How Grafting is done
Graft plant has 2 parts. Lower portion is from the seedling and is called rootstock. Upper portion is from the mother plant and is called scion. Rootstock should be a sturdy disease free seedling with a strong tap root system. For mango grafts bigger mango stones of wild variety are sown in beds. These produce stout seedlings.
Scion should be a matured stem from fresh growth of the mother plant. It should have a dormant bulged vegetative epical bud. Scion should be free from diseases and insects like stem borer. It is better to cut off the leaves of the scion on the mother plant itself 4 days before separation. Do not pluck the leaves. But cut it off retaining the stock of the leaf on the stem itself. Use only the fresh scions for grafting. However, it can be stored in a wet gunny bag for 2 days.
The principle of grafting is same in all the methods. Two stems will join if the cambium cell layers of both stems are tied together after giving level cuts. In another method roots are induced on the stem to get independent plant. Many methods of grafting are in practice based on this basic principle.
Approach Grafting
This is an age old method of grafting. This is in practice in important crop plants like mango etc. Search a twig of the mother plant which matches with the stem of the seedling in size. In commercial nurseries, the nursery of dwarf mother plants are maintained for the purpose of approach grafting. Otherwise a platform is put to facilitate grafting. Bring both the stems together and put marks. Then give level cuts of 2 inches on both the stems. Let the cuts be of 30 to 40 percent of the thickness of the stems. Use sharp knife to give level cuts. Do not damage the stems with a blunt knife. This point applies to all methods of grafting. Then keep both the stems together and tie with plastic tape. This tape avoids the entry of air and water inside the graft joint and avoids drying. Tying jute thread is necessary in this approach graft since both the stems are thick and stout.
The beginning of the rainy season is the ideal time for approach grafting this is usually between April and July in Kenya. Graft takes 2 to 3 months for healing. During that period seedlings need watering. It is easy if the rain does that job. Give vertical cut on the scion below the graft joint after the union seems perfect. Give one deeper cut after one week. This brings down the dependence of the scion on the mother plant. Scion starts absorbing water and nutrients from the seedling through the graft joint. Then separate the graft from the mother plant. Cut off the seedling above the graft joint. Keep on removing the sprouts on the rootstock below the union.
We can get a bigger plant in approach grafting by selecting bigger shoot for grafting. But we can produce limited number of plants in this method. Due to the heavier upper portion sometimes the approach graft plant bends and breaks at the graft union. Watering the seedlings is a difficult task on a large scale if the rain stops. Because of all these reasons approach grafting is not being practiced by commercial nurseries.
What we are using here is a common plastic strip. It is not a gum tape. Soft stretchable plastic of medium thickness is folded and cut for 1 inch width. This plastic strip avoids air and water entering the graft joint. Remove the tape after the graft union heals completely and the plant starts growing. Otherwise it makes constriction and limits the growth. The plant may even die. This point applies to all the methods of grafting.
Stone grafting
The commercial nurseries producing grafts in large numbers follow stone grafting. Though this is a simple method, the success rate depends on the skill of the grafter. Stone grafting is commonly practiced in mango, cashew etc. Sow the stones in beds with loose soil. Seedlings will lose the tap root while pulling it out if the soil is hard. Uproot the copper colored (in case of mango) young seedlings with entire root and the stone attached. Cut of the stem leaving 2 to 3 inches above the stone. Make a slit of 1 inch with a sharp knife. Select a scion of 4 inches in length and of pencil thickness. Give slant cut on both sides of the scion. Keep the scion in the slit of the rootstock and tie with the plastic strip. Only the plastic is enough to hold the union since the rootstock is soft. Make the packing air tight. Plant this tiny graft plant in a poly bag filled with potting mixture. Put a polythene pouch on the scion and keep the graft in a poly house.
Stone graft kept in an open place will fail. But in a greenhouse house the success rate is 70 to 80% in mango. Scion fails to sprout if the rootstock with leaves turned in to green is used. Graft fails to sprout if the stone is detached while pulling it out from the bed or at the time of grafting. The reason is the stone is the source of food for the graft plant till the scion produces green leaves. Successful graft starts sprouting in 2 to 3 weeks. Then take out the polythene pouch on the scion. Cut off the plastic strip once the union is perfect and the graft grows fast. Keep on removing the sprouts below the graft joint.
Softwood grafting
Now let us study the most popular method of grafting called soft wood grafting. This is in practice in mango, jackfruit, cashew, tamarind and in many more plants. We will take mango to explain the method. Grow seedling in a polythene bag for one season. Even the older plant is useful. Grafting is on the green-soft portion of the plant. Hence it is called soft wood grafting. The grafting method is as usual. Cut off the rootstock above the green portion of the stem. Keep few leaves below. Make a slit of 1 to 2-inch length. Give slant cut on both sides of the scion. Then keep the scion in the slit of the rootstock and tie with the plastic strip. Plastic is enough to keep the joint intact since the stem is soft. Ensure that the packing is made airtight.
Other grafting methods include:
- Rejuvenation of old tree –
- Bark grafting
- Side grafting
- Air Layering
- Budding or Bud grafting
