In nature plant species have various mechanisms for reproduction. Seeds, rooting on the stem, tubers and suckers are the important ones. Plant propagation techniques became popular with modern horticulture for asexual multiplication of commercial plants in large numbers. Grafting is an age old practice. But its commercial application and new techniques started few decades ago. Tissue Culture is another popular asexual method of multiplication of plants. But it is commercially successful only in soft wood plants like banana, cardamom, flower and ornamental plant species.
Majority of the plants produce seeds. Then why do you need grafting? To answer this question let us understand the problems of seedlings first. The male part of the plant pollen unites with the female part ovule to form seed. Due to recombination of genes the next generation plant differs in its characters than its mother plant. This variation is more evident in case of cross pollination. Hence the seedlings from a sweet mango tree may give sour fruit. Best jackfruit may become useless in next generation. Off course this is the reason for the varietal diversity in nature. But in commercial horticulture we need plants with similar characters for good quality and yield. Here the grafting techniques help us a lot.
Seedlings take long time to bear fruit. But the grafted plants can give fruit after 2-3 years. Grafting technique is used to escape from certain diseases in some crops. Many ornamental plants do not produce seeds. At the same time, they do not root easily by stem cuttings. For the multiplication of such plants grafting technique is inevitable. Grafting is helpful to produce composite plants with many varieties and for the rejuvenation of old trees.
What is Grafting?
Grafting means uniting two plants of the same species. Shoot of a required variety plant is grafted on a seedling with a stout root system. Normally two different species will not unite. Grafting is restricted only to di-cot plants. It is not possible in mono-cot plants like coconut etc. Graft plant is dwarf by nature since it is from a lateral shoot. It spreads wider than its height. This helps for pruning, spraying, harvesting and for other cultural operations.
There are few problems too with grafted plants. Some grafts fail to grow into a tree affecting the yield. In most of the species the graft plant will not grow in to a huge tree. Hence they are not useful for timber purpose.
Sometimes approach graft plants get damaged by heavy wind. Air layered plants without tap root system cannot tolerate drought. Depending on the root stock you may find slight variation in the quality of the fruit of the grafted plant. Due to incompatibility between root stock and scion the graft may fail to grow properly even after the success of grafting. Few viral and bacterial diseases are transmitted through graft plants in lime and pomegranate. Even then the grafted plants play a vital role in commercial horticulture.
High temperature and high humidity are necessary for the success of grafting. Hence heavy rainy seasons are not ideal for grafting. Natural warm climate is the best for the purpose. Hence most of the commercial nurseries erect greenhouses for grafting. But in medium rainfall areas a shade net house is enough for this purpose since the temperature and humidity remains ideal in the rainy season.