one
hundred degrees in June and July, the raisin season was nevertheless a
very early one, and much earlier than seasons remarkable for their early
high temperature. In Malaga and Smyrna, the heat seldom reaches one
hundred degrees, and the grapes ripen several weeks earlier than in
Fresno, where the summer temperature averages ten degrees higher. In
Fresno, on the contrary, the season is earlier than in Southern
California, where probably the seabreezes retard the ripening of the
grapes. A temperature of over one hundred and five degrees proves
injurious to unprotected or exposed grapes in the central region of
California, but in San Diego county several degrees less is sufficient
to scald the grapes or give them a cooked flavor if they are already
exposed on the trays to dry. It is certain that with an average highest
temperature of ninety degrees, the grapes develop better and become
larger and sweeter than where the heat is excessive and reaches one
hundred and ten degrees or more.[6]
[6] Whenever the temperature is referred to it means the degree of
heat (Fahrenheit) in the shade, and not in the sun except when so
expressly stated.
The time when the greatest temperature occurs is of practical
importance. Excessive heat can be tolerated by grapes protected by
leaves and branches or otherwise sheltered, but if it happens at a time
when the bunches are exposed to dry on the trays, the injury to the
berries will be great or even ruinous. Early localities are especially
apt to suffer in this way, and it is well to experiment before too much
confidence is placed in very early regions. To such places, however,
there remains the possibility of curing the raisins in partial shade, as
is done in Chile, thus producing raisins of an entirely different type
from the Malaga or California product.
_Winds, Injurious or Beneficial._--In the California raisin districts
hot, electrical winds are much feared in the months of June and July, or
before the grapes have begun to ripen. In the San Joaquin valley these
winds come from the northwest and sweep down over the vines, often
scorching the leaves and frequently drying the berries on the exposed
side. In the course of a few days the berries dry up entirely, and the
whole bunch is lost. These drying winds are not peculiar to any certain
part of California, but occur from time to time in every raisin district
on the coast, in the south as well as in the center, on the coast as
well as inland. The remedy is to grow the vines low and to keep the
berries well covered. The planting of windbreaks will also modify these
winds, and in places where they formerly were common they have now
entirely ceased or become so modified that they cause no injury to the
grapes, but prove even beneficial on account of the quicker and better
maturing of the fruit. In certain districts, especially in San
Bernardino and in Orange, some very drying winds are experienced late in
the season,--in September and October. For the raisin-growers these
winds are a blessing. They quickly dry the exposed grapes, which have
been retarded in drying, or perhaps even injured by a previous shower of
rain or by continued heavy dews. These winds are undoubtedly desert
winds, and similar to the Terral of Malaga, which, sweeping over the
inland plains of La Mancha, reach the coast vineyards and quickly mature
the grapes. In Malaga there is also a moist southern wind, the Levante,
which retards the ripening and the curing of the grapes, and which must
be considered as our southwesterly fall winds, which, saturated with
moisture, swell the overdried raisins as well as prevent the yet green
grapes from drying. They are precursors of the rainy season, and warn
the grower to prepare his dryer if he possess one. In Greece and Smyrna
such hot or moist winds are also known and feared, and cause at times
much damage in one way or another. We might here also mention the cold
“northers” which are common in the California raisin districts in
springtime, and which sometimes both cause the young shoots to break off
from the old wood and make it easy for the mildew to attack the flowers
or the young berries of the vines. Against these northwest winds we have
two remedies, summer pruning and sulphuring, which, if applied in time,
are both quite effective.
_Fogs and Moisture in the Air._--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.