Grafting Fruit Trees: cleft grafting, shield budding, and top working
The grafting and joining of one plant part to another part of the same plant or a separate plant has been practiced by humans for thousands of years. This work can be very fun and rewarding and offers a glimpse into the magical world of plants.
Last winter we got a call from a man in North East Portland who had an old pear tree in his back yard that was falling over. The pear tree had been propagated by his ancestors in Macedonia his father had brought back cuttings 50 years ago, Marbott's nursery had grafted them onto roostocks at that time, and he had planted one of the resulting trees. Last year the tree begann to fall over and he was worried that he was going to loose this part of his heritage. With our help, we were able to take cuttings from his heirloom pear and create 5 new trees so that he could replant them and pass one on to his son.
Last Fall we got a call from Logsdon Farm House Ales. They had Chaerbeekse Kriek sour cherry trees that they had purchased in Sint Truiden, Belgium. They needed more trees in order to make their farm house cherry ale in larger batches. So in August we went out to Hood River to take cuttings and bud graft 40 more trees for the brewery.
This winter we will be top working several old large apple trees in Portland to new varieties. This is an excellent option for backyard fruit growers. Often we get contacted by homeowners who have a large tree, and they just don't like the fruit. Or they simply don't want 500 lbs of the same fruit. So instead of having one large tree that puts on 500 lbs of Honey Crisp apples, for example, we can top work individual branches to different varieties. So what was once a large tree with only Honey Crisp apples, is now a large tree with not only Honey Crisp, but also Spartan, Chehalis, Empire, Ashmead's Kernel, Hudson's Golden Gem, Akane, Fuji, Braeburn, Granny Smith, Macoun, MacIntosh, ect. So instead of one large harvest one time of year, some of our clients now have a 4 month harvest window of over 20 different varieties of apple all from one tree!
Most of the fruit trees we graft respond best when the bark is 'slipping' and the vegetative buds start to push in late March and early April or when we start to see 60 degree days and no freezing nights.
Fruit tree varieties are propagated asexually. Meaning not from seed, but by cutting. In order to get a Spartan apple you need wood from a Spartan apple tree, not the seed from a Spartan apple tree. On a fruit tree this fruit wood or cutting is called a scion. A scion is a cutting of 1 year old wood that is roughly the thickness of a pencil.
Once you have the scion you can either use it to graft onto a new young rootstock, or onto an existing tree's framework. The most common grafts we do are cleft grafting (in winter/spring), chip budding in fall for stone fruits, and top working in late spring.
When the bark is 'slipping', sap is flowing in the tree and it is more possible to ensure good contact between the cambium of the rootstock and the scion. In order for a graft to successfully take, the contact between the two plants' cambia or other meristematic tissue must be sufficient, and the two species should be in the same botanical family. The closer the relationship, the better.
The main grafting styles we use are rind grafting, cleft grafting, and shield budding.
Rind grafting is employed when we top-work an existing tree- removing some amount of the existing branches and attaching 1 year old scion wood to the cambium layer between the bark and the sapwood of the tree. This style of grafting is a great way to restore or re-establish the fruiting potential of an existing tree. The grafted branches have a much larger, more established root system to draw nutrients and water from and can grow much faster than a newly planted tree. Last season, a client had a semi-dwarf golden delicious apple tree and wasn't satisfied with the flavor of the fruit. We grafted two dozen different apple varieties onto the existing tree so they could have a more diverse apple crop and be assured of proper pollination. Another client had a diseased pink-lady which we re-grafted to Spartan scion which is more disease resistant and regionally adapted. These clients will get to enjoy healthy fruit yields sooner than if they had replanted a young tree, however it's still a loss of two years of production as new fruit wood develops on the young grafts.
Cleft grafting is a technique we use to join 1 year old scion wood to 1 year-old rootstock when raising young trees. Because we perform this graft on two pieces of wood above ground, this is called bench grafting and can be done at a workbench or table, as opposed to the other styles which we perform in the field. This is a great way to combine the genetic advantages of a particular root system (fibrous, vigorous growth, tree size, disease resistance) with the genetic advantages of a the scion wood which will eventually produce the fruit. Bench grafting is an economical choice for larger-scale orchard production and for propagating new trees with wood from fruit trees you enjoy.
Shield budding, also known as chip budding or t-budding is a less intensive grafting technique we have used to introduce pollenizers in existing orchards and to attach heritage cherry varieties to young whips in the field.