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Grafting Pawpaws

What Is Grafting?

Grafting is the process of joining two distinct trees together to form a tree with the roots from one tree and the branches/fruit of another. Descriptions of grafting first occur in Ancient Greek writings from 424 BCE, but scholars believe that the technique may have been employed in China as early as 2000 BCE.

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Why Are We Grafting?

Named varieties, referred to as  'cultivars' , of pawpaw have been selected because of their superior fruit quality or growth characteristics. Pawpaws, like many fruits, are not 'true to seed'. This means that saving and germinating the seeds from the fruit of a named variety will not result in seedling trees with the same genetics as the mother tree. This is the same reason why you are not an exact copy of your mother- your parents' genetics combined to create a unique individual. Even trees planted from seeds in the same fruit will all differ in fruit size, yield, and quality, just as siblings in the same family can be quite different from each other! 

A seedling tree of unknown or poor quality can be converted into a named variety that produces known, superior quality fruit through grafting. In other words, grafting is a tool to clone well characterized pawpaw cultivars. Pawpaw trees grown from seed may produce fantastic fruit, but they also might produce fruit that is average or below average quality. By grafting superior cultivars, you know exactly what fruit quality to expect and eliminate the risk that your pawpaw trees produce poor quality fruit.

Still have questions? Check out our Grafting Frequently Asked Questions (FAQs)

Getting to Know the Lingo

Let's familiarize ourselves with some of the basic terminology used by grafters:

Seedlings are trees grown from seed. Since pawpaws are not true to seed, seedling trees may bear little resemblance to their parents.

Cultivars are named varieties of pawpaws that have been selected from the wild or out of breeding programs for some specific quality, often fruit size or flavor. All cultivars are not created equal, so do your research to make sure you are selecting a high quality cultivar!

A scion is the piece of branch harvested from a cultivar that you wish to clone. Pawpaw scions are harvested in the winter while the donor tree is still dormant.

rootstock is the tree onto which the scion is grafted. Pawpaw rootstocks are typically trees grown from seed.

Grafting Essentials

Grafting Materials

Materials Needed for Most Types of Grafting:

Additional Materials Needed For Bark Inlay Grafting:

Optional Safety Gear:

Grafting Methodology

Grafting relies upon trees' innate ability to heal from wounds. Grafting success is largely determined by (1) proper cambium contact and by (2) preserving moisture in the scion.

The thin layer of cells just below the bark is called the cambium- the most important part of any graft is to make sure that the cambium of the scion is in contact with the cambium of the rootstock. It is essential that cuts in grafting be smooth and flat, as even small gaps between the two cambial layers will prevent proper healing in the graft. 

When a scion is cut from its parent tree, it immediately begins to lose moisture. Scion wood must be kept in a humid plastic bag in the refrigerator, and care must be taken not to leave scion wood in full sun during the grafting process. If a scion loses too much moisture, the buds will die and the graft will fail. To reduce moisture loss while the graft is healing, we use a wax based product called Parafilm M, which is wrapped around the entire graft. 

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Timing

Timing can be a critical components of grafting success. Scion wood is collected in the winter when the buds are dormant and kept in the refrigerator to keep the buds from breaking dormancy. When the dormant scion is grafted onto an actively growing rootstock, it will take a few weeks for the buds on the scion to sprout leaves. This lag time allows the graft union to form callus and heal without the scion losing precious moisture through transpiration in emerging leaves.

For pawpaws, the time to graft is in the spring (May or June) when the tree is actively growing. Days should be warm and sunny, take care to avoid grafting when high winds or rain are in the forecast.

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Bark Inlay Graft

A Project Pawpaw favorite! Use with large, established rootstocks for vigorous scion growth. Convert unknown, wild, or root sucker trees to named cultivars

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Modified Whip & Tongue Graft

A tried and true method for grafting when the scion and rootstock are of similar diameter. Results in a strong graft!

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Chip Budding

Use when scionwood is rare and every bud counts - used by the pros but beginners may have lower success rates.

Can be used when the bark is not slipping​ ​

Bark Inlay Graft

Overview

The bark inlay graft is a fantastic way for the beginner grafter to convert existing trees to named cultivars. When small farmers are planting orchards, we often recommend that they limit their risk by planting seedling trees rather than expensive grafted trees. Once the seedling trees are established, they can be 'top-worked' using the bark inlay graft. 

Modified Whip & Tongue Graft

Overview

The modified whip & tongue graft is a robust grafting technique that yields strong graft unions. This type of graft is best when the diameter of the scion wood closely matches the caliper of the rootstock. 

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Alternative: The Modified Bark Graft

Well known pawpaw nurseryman Cliff England uses a similar graft, the Modified Bark Graft, which is even simpler. He has great success with this method when bench grafting seedlings, making this another strong option for beginner grafters. Here is a video of him demonstrating the process.

Chip Budding

Overview

The chip bud is a great technique to use when scionwood for a variety is limited and you are confident in your grafting ability. Chip budding uses only one bud per graft, meaning that a single piece of scion can often be used for five or more grafts. This is one of the techniques used by large nurseries, however many beginners find that they have lower success rates using chip budding. 

Graft Aftercare

Late Summer/Fall

Grafting materials such as tape, rubber bands, and parafilm can often be romoved 4-6 weeks after grafting, once the graft union has healed and the scion is actively growing. Failute to remove these materials may cause the graft to become girdled and to die, a real shame if you've gotten this far!

Next Season

Make sure to periodically check your tree for suckers or water sprouts. Any growth originating from below the graft union will have the genetics of the rootstock, not of your grafted variety. To keep these sprouts from competing with your grafted variety, remove all growth that occurs below the graft union.

Remove any fruit that occurs on your grafted tree this season, as you want the energy from the rootstock to go into producing healthy vegetative growth instead of fruit. Additionally, the weght of fruit might put too much stress on the graft union which is still healing.

Congratulations!

You've not only grown yourself a new, grafted pawpaw tree, but you also learned a new skill. Many other species of fruit and nut trees can be grafted, and you can even graft some garden plants such as tomatoes! Feel free to experiment, refine your skills, and most importantly to have fun!

Knowing how to graft also gives you the ability to change the variety of tree you are growing by using the bark inlay graft to topwork your trees. Some day down the road, you may decide that you would like to try a different pawpaw variety. If that happens, be sure to check back here to see if Project Pawpaw has released any new varieties! You can also sign up to hear about the progress we make in our research and pawpaw breeding efforts. We'll only reach out twice a year!

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  • Why do we need new varieties of plants?
    New plant varieties play a pivotal role in addressing agricultural challenges. They enhance crop productivity, combat pests and diseases, adapt to changing environmental conditions, and contribute to economic prosperity. Additionally, new varieties may taste better, last longer, or be healthier than existing varieties, making them indispensable assets for farmers and consumers alike!
  • How do you breed new varieties of plants?
    We can create new plant varieties by doing the same thing that humans have been using for thousands of years - finding the best plants and saving their seeds! Plant breeders start by selecting individual plants that have superior characteristics and allowing them to pollinate each other. The resulting seeds from that pollination, or 'cross', display a combination of the traits of each parents. Breeders then grow those seeds into plants and examine each one to find an indivual with the best combination of traits from the parents. When a plant is found that has great flavor, quality, yield, and growing characteristics, breeders may decide to release it as a named variety. In a crop like pawpaw, that means grafting a branch from our new variety onto the roots of seed-grown pawpaw seedlings and distributing them to growers and gardeners.
  • Where does the funding for Project Pawpaw come from?
    Project Pawpaw is funded by the people, for the people! 100% of proceeds from the sale of merchandise and seedlings go towards supporting research and breeding objectives. We're also in the process of applying for grant funding to help us take on bigger, more ambitious projects!
  • Will these new varieties be GMOs?
    Nope! We'll be using traditional plant breeding, just like humans have been doing for thousands of years! Here is how we do it: 1) Choose one parent that has desirable traits and allow it to pollinate another parent with desirable traits to make a fruit 2) Grow the seeds from that fruit into trees and screen through the offspring to find individuals that have the best combination of traits from the parents 3) Repeat this many times, until you find a tree with all of the traits you are breeding for! 4) Distribute scionwood or grafted trees of your new variety to farmers for field trials in different environments, and then (hopefully) distribute to growers and gardeners
  • When will new varieties be released?
    Thats a tough question. To breed a new variety of apple, it typically takes about 15 years in an etablished and well funded program. We are starting from scratch, but we also have the advantage of being able to use some modern tools and technology to speed things up! While we work on breeding the next big pawpaw variety, we'll be sharing results from our research projects about the best ways to grow, harvest, and store pawpaws as well as working with other organizations to develop a market for pawpaw fruit and give growers the tools they need to be sucessful. It's a long process, so we'd better start now!
  • How many trees do I need to plant to get fruit?
    While some varieties of pawpaws may be self-fertile, we recommend planting at least two genetically distinct trees. This can be accomplished by planting two seedling trees or by planting two grafted trees of different varieties. The underlying genetic basis of this "self-incompatability" is poorly understood, but we are excited to learn more about it in our research!
  • What's the difference between seedling and grafted trees?
    Seedling trees: Seedling trees are grown from seeds, either from naturally pollinated trees or through intentional cross-pollination. These trees exhibit natural genetic variation, meaning each tree may have different traits just like how human siblings are each a little bit different from each other. This can lead to a diverse population of trees with varying characteristics. Grafted trees: Grafted trees are created through a process called grafting. This involves joining a desired tree variety (known as the cultivar) onto a rootstock of a different tree. Grafting allows for the propagation of exact genetic replicas of the desired cultivar. The resulting tree inherits the traits of the cultivar while utilizing the root system of the rootstock. The key difference is that seedling trees show natural genetic variation, while grafted trees maintain the specific traits of the cultivar they are grafted from. Grafted trees are often preferred when consistent and predictable traits, such as fruit quality or disease resistance, are desired. Seedling trees, on the other hand, offer a wider range of genetic diversity.
  • Can pawpaws be planted in full sun?
    While pawpaws grow and yield best in full sun, they will tolerate partial or full shade but will grow with less vigor and will produce fewer or smaller fruits. The most important thing here is timing! If a seedling has been grown in shaded conditions, it must be kept shaded for the remainder of that season. For this reason, we recommend planting pawpaw seedlings in tree tubes for the first growing season. The tube can then be taken off in the early spring before the tree has emerged from winter dormancy, at which point the pawpaw tree will be able to tolerate full sun.
  • Do pawpaws cause Parkinson's Disease?
    Pawpaws have been eaten by people in North America for thousands of years. The misconception that pawpaws may be linked to Parkinson's Disease stems from the fact that pawpaws produce a class of compounds called acetogenins. Acetogenins are found in many plant species, including several food crops around the world. Some acetogenins found to have neurotoxic activity have been associated with a rare neurological disorder called atypical parkinsonism. However, it's important to note that the levels of annonacin in pawpaw fruits are generally low and consuming pawpaws as part of a balanced and seasonal diet is considered safe. Initial studies suggesting the link between acetogenins and Parkinson's disease cited higher rates of atypical parkinsonism in populations of island dwelling people who consumed tea made from the leaves of the soursop tree as a regular part of their diet. These people exhibited a population-wide rate of atypical parkinsonism slightly higher than people in other areas, however this trend could also be atributed to genetic or environmental factors not accounted for in this study. We'll be selecting new pawpaw varieties with little or no acetogenin content out of an abundance of caution!
  • How many years until my pawpaw seedling bears fruit?
    The time it takes for a pawpaw seedling to bear fruit can vary. Typically, it takes around 4 to 7 years for a pawpaw seedling to reach maturity and produce its first fruits. However, the exact timing depends on various factors such as growing conditions, climate, and the specific cultivar of the pawpaw. It's important to note that pawpaw trees are known for their slow initial growth, but they can become productive and provide a bountiful harvest once they reach maturity. So, patience is key when waiting for your pawpaw seedling to bear fruit!
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