The Olive Its Culture in Theory and Practice/Chapter 9
Pruning
CHAPTER IX.
"Quien quiere aceite, labra; quien quiere mas, estercola; y quien quiere mucho mas, corta y poda a su tiempo."
Vicente Payo.[1]
The olive should be pruned every two years, but the process will have to be varied with the species cultivated. Some varieties need the knife, others require it but little. Still it is necessary to prune the olive, but skill, knowledge, and attention to the wants of the tree, are needful to secure the best results.
Some of the old world saws embody this truth and in few words gives us the experience of centuries.
"He who plows, hopes; he who manures, begs; but he who prunes the olive, obliges it to produce."
"For the olive and the oak, the spade below, and the hatchet above."
"Strip me and I will dress you, make me poor and I will make you rich."
No one would think of adopting these maxims literally in their treatment of the tree but their tendency is evident.
TO SHAPE THE YOUNG TREE.
When the young tree has attained a height of from four to five feet, and has a sufficient number of lateral branches, presenting the appearance of Fig. 5, cut off the top at A in the early spring, leaving the three topmost branches on each side, and shorten the lower ones. Each branch is developed during the year as shown in Fig. 6, and is then cut again at A, and
Fig. 5. 
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Fig. 6. 
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Fig. 7.
Fig. 8
exposes much surface to the sun, which is the object desired. The olive produces fruit on two years wood only. This point the pruner should always bear in mind, and direct his efforts to multiply these shoots in order to increase production.
The aim should be to distribute the sap equally throughout; keep the extension of branches within proper limits, and give air to the interior. Take out the dead wood and fruitless branches, called "gluttons" because they take to themselves the best forces of the tree. Cut out those parts that are not sound or are subject to canker. Do not allow the branches to cross each other; favor new shoots by lateral pruning when there are vacant places to fill. In Provence, contrary to the custom elsewhere, they prune their trees each year, keeping them near the ground. This practice besides rendering the fruit more abundant and fine, permits a more careful gathering by hand. The trees thus treated will not last so long it is true, but this inconvenience is largely compensated by the other advantages attending this mode of pruning.
The olive has precisely the same mode of vegetation as the peach, with this difference only, that new shoots are easily formed from old wood. The branches and roots of a tree are proportional, contributing mutually to the growth of each other, and therefore the one suffers if the other is cut. If the strong branches of a vigorous tree are pruned very long, the roots are strengthened, the said branches increased in size, the tree runs to wood and does not fructify. If on the contrary they are pruned very short, and the lesser branches taken off also, the tree is weakened and the roots with it. It is necessary to take off the lesser branches of a vigorous olive tree, and also the strong branches to a reasonable length, always with the idea of preserving the proportion between the roots and branches.
The tree is nourished by its sap; this commences to move with the increase of temperature in Spring, generally in March. Drawn from the soil by the roots, it circulates throughout the tree with increasing freedom as it approaches the extremities, where the tender twigs present less opposition to its course than the older wood. Having reached the leaves, the lungs of the tree, it undergoes some change in its properties and then returns to the roots again; so we have the ascending sap and the descending sap.
The descent of the sap can be verified and turned to advantage. It is claimed that the tree can be compelled to bear fruit whether it will or no. Having selected a fruit branch, ring the bark near its base, making a perfect ring whose ends meet, A double-bladed knife with the blades about half an inch apart is the proper instrument to use. The descending sap will be forced into fruit and the yield of that particular branch will be in marked contrast to its neighbors. The upper side of the ring will exude sap and it will finally swell into a circle there showing its desire to come down. It is claimed that this ringing of the bark of minor branches can be done annually without any detriment to the tree. It will be better to select horizontal branches, as without the bark and with a weight of fruit, vertical branches are apt to be broken off by the wind. But as much is required from a tree by this process, so, more than usual care must be expended on it in cultivation and manuring. The tendency of a tree is to reach the height of its species, and as only the vertical branches are useful for this purpose, the sap always tends to nourish the upright branches at the expense of the horizontal and lower ones.
It is necessary to avoid pruning too long, which would carry the sap to the extremities of the branches to the detriment and destruction of the center. On the other hand too short pruning would force the sap into a small number of buds that would be found on the young branches and flowing back to the old, would result in false wood, that is, branches out of place and contrary to nature. If one side of a tree grows with too much vigor the strong branches should be pruned short but the feeble ones left long in order to encourage the sap to flow into them, and on the other hand the reverse should be done with the feeble side, the weaker branches should be cut off, leaving only enough for appearance sake, and the stronger ones pruned long.
The action of the sap on the buds of a vertical branch is in proportion to their distance from the base of that branch. So the new shoots produced by the buds of a pruned branch will be stronger the nearer they are to its base. But if a branch is bent over, or arched, the bud in the highest position will produce the strongest germ, and the rest will be weaker the nearer they approach the extremity. In horizontal branches the case is different. The buds on the upper side are generally stronger than those nearest the ground. So, if the last bud on a branch is on the lower side, and the next to the last on the upper, the latter will be the stronger.
All branches that grow strong where they should be weak, and vice versa, are contrary to nature and should be cut off. The leaves have a powerful influence over the quantity and movement of the sap. This is augmented or diminished in proportion to their number. If an olive is robbed of its leaves, the flow of the sap is checked and the fruit falls. So where a tree has an excess of vigor, it may be contained within more reasonable bounds by thinning out the leaves.
The wild olive tree, or the tree from seed, if never transplanted, its tap root unclipped, is perfectly proportioned, its stem is straight, its bark smooth, its branches arch in beautiful equality, making a perfectly formed crown. But in the cultivated tree, the tree from a cutting, the tree that has already felt the knife, the order of nature has been disarranged and the tree, far from making a regular growth, if left to itself, will often take a most uncouth and ill-proportioned shape, and in appearance alone calls for the pruning knife.
The first six branches left on a young tree, three on each side, become the principal or primary branches of the tree, from these grow others called the secondary which in turn produce those of the third order. From these spring a multitude of small branches and twigs of one, two and three years of age. Those of two and three years are the fruit branches, those of one year will bear the following season.
The lower and horizontal branches produce the fruit in an olive. So a very general rule for pruning would be to preserve all lateral branches possible, with a due regard to the proportion of the crown, and to cut away those that are perpendicular to the trunk. The branches called "gluttons" are peculiar to the cultivated tree and need to be cut away, as they merely rob the plant of just so much vitality, without any compensation whatever. The glutton is a degenerated fruit branch, or one that appears where a fruit branch should be. They may be recognized by the speed with which they grow, by the broadness of their base, and by the appearance of the bark which, though green, is not smooth and shining, but rough and seamed. In shape also they are not rounded, but flattened on one side or the other. The color of the bark on the lower side is likewise of a dark brown. These distinctive characteristics are consequent to the over abundant flow of the sap, which the glutton draws to itself.
Though every two years is generally considered often enough to thoroughly prune an olive, there is abundant work for the knife each year after the crop is gathered, in taking off the dead, weak, and sickly branches, to the end that the sap may go to fruit, and not be obliged to keep useless wood in life. The tree so treated will be better able to resist frost, will bloom and yield more heavily, and its olives will contain more oil than do those of one that does not receive this care.
The olive is exceedingly subject to a species of dry rot, and unskillful pruning may actually cause it.
Branches should be cut perpendicularly to the trunk, and from the lower side to the upper, as otherwise, in falling, a strip of bark is apt to be carried away and a grievous wound caused to the tree. The cut should never force the bark out but always press it in.
It is better to avoid taking off large limbs, as the surface exposed by the stump of the branch is a source of danger to the tree. The larger this surface, the more difficult for the bark to close over it, and like injuries to the human body, unless the wound is thoroughly healed, it may cause the death of the patient. For this reason, if the cut is made perpendicularly to the tree, it presents less surface for the sun and rain to corrode, and for the fatal rot to take hold of, and finally eat out the heart of the tree. The cut should be made as cleanly as possible, and some of the wood scooped out in order to help nature cover it again with the bark. The whole should be covered with grafting wax or a mixture of cow-dung and clay.
If the olive is pruned while the sap is rising, or still worse while in flower, each branch lopped off is a mortal stab, a wound through which the tree will loose its life blood. The sap will run heavily for some days, especially if they are damp and rainy, no time being afforded nature to close the outlets made with the pruning knife.
The tree will have lost, to no purpose, that which might have nourished it, its vigor will be observed to diminish from that time forth, and little by little it will dry up and die.
Thus the very great importance of early pruning is inculcated, in order to give time for the closing of the cicatrices before the rising of the sap in March.
Experience shows that an olive, although it may not have been pruned in many years, and has not strength to put out new shoots, will flower and fructify every year. But in the majority of instances the flower does not set, or if the fruit forms it soon falls off. All this because the sap canals in the branches are obstructed, if not obliterated, and the tree cannot receive sufficient nourishment to maintain its produce.
On the other hand, if a tree is observed to make wood heavily, and to grow barren and give no berries, it is a sign that it has been over pruned. Such cases are rare, but when they occur the remedy is to make the tree fast for a while, neither cultivate, nor fertilize nor prune it, for several years, when the good effect of this treatment will be apparent.
The top of an olive, the parts to which the sap flows with most abundance and activity, should be considered as a vigorous tree, while the lower part which receives less, as a weak tree. So the pruner should take off the strong upper branches and leave the lesser ones, and reverse the process with the lower part, lopping off the puny branches and leaving the more vigorous.
To prune in winter at a period of frost is dangerous. The limbs are exceedingly brittle at this time, and break off at the slighest provocation.
When the tree is provided with sufficient branches to clothe it, the real work of the pruner begins, which is to oblige it to bear fruit. To open a tree to sun and air is not to strip it of all shade. Its leaves are necessary to prevent the scorching of tender bark and young leaves by the sun. The variety should indicate the treatment. The Spanish Manzanillo, which has been planted to some extent in California is sparse of leaf and requires the knife only to a limited degree, and then principally in cleaning rather than pruning. All pruning that is ill timed or out of season does harm, and may be an actual drawback by obstructing and impeding the natural flow of sap. Still the olive with the tremendous strides that its vegetation makes, really demands the knife. If left to itself its center becomes a mat of cris cross branches, its growth ceases, and it falls a prey to a variety of diseases. There are two classes of branches that the olive should be deprived of:
First, the irregular, the unfruitful, the diseased, the dead or dying.
Second, all useless branches, over and above what the tree is able to carry, even though they should be the fruit branches of the following year, and all the "gluttons."
An olive tree that is heavily loaded down with branches or with fruit, is in a far from healthy state and by its appearance alone accuses the ignorance of its owner. If it has more branches than its strength is able to nourish, it becomes weakened, if more fruit, the latter appear poor, weazened, and half ripe. The last is damaging to the crop, but the first ruins the tree.
THE TIME TO PRUNE.
This must vary with the climate, soil and variety to be dealt with. It seems quite clear that no pruning can be done to advantage with the crop still on the trees, so it must be put off till the berries are gathered. This would give a period from October to March in which to carry on this necesssry labor.
The year in which an olive orchard is thoroughly pruned is one of a light crop, the real benefit received from this process, not being manifested until the following year. So in an orchard of any extent it would be better to divide it into halves or even thirds and to prune one of these parts each year.
It is greatly to be desired that the clippings should not be allowed to lie about under the trees but should be immediately burnt on the spot. The tendency with us will probably be to save as much available wood as possible for future cuttings; in that case such wood as is selected for this purpose should be disinfected and the remainder burned. In this way a multitude of noxious insects, adhering to the bark and leaves, are destroyed at once; and if not so treated, live to propagate, and renew their attacks on the trees in increased numbers.
Pruning, as we have seen, consists in keeping the trees well shaped and in good disposition for bearing the most fruit. But it sometimes happens that more heroic remedies are demanded.
When an olive orchard appears to be healthy in every respect but gives no fruit, it is owing to one of three causes. First; That the trees are too near together. Second; That the sap has been corrupted and makes only wood, and Third, that there are trees or plants in the vicinity that do them harm.
When the trees are too near together, the ground is unable to sustain so many and it is necessary to transplant a portion of them. When this necessity is apparent every third, or every other tree will have to come out. This is likely to be the experience of many olive growers in this State. Fortunately the tree will bear it.
The first step is to cut the tree down to the crotch leaving four arms or stumps, the nucleus of the future primary branches of the new tree. It is then dug up with as much earth as possible and transported to the hole already prepared for it. In the spring of 1883, fifteen hundred olive trees between ten and twenty years of age were thus transplanted on the Quito Farm, with a loss of only six trees. When the sap has become corrupted it is necessary to take off one of the primary or mother branches in order to check the tendency to make only wood. When the trees have been damaged by the proximity of others prejudicial to them, such as the pine or the cork oak (the latter breeds a worm, about its roots which is fatal to the olive) the weakly parts will have to be severely pruned. When they are attacked by an infinity of little shell like warts which spread up from the trunk to the lower branches, there is no remedy but to cut the tree down to the crotch and allow it to begin over again. But it must not be forgotten that this treatment is an extreme measure, and only to be availed of when all others have failed.
The primary, or mother branches of an olive, are its arms, and are not to be lopped off without a good and sufficient reason. Although the tree may grow and flourish for many years, its new branches never will have the strength and exuberence of their predecessors.
That one of these branches appears to be ailing, is not cause enough to cut it off. Manuring and cultivating about the tree may give it all that it needs. Watch it till spring, and then if it fails to flower, it had better be condemned.
Thus we have seen that in pruning there are three different degrees, the cleaning, or light pruning; the pruning itself, and the more severe measure of cutting back. It is necessary to clean up the trees with the knife after the crop is in, every year, say in January or February, and if the operation is carried a little further, and the tree is really pruned every year, it will be found advantageous.
If the regular pruning is deferred to periods of two or three years, the wounds given the tree have to be so much the larger, and are so much the more difficult to recover from, or detract so much from the force of the tree. Then also, the season after a full pruning is one of a very light crop, making a very heavy crop the second year. This results in making either a very expensive crop to gather, that is if it is done carefully, or if not, by being done hurriedly, the branches are broken and damaged, and the prospect of the next years fruitage is destroyed.
The olive is sometimes called a biennial, but a moments reflection must convince anyone familiar with the tree, that it is an annual. Does it not make a yearly effort to flower and fruit? Then encourage it and the result will be an annual crop. Annual pruning will give a moderate crop every year, will distribute the labor of pruning and harvesting more evenly, and will be most advantageous to the trees.
Light pruning necessitates heavy manuring in order to successfully carry the excess of wood and branches. Real scientific pruning can be safely said to be almost unknown. There are more humbugs in this branch of horticulture, than in any other. Because a certain line of treatment may be desirable in a given locality, it does not follow that it is so in another. Certainly a very undesirable arrangement would be that the pruner should have the wood, as he then sets to work and makes all he can, utterly regardless of the result to the trees.
Successful pruning is founded upon the following propositions:
First: That the olive fruits on two years old wood only.
Second: That the flowers do not develop except when exposed to the sun for a number of hours of the day.
Third: That the horizontal are the fruitful branches, and the vertical branches are sterile.
Fourth: That too many branches in fruit results in a poor crop and over taxes the tree.
Fifth: That the pruning should vary according to the variety.
Sixth: That the soil, exposure, and altitude, all affect the growth and fructification in a different manner. The richer soil can support
FIG. 9.
THE PINE OR CONE SHAPE.
more vegetation, and hence, in such soil, the tree will require only light pruning, while on a poorer soil, full pruning is necessary including even the horizontals, which have borne fruit some years back.
Trees with a southern and eastern exposure can be allowed to grow higher, than those with a northern and western exposure, as the outlook is warmer.
Trees on the plain can be permitted to grow taller than those on the hills, in order to throw them open to all the air and sun possible. On the other hand, those on the hills are kept lower, so that they may receive the reflected heat and escape the wind and its drying effect.
The olive if kept low will have more vigor than if allowed to grow high, but do not oppose the nature of the tree too much. If it is of a variety that attains a great stature, to a certain extent it must be allowed to have its own way.
FIG. 10.
THE BASKET OR GOBLET SHAPE.
The pendant branches which guard it from the heat of the sun, should be preserved as much as possible. When a tree has produced heavily, the horizontal, or fruitful limbs, should be pruned to a certain extent.
A good rule for a well-pruned tree is, that one should be able to put the hand into the interior of the tree without holding off the other branches.
The olive is given four different shapes:
The natural, or uncorrected form.
The Pine or Cone shape.
The Basket or Goblet shape.
The Umbrella shape.
The objections to allowing it to grow at will are, that it grows too high, its upper branches are mere "gluttons," or suckers of sap, which rob the lower, or fruitful part of the tree, of what might result in well developed fruit: that the sun and light are kept out, the principal agents of fructification, resulting in the fruit being found only on the outside of the tree, where the sun and light have access to it. Neglected in this way, the tree finally, tired of its efforts, refuses to give a crop oftener than every alternate year.
The Pine or Cone shape is better, but the best form, and almost the only possible one for large trees, is the Basket or Goblet shape. This exposes the largest surface to sun and air. The Umbrella shape is the worst of all, as it can only be achieved by directly opposing the habits of the tree. The round well-opened crown will be the most natural way to shape trees of small size.
The character of the soil must be taken into account in fixing the height and forming the crown of a young tree. In a poor and arid soil, it will be best not to make the trunk higher than from three to four feet, as in such a soil, the limited nutritous qualities will, with difficulty reach its branches, if placed too high. On the other hand, if the soil is rich, the crown may be placed from five to six feet from the ground.
- ↑ He who wishes oil, cultivates; he who wishes much oil manures; He who wishes an abundance of oil prunes at the right time.