How grafting helps us enjoy more fruit trees and protect heritage trees!

The world of plant propagation is wondrous, with several different methods to grow new plants. People tend to be most familiar with plant reproduction through pollen fertilization, which produces viable seeds that can then germinate into a seedling under proper conditions.  Seed dispersal in itself is a curious thing, with plant adaptations for dispersal including avenues like wind (ie. dandelion puffs that float on a breeze), water (ie. mangrove pods that float), fire (ie. pine cones that open with a certain degree of heat), explosion (ie. pea pods that pop open after they dry out), and animal transport (ie. seeds that hook onto fur, or fruits that are eaten).

 

However, plants can also reproduce through a medley of asexual methods, using vegetative parts of the plant (think leaves, stem, or bud) to make a genetically identical ‘clone’ of the parent plant.  Examples of this include cuttings, layering, division, grafting, and tissue culture in a lab setting. The benefit of propagating plants using these strategies is that often the ‘child’ plants are already a good size when separated from the parent plant and, in the case of fruit-bearing plants, can produce fruit several years earlier than a plant borne by seed. 

City Fruit's Fruit Tree Specialist, Julian Garcia, finishes making a whip cut for a bench grafted apple.
Top grafting on a cherry tree!

Another reason why someone might choose to do vegetative propagation is to produce more plants with the same desired trait(s) as the parent plant. For example, say you’ve been enjoying the fruit off of a particular apple tree for years, but you are now moving to a different neighborhood and want to plant that same apple at your new home.  The tricky thing is that harvesting an apple from that tree and planting one of the seeds would grow a tree that produces apples different from its parent.  The reason for this is that each seed in an apple developed from an individual ovule that was fertilized by an individual pollen grain, making each apple seed genetically distinct! Similar to children carrying characteristics of both their biological parents, each apple seed will have characteristics from both the apple tree that provided the ovule and the apple tree that provided the pollen. 

 

For commercial producers interested in developing a new marketable cultivar (like the Honeycrisp or Cosmic Crisp apple), they intentionally cross two trees that have the characteristics that they are interested in maintaining in the offspring sapling — such as disease resistance, flavor, flesh texture, fruit coloring, etc. But because you can’t control the genes that end up in each apple seed, it’s a matter of time and patience to see whether the new sapling produces the kind of apple that you are looking for! As folks from Cosmic Crisp write, “It can cost over $10 million and 22 years to create a new apple variety”.

So coming back to our beloved neighborhood apple tree, if you wanted that exact type of apple at your new home, you would have to use the vegetative propagation strategy of grafting. Grafting is an age old propagation strategy that fuses together the living tissue (called the cambium) from two different trees. Scion wood (fruiting wood) is collected from the tree that you would like to propagate and is attached to rootstock (the dormant root system) of another tree.  

 

Often people select which rootstock they use to manage for things like disease resistance and hardiness, but also for size. Trees grafted onto dwarf  or semi-dwarf rootstock can often be kept to a manageable 6-15 ft with proper pruning, in comparison to the 25+ ft height of trees grafted onto standard size rootstock. However one consideration is that trees grafted onto dwarf rootstock tend to have a more limited root system, which can affect a tree’s stability and its ability to pull water and nutrients from the soil. 

Jordyn Egbert, City Fruit's Development Manager, holds two pots that have apple trees with freshly wrapped graft unions.
Image of rootstock sizes from Washington State University.

In addition to allowing us to propagate a beloved tree or commercially successful cultivar, grafting allows many different varieties of fruit to be grown on a single tree, like the 40 fruit Franken-tree that boasts several varieties of stone fruit from the Prunus genus including peaches, nectarines, cherries, and plums. This kind of multi-variety grafting can be very handy for the backyard gardener, who may have space for only one or two trees, but wants to be able to grow a variety of fruit.  However, the general rule is that apples need to be grafted onto apple rootstock, pear on pear, and stone fruit on Prunus compatible rootstock. Grafting has also been used in the environmental conservation and restoration world to conserve mango varieties in India, or to protect Italian olive trees or American chestnut trees from pests and disease!

 

So, interested in trying your hand at grafting or curious about where you can pick up a multi-variety fruit tree? There are many different grafting techniques that exist, and one’s choice of grafting technique will depend on factors like experience level, the thickness of scion wood and rootstock that you’re working with, timing of season (working during dormancy vs. when sap is running in the spring after trees awaken from dormancy), and whether you’re hoping to add new varieties to an existing tree (called top grafting) vs. bench grafting with a potted sapling. 

 

Fruit tree societies, such as North West Fruit Society in Mt. Vernon or Seattle Tree Fruit Society, can be great ways to connect with other fruit tree enthusiasts, learn about what folks are planting and growing, and exchange scion wood! Area nurseries can also be a great resource to learn about different fruit varieties and can have large selections of bareroot multi-variety trees. Some nurseries to check out might include Burnt Ridge Nursery & Orchards, Restoring Eden, Swansons Nursery, Raintree, and Skipley Farm…just to name a few! 

This year, City Fruit hosted two free beginner grafting workshops — one in partnership with New Start Community Garden (Shark Garden) at their orchard and another in collaboration with the City of Kirkland at McAuliffe Park! Together the workshops engaged 20 community members, with attendees learning grafting basics and strategies for both bench and top grafting. City Fruit hopes to host more grafting workshops next year in the spring and early summer in more places across the Greater Seattle Area — please email volunteer@cityfruit.org if you’re interested in hearing about when the next workshop will be scheduled!  Until then, happy grafting!