Olea europea sativa or Olea europea oleaster are outdoor trees. The name olea derives from the Greek word Elaila. Olive has been here in Europe from the tertiary period and the Phoenicians were the first farmers of this tree.
In the Bible, Noah, after the Deluge, saw a dove with an olive branch in its mouth like the symbol of peace between God and men. Olive is present in many books of Hebrew, Phoenician, Egyptian, Greek, and Roman authors. Pliny the elder in his Natural history (Naturalis historia-37 volumes-died in 79 A.D. because he approached too closely to the Vesuvius eruption at Pompeii) distinguished 15 varieties of olive. In the parable, Judges book (9: 8-9) one reads: As the trees set out to consecrate one tree as their king, they said to the Olive, “Reign thou over us” and the Olive answered, “Should I leave my [oil], wherewith by me they honour God and man, and go to be promoted over the trees?”
Olive is endemic to the Mediterranean, from the center of Italy and south, but also in the great lakes of the pre alps. Acid and alkaline soils are not a problem for it. It can tolerate hot, dry weather and also hot and cold winds. It grows slowly, but strong; and can achieve great age, as it can resprout from its trunk, even if you cut or burn it. Olea europea can live in favorable conditions even to 1500 m. (4,926 feet about). There are some specimen in the Algerian Sahara, and in the Hoggar mountain area, Olea Laperrini occurs at 2500 m. (8,107 feet) as a magnificent example of adaptation to foreign a environment.
For bonsai, the weak point of olive is cold tolerance, because it produces many fine roots that do not withstand protracted frosts. Leaves bear temperatures between 6 or 8C (43 or 46F), in colder zones it is better to cover soil with mulch or put it in an unheated garage. For soil, use 1 part Akadama, 1 part sand, 1 part peat. Also acceptable is 1 part sand, 1 part leave mold, 1 part peat. It is also desireable to add some form of limestone (Dolomite for example). The soil must be porous and be able to retain moisture.
There are three growth stages in the life of olive: childhood, youth and maturity. In childhood, olive grows only by a taproot, dedicating most of its vigor to form a trunk. Where there are cotyledons, this stage lasts 7 years and some callusing on the trunk can develop.
In youth, olive sprouts a second generation of roots that increase in proportion to the number of trunks. The crown is often unpleasantly enlarged with one or many great roots, while fine roots are deeper.This stage can occur in only one year with an air-layer of the trunk.
In maturity, olive stops to sprout deep roots and also grows out many fine superficial roots. The trunk loses its cylindrical shape, while bark becomes smooth to rugose and cracked. From this point it can live 800 to 1,000 years with a stately appearance.
Propagation from seeds is very difficult, with a 30% germination rate at the end of winter. It can be grown from cuttings with a diameter of 3cm (about 1 inch). The best time is the third waning moon, i.e. when olive gets ready to reawaken from winter. If the cutting is from 3 cm to 7 cm (2 to 3 inches) in diameter, a better time is two waning moons of fall with branches without leaves and with at least 5 nodes.
Pruning and Shaping
Olive has a bad reputation with regard to pruning. When a substantial stem is cut back the new growth is coarse and vigorous at the cut. The best time for pruning to shape is the fall, when there is waning moon, especially if the branches have a diameter larger than 3cm(1 inch). If one prunes in the spring or summer, there is a risk of inverse taper in this area due to the resultant coarse, congested growth. Eliminate buds in this part to minimize this effect. The second pruning to shape is accomplished after the spring and fall growth before a new vegetative cycle begins. Eliminate buds that grow up or down, in order to have alternate ramification to right and left of the principal branches.
Pinching differs according bud colors and age of the tree and the cycle of growth. The new buds and stems are usually green, violet or tan. In young trees, one cuts to the first or third set of leaves, according to the direction of the buds. When stems turn from violet to tan it will grow only a few more buds. With young and old trees, you pinch when the branch is still green or is almost violet, eliminating last couple of leaves. Also pinch out leaves and buds that grow downward . Stop pinching if the temperature is down to 10C (50F) or up 40C (104F). By pinching in this fashion you will have smaller leaves and shorter internodes. Generally, almost all the leaves that are on green stems ramify less than half as much as those on the violet stems.
Wire young trees and stems that are only 2-3 years old. Wire carefully from late fall to spring, and only as necessary to control the branches, olive wood is soft and easily damaged. In aged trees, wire is applied to older branches, but it is good idea to use raffia during dormancy.
Repot in the spring when buds sprout, removing 1/3 of the roots and eliminating old leaves by 1/3 every 2-3 years.
Water thoroughly, but to let it go dry after each watering, but not too much. My olive is watered a lot, but in each case, this depends on light, wind, humidity, and exposure. Olive prefers to be in full sun.
Feed with organic food with slow transfer, but use a normal feeding like others trees. It is also important to add trace elements at least once a year. This can be done with the use of a complete fertilizer with trace elements, or trace elements by themselves in time release form.
All styles, except formal upright and exposed roots, may be used. But employ no jin or shari because the wood cracks and decays quickly.
Pests and diseases include green aphids (especially if you have ants), red spiders mites, anthracnose, and Pseudomonas savastanoi.