By extracting EO from kumquats from very young trees , we have observed that the yield is nearly 10 times lower than that of older trees (20 years old). The perfume is also much more complex and long in the oil extracted from fruit from the older trees.
All trees were grafted on poncirus rootstock which gives good quality fruit, the influence of the rootstock on fruit quality has been extensively. It should be noted that paroductive and rapidly growing rootstocks (especially Macraphyla) degrade the quality of the fruit.
We know that the quality of the fruit varies with the age of the tree, in citrus the age of the tree is even the most important factor. Older trees (18 years and more in the publication) give a fruit with a rich pericarp (high TSS), trees that are less than 3 years old give poor quality fruit.
Grapefruit trees it take a minimum age of 7 years to produce good fruit.
The second quality factor is the position of the fruit on the tree, the fruit at the top of the tree canopy, and those with a southern exposure are better.
In our two sources used for EO extraction, we can rule out the 3rd quality factor which is deficient or excessive irrigation or fertilization. As both young and old trees received controlled fertilization rich in micronutrients, without excess.
On the other hand, we know the importance of the nutrient and metal content of fertilization, (https://www.scirp.org/html/76086_76086.htm) content which has a high cost hence a limited use in the cultivation of decorative citrus sold young.
And finally the 4th factor which is the climate does not play a part here because all of the fruit is from the same climate.
The importance of the age of the trees , means time, years and even by bringing together all the quality factors you can only obtain a good quality EO from mature trees - well irrigated, well nourished and well pruned.