The Olive Its Culture in Theory and Practice/Chapter 3

by Arthur Tappan Marvin

 

CLIMATE.

"Aut praefervidum aut gelidum statum coeli patitur."^[1]⁠

Columella

The olive requires a moderate climate, it cannot flourish in or endure extreme heat or great cold. Its zone of cultivation lies between forty-five and eighteen degrees north latitude, and a corresponding belt in the Southern Hemisphere, outside of either of these extremes the tree may possibly live, but will refuse to give any fruit. Indeed, south of eighteen degrees in north Africa it attains a luxurious growth, but only fruits where it enjoys the caressing breeze from the Mediterranean Sea. For successful cultivation the yearly mean temperatures should not be less than 57 degrees Fahrenheit. As to locality where olive culture is possible and practicable. Five hundred and eighty-eight feet of elevation represent one degree of latitude, so Colfax with an elevation of 2421 feet above the level of the sea and standing nearly on the thirty-ninth parallel of latitude must be debited with a little more than four degrees, which would bring it up to between forty three and forty four degrees, showing that Colfax and places of similar elevation and latitude nearly touch the northern limit of the olive in California. To cultivate it successfully further north a lower situation must be sought. Hence the further south the point of cultivation the greater may be the elevation. In the Sierra Nevada mountains, in Grenada, Spain, in latitude thirty-seven degrees, the olive flourishes at a height of three thousand feet. In Algiers, North Africa, in about latitude thirty-five in the Atlas range, it is found at a height of forty-eight hundred feet.

In Catania, Italy, it is successfully grown at an elevation of three thousand one hundred feet. The olive dearly loves a breeze, not simply air and ventilation but a veritable soft wind. This is therefore necessary to its well doing, especially at the flowering season. A still, intense heat may be fatal to the promise of a crop by burning off the blossoms; for this reason and also to escape humidity it forsakes the plain and seeks the middle hills. The olive avoids the arid tops of wind swept heights but its home is the half hill. Follow a line of olive trees up a steep and it will be noticeable that those nearest the top are found to be stunted and lacking soil about the roots, the earth having been carried down the slope by rains and the trees are visibly affected by their situation.

Within the olive zone there undoubtedly are many points where the tree will not thrive because it is exposed to too great cold which must be fatal to it—say anything below fourteen degrees—or, if the heat be too great it evaporates the sap and thus prevents nutrition.

To temper too warm a climate water seems to be resorted to. In the Island of Candia in the Mediterranean on the thirty-fourth parallel the olives fruit regularly when watered, if they receive no water it is quite doubtful if the flowers set or not. In Athens, Greece, if they are not irrigated their yield is very uncertain. In Africa—both in Morocco and Algiers—in order to secure a crop it becomes absolutely necessary to give them water. In Valencia and Murcia, Spain, it is the usual practice to water the olive, and indeed with a loose soil and dry climate the irrigated trees respond with the surest crop. But the soil, the climate and the exposure must be the guide and indicate the necessity. Owing to the extreme dryness of the California summer, it is possible it may become needful in certain localities to irrigate the orchard in order to insure a crop. To deal with sections where there are apt to be cold snaps, the only remedy is to chose those varieties more nearly resembling the wild type which are hardier and better able to resist low temperature. The smaller the tree and the closer to the ground it grows naturally, the more likely it is to be damaged by a frost. On the Quito farm the late cold weather^[2] did absolutely no harm although there were trees on the place of not more than three years of age, and the mercury touched sixteen degrees above zero. Even a higher temperature than this has been fatal to olive trees, but that has been the result of a sudden thawing after a cold night. Anything lower than fourteen degrees of cold is too chilling for the olive to endure; such weather not only will kill the leaves and branches, but even the wood itself will succumb. The olive is not so hardy as the grapevine, the latter requiring only ten thousand eight hundred degrees Fahrenheit to ripen its fruit, whereas the olive needs twelve thousand seven hundred degrees, although some varieties will ripen with ten thousand eight hundred degrees, from blossoming time to maturity, among which is the Spanish Manzanillo. To ascertain whether any particular locality in California is suitable for olive growing, first consult the thermometer. A mean temperature of sixty-one degrees Fahrenheit, from the first of March to the end of December inclusive, will be sufficient guarantee; or this same mean, from the beginning of the flowering period—say May twentieth to the end of December—will ripen the berries. Where the summer heat is greater the fruit will ripen earlier.

The olive begins to move in March at a temperature of fifty-two degrees, it buds at fifty-nine degrees and flowers at sixty-seven degrees. The blossoms set at a temperature of seventy-one degrees of heat, and to ripen the fruit a minimum of eighteen thousand five hundred degrees of heat is necessary, dating from the period in March when it first began to move. A good general rule to rely upon would be, that where one can obtain a mean temperature for spring of fifty-six degrees; for summer, of seventy degrees; for autumn, of fifty-eight degrees and in winter a minimum of twenty degrees the olive can always be successfully cultivated; bearing in mind, however, that some varieties require more heat than others and that peculiarities in the atmosphere or the soil may make it impossible to grow the olive even with this temperature. To obtain the mean temperature with the necessary exactitude requires careful observation at least three times a day, and a minimum thermometer to show the lowest temperatures during the night and early morning is imperative. A recent invention, however, has simplified this labor very much; it is known as Drapers' Recording Thermometer, and consists of a dial, driven by clock work, which makes a complete revolution in one week and as it revolves under a pen attached to the thermometer proper a curved line in red ink is drawn on the face of the dial, which shows by lines thereon the exact temperature of the air at every hour during the day and night. The only attention this machine requires is to change the dial once a week, to wind the clock at the same time, and to feed the pen with a few drops of prepared ink. The weekly record dial is then filed away, and thus with very little trouble the most exact data is obtained for the guidance of the orchardist.

The following tables are intended to show the latitude and degrees of heat required for ripening the olive. In Spain it will be noticed that the temperature averages very high, with the usual result of producing rather too gross an oil.

	Elevation.	Latitude.	Mean Temperature.
Seville	300	37.20	68
Jaen	――――	37.45	64
Valencia	Seaport	39.20	63
Granada	――――	37.15	61
Murcia	――――	37.55	66
Alicante	66	38.20	67
Badajoz	――――	38.40	63
Barcelona	Seaport	41.15	63
Cuidad Real	――――	39.00	62
Saragossa	613	41.40	60
Palma	――――	39.30	67
Cadiz	Seaport	36.30	66
Madrid	1916	40.30	58

The data from Italy is much more exact, as seen in the following tables on pages 41 and 42. These may be constructed for any locality in California by first ascertaining the mean temperature each month and multiplying it by the number of days in said month. It will be noticed that the temperature of San Jose very nearly approaches that of Florence.

PLACE	Catania		Calabria		Syracuse		Palermo		Naples		Ancona		Genoa		Pisa		San Reno		Rome
Latitude	37°	28'	38°	31'	37°	3'	38°	7'	40°	52'	43°	37'	44°	23'	48°	43'	43°	50'	41°	33'
Altitude	31°	20'	23°	00'	12°	00'	22°	00'	37°	00'	30°	00'	48°	00'	8°	00'	20°	00'	49°	00'
March	56	1,736	54	1,664	56	1,736	56	1,736	54	1,664	50	1,550	52	1,612	52	1,612	52	1,612	50	1,550
April	60	1,800	59	1,680	60	1,800	60	1,800	60	1,800	58	1,740	58	1,740	60	1,800	57	1,710	55	1,650
May	68	2,108	66	2,046	66	2,046	65	2,015	68	2,108	67	2,077	65	2,015	65	2,015	63	1,953	65	2,015
June	76	2,280	72	2,160	74	2,220	72	2,160	74	2,220	74	2,220	69	2,070	71	2,130	69	2,070	71	2,130
July	81	2,511	80	2,480	79	2,449	78	2,418	78	2,418	80	2,480	77	2,387	77	2,287	75	2,325	77	2,387
August	82	2,542	80	2,480	79	2,449	78	2,418	78	2,387	77	2,287	75	2,325	75	2,325	74	2,294	74	2,294
September	77	2,310	77	2,310	75	2,250	74	2,220	74	2,220	72	2,160	72	2,160	72	2,160	70	2,100	70	2,100
October	68	2,108	68	2,108	69	2,139	67	2,077	66	2,046	62	1,922	64	1,984	62	1982	62	1,982	62	1,922
November	60	1,800	62	1,860	60	1,800	60	1,800	56	1,680	52	1530	53	1590	52	1560	53	1590	51	1530

Wherever eighteen thousand five hundred degrees can be accumulated before frost the olive will ripen, so that if this number of degrees is shown by October in any certain locality, then the olive will ripen there in that month; but in others, where frost intervenes, the olives must be left hanging on the trees for a longer period. This, however, should not extend beyond the end of February, as a later date than this is prejudicial to the welfare of the trees. The lesson derived from these tables seems to be that where the sum total of degrees for the year does not reach twenty-one thousand degrees Fahrenheit, the olive fails to ripen; this we see in the following table, is the case in Sienna, Benevento, Perugia, Bologna, Milan and Turin, and also that this is the fact where the temperature falls below fifty in November. Whether this will prove to be as true in California as in Italy experience alone can determine.

The following table on page 44 is presented in centigrade degrees, as in Fahrenheit it would fail to indicate the object intended, which is the exact period when the olive ripens. The reason of this is, that in Fahrenheit thirty-two degrees of cold are always included which are unnecessary and confusing in deciding the period when the olive ripens, as only degrees of heat are needed. This period is reckoned beginning from the first of June up to such a date as shall give three thousand nine hundred and eighty-two degrees of heat, which is the amount necessary to ripen the olive. As soon as this number of degrees is reached, even though it be the first of October, there the olive will ripen at that time. To change a daily or average temperature Fahrenheit to Centigrade subtract 32° and divide by 1.8, the result will be Centigrade degrees; thus 52° Fahrenheit—52°-32°/1.8=11.11° Centigrade.

To change Centigrade to Fahrenheit multiply degrees of Centigrade by 1.8 add 32° and the result will be degrees Fahrenheit. Thus 20° Centigrade 20x1.8+32=68° Fahrenheit.

The following incomplete list of cities and towns in California and vicinity shows by their temperature that with few exceptions the olive will flourish throughout the length and breadth of the State.

TABLE OF MAXIMUM, MINIMUM AND MEAN ANNUAL TEMPERATURE, WITH LATITUDE AND ALTITUDE OF POINTS OF INTEREST IN CALIFORNIA.

Location.	Lat.	Alt.	Aver. Max.	Aver. Min.	Mean.
Anaheim	33.51	133	92.	50.	67.
Auburn	38.57	1,360	83.	39.	58.
Caliente	35.17	1,290	83.	45.	64.
Calistoga	38.38	363	86.	36.	59.
Chico	39.44	193	88.42	46.08	65.
Coltoa	34.02	965	89.42	41.66	62.08
Colfax	39.08	2,422	85.42	41.50	56.91
Dixon	36.00	25	81.	44.92	60.
Fresno	36.45	292	90.12	45.	64.34
Galt	38.18	50	88.	43.	62.
Geysers	38.49	......	......	......	......
Gilroy	36.59	193	87.	38.	58.
Indio	33.46	20	100.	50.	73.
Keene	35.12	2,705	81.	32.	54.
Livermore	37.42	485	88.	39.	58.
Los Angeles	34.03	293	89.67	51.	64.75
Martinez	38.02	10	76.	42.	56.
Marysville	39.10	66	88.17	42.75	63.58
Merced	37.20	171	89.	41.	63.
Mojave	35.02	2,751	87.	47.	63.
Monterey	36.37	5	78.50	42.83	57.40
Napa	38.21	20	87.58	37.50	59.19
Oakland	37.49	12	69.33	42.58	54.75
Paso Robles	35.38	......	......	......	56.
Redding	40.37	557	86.33	43.16	61.58
Red Bluff	39.08	308	90.50	45.67	64.
Reno	39.31	4,497	72.	32.	49.
Salinas	36.41	44	75.	42	56.
Sacramento	38.36	30	80.58	44.92	60.33
San Diego	32.45	......	82.83	47.50	61.
Santa Barbara	34.26	30	81.	46.18	60.
San Mateo	37.34	22	78.	44.	54.
San Luis Obispo	35.18	......	......	......	56.96
San Francisco	37.48	......	76.25	42.33	55.25
San Jose	37.21	91	83.08	39.83	56.75
Santa Cruz	36.58	18	82.67	42.42	58.08
Santa Rosa	37.00	20	85.	30.	57.
Stockton	37.58	23	79.50	41.50	58.
Sumner	35.24	415	89.	43.	64.
Summit	39.20	7,017	58.17	21.	40.66
Tehachapi	35.06	3,964	78.	32.	52.
Truckee	39.20	5,819	68.83	21.25	43.
Tulare	36.13	282	87.	43.	64.
Woodland	38.41	63	86.	49.	61
Yosemite Valley	37.47	......	......	......	......
Yuma	32.44	140	93.	58.	74.

 

EXPOSURE.

The situation suitable for the olive in one locality, will not always answer in another. A southerly exposure, where there is a good, free circulation of air, is generally the most desirable, especially as one goes northward. In any latitude, a southern exposure, is best calculated to receive the sunshine from early sunrise to sunset. It receives all there is to give. A northerly exposure receives the sun's rays obliquely, and then only after it has risen high in the heavens; and so, as the sum total of heat is less, the fruit ripens late, and in some cases not at all. An easterly exposure has the full force of the sun all the morning, but after noon, there is either no sunshine, or feeble, slanting rays, so that at the very time when the sunlight is strongest, an easterly position is deprived of its warmth altogether. Of course a westerly exposure is just the reverse of this, and after a morning passed in the shade, the tree is suddenly overwhelmed with sunlight at a time of day when the temperature is the highest. In summer, the variations of temperature in half an hour's time, may be from sixty to ninety-eight degrees. This sudden change is as harmful to plants as to animals. The more perpendicular the sun's rays are, naturally, the more heat they give; so also the farther north one goes, the more oblique they become and lessen in warmth. Therefore the higher the latitude, the greater the necessity of a hillside to receive the sun perpendicularly. A well-protected situation, with a southern exposure, may be considered equal to a point one degree farther south. The influence of a protection, be it a mountain range, a fence, or a hedge, is felt for a distance equal to eleven times its height, but at the point where the protecting influence is lost, the wind has greater power than if the shelter did not exist. Strong and impetuous winds injure the olive, especially sea winds, on account of their vapor and saline properties.

 

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1. "Nor burning heat nor icy cold endures the olive."
2. January, 1888.