Olive trees have been grafted since ancient times, though grafting isn’t currently believed to be the best method to spread olives. Most olive trees have been started from rooted cuttings. Hard-to-root varieties may be grafted onto seedlings or suckers transplanted from the foundation of adult trees. Even though researchers are working on developing advanced rootstocks and processes, grafted olives are usually considered to be weaker than rooted cutting and some rootstocks can spread disease.
Reasons for Grafting
Some trees have very desirable fruit characteristics and feeble roots. Other have strong roots but little or no fruit. Grafting can combine the powerful roots and good fruit into the exact same tree. Moreover, some rootstocks increase disease resistance or create the tree better able to live in another manner. In order to be prosperous, both varieties have to be harmonious, meaning that the cambium, or increase tissue under the bark, must fuse together.
Grafting Methods
Small trees are grafted by budding, where a little grass is eliminated from a desired olive tree and slid to the bark on a little seedling. A branch grows from the bud and the remaining branches are taken out of the seedling. In cleft grafting, which is also used with olives, the rootstock is cut and split, then a branch of the desirable tree inserted. Larger trees may also be top worked or bark grafted, which involves inserting little branches of the desirable variety in the border of a cut-off tree division.
Tree Strength
Grafted olives tend to be weaker than trees started from cuttings. This may be because of a weak graft marriage, where the cambium of the 2 varieties didn’t completely fuse together. Additionally, it may be because sap and nutrients cannot completely cross from one variety to another. Wild olives are often used as the rootstock. Because olives have been cultivated and selectively bred for at least 7,000 years, wild olives are farther removed from domestic varieties than most other fruit.
Disease Resistance Or Not
In the 1970s, the variety “Oblonga” was widely promoted as a solution to verticillium wilt in olives, since research showed that olives grown on “Oblonga” rootstock did not get the disease. Since that time, it has been found that “Oblonga” is immune to verticillum wilt, but might haven it without showing any signs. The fungus passes from the “Oblonga” rootstock into the top growth and the tree dies suddenly. Thus, one of the greatest rootstocks became one of the worst, demonstrating the demand for new rootstock development even after 7,000 years.