Improved chestnut cultivars are a sound investment

Utilizing improved grafted chestnut cultivars is critical to economic sustainability for Michigan chestnut growers.

Orchard of grafted chestnut cultivars in Michigan. Photo: Erin Lizotte, MSU Extension.
Orchard of grafted chestnut cultivars in Michigan. Photo: Erin Lizotte, MSU Extension.

In today’s market, all commercial fruit and nut tree orchards should be established with cultivars that have been selected by horticulturalists for superior qualities. These cultivars are not produced through seed, but are cloned by grafting or budding onto seedlings that will support the chosen cultivar. In this manner, a single tree with beneficial traits can be copied millions of times by simply cutting small branches from the chosen tree and attaching it onto the stem of planted seedlings. Conversely, seedlings are the result of sexual recombination between a known mother tree and an unknown father, resulting in endless variability and unreliable characteristics, making them suboptimal for commercial production.

There are many benefits of using grafted cultivars compared to seedling trees. Cultivars allow growers to consider and select for specific traits based on grower needs and goals. Cultivars are predictable in performance and can be selected to optimizing production. Important characteristics that may help a grower select between cultivars include harvest time, pollen production and nut size, all of which are unknown in seedling populations.

Grafted trees also come into bearing much earlier. Regardless of their size or age, grafted cultivars are mature when planted and therefore initiate nut production immediately with substantial yields within five years. This earlier production allows growers to recoup their establishment costs and start generating revenue quickly. With seedling trees, it is well known that many trees do not go into production for many years if ever. This means that the fertilizers, pesticides, irrigation, etc. given to non-productive trees in the seedling orchard are wasted resources, costing money and compromising the environment with little or no return.

Additionally, since cultivars are grafted from mature tissue, they usually drop leaves at the appropriate time in the autumn and are less prone to related winter injury. Young seedling trees have a tendency to hold onto leaves well into winter, which can accumulate ice and snow that can break limbs, further damaging productivity.

So why would anyone plant seedlings? The answer is simple: Cultivars are more expensive. However, the premium cost of grafted cultivars is recouped quickly through faster, increased and more reliable nut production. The chestnut cost of production has shown that growers producing superior chestnut cultivars can recoup their investment in as little as six years and have the potential to see substantial returns on their investment over time. Research has shown that seedling orchards produce far fewer nuts and take longer to begin bearing. It is impossible to create a representative economic model, as there is too much variability in the germplasm.

Despite advertising touting “superior seedlings,” there is no known method to predict the quality of chestnuts from seeds until they are mature. Most of the seedlings will not be superior. This is due to the shuffling of genes during the sexual crosses leading to the development of the seed. The only use for seedlings in a commercial orchard is as rootstocks for improved cultivars.

Another reason growers have not planted grafted cultivars is the belief they are more susceptible to chestnut blight. We know that chestnut blight susceptibility is tied to species and has nothing to do with the method of propagation. There are grafted cultivars that are completely resistant to chestnut blight, and conversely there are seedlings that are very susceptible to chestnut blight. Additionally, great strides have been made in managing chestnut blight in orchards; it is simply not an insurmountable issue. Like all pests, chestnut blight simply requires monitoring and timely management.

Finally, the last reason some may hesitate to plant improved cultivars is a misconception that they don’t taste good. This is probably referring to how nuts of the cultivar ‘Colossal’ taste right from the tree. A ‘Colossal’ grafted nut usually does not taste as good as a Chinese grafted or seedling nut that falls fresh from the tree. After a couple of weeks in refrigeration, which is expected in any commercial scale chestnut operation, the process of curing is completed and starches turn to sugar ‘Colossal’ and have a much better taste. In fact, grafted ‘Colossal’ chestnuts have been some of the most sought after chestnuts on the market due to size and taste. In a Missouri taste test, Michigan-grown ‘Colossal’ nuts were considered the sweetest nuts of the entire test, beating out Chinese chestnuts and other ‘Colossal’ nuts from California and Missouri.

To start out with the best possible plan for success, growers either establishing or expanding a chestnut orchard should include superior and improved chestnut cultivars. For more information on improved cultivars or other production information, please visit Michigan State University Extension’s Chestnuts page.

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