Chestnut Seedlings or Grafted Cultivars: What Are the Differences?

Don't plant seedling trees in Michigan. No matter what you hear, see or read on the Internet. If you are a commercial grower in Michigan you cannot afford to plant seedling trees. I still see ads and still hear about a few growers establishing chestnut orchards with "seedling" chestnuts. This is such a waste! A seedling tree is not defined by size or age, but by the fact that it was never grafted. Would you establish a cherry, peach, or apple orchard by dropping a pit or seed into the ground and waiting for the tree to grow? NEVER! Maybe 100 years ago. Today, all commercial fruit and nut tree orchards are established with cultivars that have been selected by experts for various traits. These cultivars are not produced through seed, but are cloned by grafting/budding onto the stems of seedlings that will support the chosen cultivar. In this manner, a single tree can be copied millions of times by simply cutting small branches from the chosen tree and attaching it onto the stem of established seedlings. The branch that is cut from the chosen tree is called the scion wood and the tree that it is attached is called the rootstock. The rootstock will be from a seed that was planted for the purpose of grafting. If you purchase a seedling and promise yourself you will graft it, please re-consider. Most people never take the time or have the impetus to graft the trees and you will soon find yourself in a situation where your orchard is producing less than 10 percent of what it could have produced and you will not be a commercial grower.
Please do not plant seedlings in Michigan. With seedling trees, less than 50 percent of the trees will go into production in any given year and of those, only 10 percent will be worthy of your resources, in terms of fertilizing, irrigating, and harvesting.

Please do not plant seedlings in Michigan. It will take the trees 8 to 12 years to go into production because physiologically, the trees need to go through seedling and juvenile stages, which can take many years. Grafted trees are normally considered mature trees no matter how young, and can be in production 2 to 3 years after planting.
If you plant seedling trees, consider yourself fore-warned. What I wish to impress upon you is the term "cultivar." A cultivar is almost always reserved for genetic material with certain identifiable features or traits that can be copied or cloned by grafting to produce identical copies. Probably the most well known story is the 'Naval' orange. A mutation from a seed bearing orange, the 'Naval' orange was found and it did not produce seed. The scion from the navel orange was grafted to rootstock and sent to California where the original grafted tree supporting the original scion can still be viewed (called the 'Washington Naval' orange tree) in Riverside, California.

There are several methods to attach scion wood to rootstocks and some methods may work better than others for different tree species or under different conditions. For example, budding is a type of grafting where just the bud from the chosen tree is placed within the bark of the rootstock. The scion in this case would be the bud. Chestnuts are commonly grafted with scion wood or with buds, but in either case, the scion will produce trees identical to each other. Once the scion's bud has sprouted and produced substantial growth, the rootstock above the point of scion attachment will be removed so the scion becomes the only growing material above the point of scion attachment.

If you are following the ideas presented so far, then you will realize that planting seeds will produce the rootstock to which the scion is attached and one rootstock will be genetically different from any other rootstock. Therefore, even if the scion is the same throughout the orchard, the rootstock will be genetically distinct from tree to tree. This is one reason why trees planted in an orchard will still show some variability. The genetic diversity of the rootstock can be ignored in most situations, but there have been several cases where rootstock variation has lead to problems as minimal as bark discoloration or as serious as graft union failure and early tree death. In plant systems that have been studied for several decades, the knowledge of rootstock and scion wood combinations can lead to important orchard management opportunities such as rootstock that can lead to the preferential dwarfing of scion growth or resistance to soil-borne root diseases.

We are far away from that level of genetic management in chestnut, but we do believe that fewer problems will develop when the rootstock and scion wood are genetically related. If this theory holds true, then Chinese chestnut varieties should not be grafted to European or American chestnut and vice versa. That does not mean you can't do it or shouldn't try it in experimental situations, but it does mean that unless further research points a new direction, commercial orchards should be established with trees produced by closely related rootstock and scion wood.

Benefits of Using Cultivars When Compared to Seedlings

1. Cultivars are predictable in performance (even if not now, they will be once you learn more about them).
2. Cultivars are mature when planted and therefore produce nuts sooner than seedlings.
3. Cultivars are mature and usually drop leaves at the appropriate time in the autumn (seedlings are immature and hold onto leaves well into winter which can accumulate snow and break the limbs).
4. Cultivars can be placed in the orchard based on their predicable characteristics (e.g., harvest time, pollen production, size).
5. With a cultivar, you can talk about the traits you like and don't like and the discussion is meaningful since you can talk someone into purchasing or out of purchasing a particular cultivar. There is knowledge in discussing cultivars.
6. Every tree you plant in the orchard, when planting specific cultivars, should perform the same way in the orchard (see number 1, above).

Deterrents to Using Cultivars

1. Cultivars are expensive. They seem expensive, at first, because they cost more than seedlings (not always), but you should recover this in the first years of production (see number 2 in Benefits, above).
2. They die. Cultivars can die, but not as often as seedlings trees not producing nuts for many years or ever. More than 50 percent of the trees in a seedling orchard do not produce nuts. Researchers and nurseries continue to work on methods of keeping trees alive after planting such as using more robust root stock.
3. They get chestnut blight. That depends on the cultivar. You can plant cultivars that are completely resistant to chestnut blight. Many of the seedling trees for sale at nurseries right here in Michigan are chestnut blight susceptible—even if Chinese—because some of these Chinese chestnut seedling trees had American chestnut father trees. If someone is selling Colossal-seedling trees, they are selling you chestnut trees with unknown predictable behavior AND they will be blight susceptible. Why would you purchase this for an orchard?
4. They don't taste good. Again, this is a case of mis-information. This is probably referring to tasting nuts from the cultivar ‘Colossal’ right from the tree.  When a ‘Colossal’ grafted nut falls fresh from the tree, it usually does not taste as good as a Chinese (grafted or ungrafted) nut that falls fresh from the tree.  But given a couple of weeks in refrigeration, the process of curing begins and the starches begin to turn to sugar. Grafted ‘Colossal’ chestnuts have been some of the most sought after chestnuts in the local grocery stores due to size and taste, combined.  In a Missouri taste test, it was considered one of the sweetest nuts.