Seedling vs. Grafted Trees

In today’s market, all commercial chestnut 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.

 
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Commercial chestnut planting, utilizing improved cultivars for maximum yield. 
 
Benefits of using cultivars compared to seedling trees
  • Cultivars are predictable in performance (e.g., harvest time, pollen production, nut size).
  • Grafted cultivars are mature when planted and therefore initiate nut production in Michigan much sooner than seedlings.

  • Since cultivars are mature, they usually drop leaves at the appropriate time in the autumn.

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 5 years.  This earlier production allows growers to recoup their establishment costs and start generating revenue more 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 which 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 and the fact is that 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.
 
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 fall fresh from the tree. But given 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’ has a much better taste. In fact, grafted ‘Colossal’ chestnuts have been some of the most sought after chestnuts on the market due to both 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. 

Different chestnut species

Generally, there are three species of chestnut that contribute to the genetic makeup of chestnut trees planted in orchards. The species from which cultivars have been selected are those that have a long history of chestnut cultivation, including the Chinese chestnut, the Japanese chestnut (and its subspecies, Korean chestnut) and the European chestnut (Castanea mollissima, C. crenata, and C. sativa, respectively). Some of today’s cultivars are actually hybrids or crosses among these three species. The species can appear similar looking at first, after all they are all edible chestnuts, but using differences such as leaf shape, leaf hairs, stem anatomy and nut characteristics, one can soon begin to tell them apart. Certainly, the hybrids between these trees are difficult to tell apart from the parents that helped form them. Today, we rely on DNA analysis to tell the species and cultivars apart with accuracy.

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