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Head transplant: the art of avocado grafting October 1st, 2017 by

Grafting is the surest way to get the fruit you want. If you grow a fruit from the seed, the new plant may not be the same as the one you planted.  Although grafting was practiced in ancient Greece and China, even American trees like avocados can be grafted, as my agronomist wife, Ana Gonzales, recently explained to me in Cochabamba, Bolivia.

Ana has been grafting avocados for a couple of years now, in part because she knew someone who planted a grove of the small, but tasty Hass variety. He went to the trouble of flying in grafted trees from Chile. When the owner sold his land for a new housing development, Ana wanted to keep the variety going before the trees were all destroyed. She found an agronomist who ran a nursery and was willing to show her how to do the grafts. The second year she practiced on her own, and although she lost many of her trees that year, practice pays off and she’s pretty good at grafting now.

The first step is to grow the rootstock. We save all of the avocado seeds or pits at our house. We soak the pits in shallow water for a few days, before planting them in soil in a black plastic bag. It may take a year to grow into a seedling big enough to graft.

When you cut a tree you open the door for pathogens, so Ana starts by washing her tools in soapy water and disinfecting them with a weak bleach solution. She cleans the tools after working on each tree to avoid spreading fungi and bacteria which might kill the little plant.

I am a bit surprised when Ana takes the pruning shears to a flourishing seedling and cuts off its entire, leafy top. Now it looks more like a pencil than a tree. She uses a razor to slice a vertical cut into the stump of the decapitated seedling. This is going to be the rootstock of a new tree.

Next, she takes the scions, the small branches she has cut from the tree she wants to reproduce. When Ana began, she would go to orchards in the Cochabamba Valley to look for Haas avocados. She got several scions from trees still left on that housing estate that had once been an avocado grove. But it is better if you have the donor tree closer to hand. Freshness really matters in grafting.

The rootstock and the scion should be about the same diameter. Any mismatch in size and the two pieces of living wood don’t meld. Ana cuts the tip of the scion into a long, thin wedge and gently, but firmly slips it into the razor cut of the rootstock.

Ana says that sun and wind can dry out the graft and kill it. So she wraps a strip of paraffin tape around the wound, to bind the scion to the rootstock. She tears off a bit of newspaper, soaks it in water and wraps it around the top of her grafted tree, and then covers the newspaper with a small, new plastic bag and ties off the bottom of the bag, to keep it moist.

Ana sells most of the successful grafts, usually to family and friends. She sold one to a cousin and every time we visit we step out into the garden to check on Ana’s avocado tree, which is doing well.

 

Ana offers a guarantee. If the customer plants a tree and it dies, she replaces it. Most orchard deaths are due to careless transplanting or neglect. You never know what people are going to do to your little tree, but Ana gives her customers the benefit of the doubt and a replacement. She doesn’t want any disappointed customers. Human relations are fragile, like a grafted tree; it’s important to nurture them both.

Further viewing

Watch a detailed training video on grafting mango trees

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