The Science of Grafted Fruit Trees
Have you ever wondered why you can't always grow a true-to-name fruit tree from planting seeds? Folks often ask if it's possible to take the seeds from an apple, plant them, and grow trees that yield the same exact type of apples the seeds came from.
Unfortunately, for most fruit trees*, this isn't quite how it works. To explain, we'll start by addressing the history contained in seeds and why it's more reliable to plant and grow grafted fruit trees.
*There are exceptions that tend to have very little variation even as seed-grown trees, like pawpaw seedlings and certain types of citrus.
Reproduction in Fruit Trees
We'll use apple trees for example here. Most apple trees are not self-fertile. This means they need another different apple tree blooming nearby (at the same time) to pollinate the blossoms that in turn become the fruit.
So, if you had a Honeycrisp apple tree, you would need a different apple variety, like a Golden Delicious apple tree, to pollinate it. From one tree to the other, the male flower parts' genetic material pollinates the female parts of the flowers (with the help of bees, wind, etc.). The end result is fruit development in both mature apple trees.
History is Contained in Seeds
This cross-pollination is sexual reproduction in fruit trees. Even if a fruit-tree variety is considered to be self-pollinating, it is still receptive of other pollen — and the seeds of its fruit end up with all the history from past generations of both parent trees. The results of cross-pollination occur in the seeds, not the fruit. This is why cross-pollination can occur in your fruit tree's flowers and not affect the color or appearance of the tree's developing fruit.
The fruit is merely a vessel for the seeds. The seeds are what carry a history of traits from the parent tree and its pollination partner(s).
That's a lot of potential, but it's also unpredictable. If you were to plant the seed from a Honeycrisp apple, the resulting apple tree and its future fruit may display characteristics from anywhere in its lineage. The tree or its fruit may be similar to Honeycrisp or they may be throwbacks from somewhere in its genetic history, but – because they came from seed – they will not become a true Honeycrisp apple tree or true Honeycrisp apples.
Grafting for Consistency
One dependable way to ensure that the desired characteristics are maintained in subsequent fruit trees is through grafting. Grafting involves taking a scion or bud chip cut from the desired parent tree (for example, a Granny Smith apple tree) and physically placing it onto a compatible rootstock. The variety and the rootstock are calloused, or grown together, as the tree heals. All suckers are removed from the rootstock, and the Granny Smith scion is allowed to grow into the new tree, thus maintaining its Granny Smith identity. This process is called "asexual reproduction". Since only one parent/variety is involved in this process, the grafted tree will be true-to-name — and a true-to-name tree bears true-to-name fruit.
Most of Stark Bro's trees are either propagated through grafting — by joining a scion and rootstock together — or through budding. Budding involves placing a single vegetative bud into the side of the rootstock and wrapping it with cellophane tape until it heals together. The results of grafting and budding are the same: a true-to-name tree.
A grafted tree is consistent and has a reliable history of characteristics. It has a track record:
- It blooms at a certain time.
- It bears fruit at a certain time.
- It has predictable traits like disease-resistance or cold-hardiness.
- Its fruit can be expected to be a certain size, quality, and variety.
See the consistency in size and shape of these grafted fruit trees?
With this in mind, I will always recommend you plant trees that were propagated through grafting or budding methods. It's worth the investment to know exactly what you're getting!
— Elmer Kidd, Stark Bro's Chief Production Officer (retired)
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