Many a time, you’d have observed that many fruit trees planted by seed can take three to eight years to start producing fruits. That’s perhaps the long time. For this reason, there are various scientific innovations that have come into existence so that farmers could purchase immediately fruiting trees that are grafted on already established rootstock.
Commercial fruit trees usually consist of two parts vis-à-vis SCION (flowering or fruiting part) which makes up most of the tree above the ground and the ROOTSTOCK which consists of the roots and the lower portion of the trunk. Hence, rootstock is the base and root portion of a grafted plant. A scion is grafted onto rootstock in order to create a new plant with superior qualities.
The scion and rootstock must be of closely related species in order for the graft to be successful. For example, fruit trees like cherry and plum could be a rootstock and scion for each other but an apple fruit tree cannot be used as rootstock for cherry scion and vice versa. The selection of rootstock doesn’t only depend on their close relation to the desired plant but also on the traits that it would impart in the desired plant. There are more scion varieties available than rootstock varieties. So, grafters usually look for naturally growing trees, naturally occurring plant mutation or genetically bred plants to use as rootstock. Once a successful rootstock is identified, it then propagated asexually to create clones of it for use as future rootstock.
Rootstocks are mostly used to create very specific plant traits. Rootstocks determine the longevity of the plant, resistance to pests and diseases, cold hardiness, fruit yield, and the size of the tree, its root system and the tree’s ability to adapt to soil types. Also, fruit trees grown from rootstock tend to produce trees that immediately fruit, rather than the 3-8 years it takes to get fruit from a tree grown from seed. Larger fruit trees are grafted to dwarf fruit tree rootstock to create dwarf or semi-dwarf varieties which are easier to grow, and allow growers to grow more trees per acre with an immediate fruit harvest, hence, producing more fruit per acre.
Whilst most scientific attention has focused on developing rootstocks for apple trees, rootstocks are also important for growing other fruit trees like pears, plums, cherries etc. High land values and increases in all other farming costs make it imperative that apples be produced economically and an early return on the investment be realized. The use of appropriate apple rootstocks has greatly improved the economics of growing apples. Depending on which rootstock is used, apple trees may be broadly classified into 3 categories: STANDARD, DWARF AND SEMI DWARF.
That huge old apple tree in the traditional orchards you see is a standard. These trees can grow 25’ or more if left un-pruned. With good pruning, standard size trees can be planted at about 26 feet x 20 feet with 84 trees per acre; these trees will attain a height of about 24 feet. Standards live longer and bear more fruit than dwarf varieties. They are slow to start cropping taking around 5-8 years to come into bearing and costly to prune and pick. They can live 50 years or longer.
Dwarf trees are small trees for small spaces. They are easy to prune and harvest because they don’t grow as tall. These rootstocks are very precocious and high yielding. Most dwarfs begin bearing fruit in 3-5 years. Dwarfing rootstocks have a limited root volume and benefit from supplemental irrigation in dry seasons and in droughty soils. Dwarfing rootstocks also benefit from total tree support for the life of the orchard.
Semi-Dwarf trees are somewhere in between the other two. They can range from 10-16’ tall and need timely pruning to keep them in shape. They are considered very productive. Their fruits are the same size as standards. Fruit bearing generally begins in 3-5 years and can live up to 60 years.
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