A few months ago I saw this response to a readers question about vegetative propagation by Hill Craddock at the University of Tennessee, which I reproduce here with his permission. As a detailed decription of his experiences I thought it a valuable resource that should get greater distribution. If you have experience with vegetative propagation or grafting with American chestnut please leave a comment about your experiences.
Bill Adamsen
Chestnuts are difficult to root from cuttings. In my experience, certain types never rooted. In general, Japanese and hybrid cultivars rooted, while European and Chinese cultivars did not. I have no experience with American chestnut.
The kinds of problems encountered while trying to root chestnut cuttings include rooting inhibitors in the stem tissues (endogenous factors which must be removed before adventitious roots are formed), the physiological age of the stems (seedling and juvenile stems root more readily that sexually mature stems), the hardness of the wood and timing of the cuttings (hormone levels need to be adjusted – softwood cuttings in early summer may require less rooting hormone than hardwood cuttings taken later in the summer; and fully dormant shoots collected in winter almost never root).
Attempts to overcome the list of problems have included techniques such as soaking the cuttings before sticking (to leach out inhibitors), collecting from near the base of the tree rather than from the crown (because shoots arising from near the root system are physiologically immature), wrapping shoots in light-proof barriers (etiolated shoots may more readily form adventitious roots), repeated grafting and re-grafting onto seedling rootstocks to rejuvenate the “adult” material, hormone pre-treatment of shoots before cutting, etc. Tip cuttings from week-old seedlings may, in fact, be very easy to root (however, one has to question the utility of multiplying seedling material).
Consequently, virtually all of the word's chestnut cultivars are propagated by grafting. The only exceptions that I know of are for a few Euro-Japanese hybrids grown from tissue-cultured micro-cuttings in a process patented by INRA (Bordeaux, France), and a very few other types grown from stool-bed layering. These own-rooted plants are mostly used for rootstocks.
Tissue-cultured shoots, by the way, face a similar set of problems with the additional difficulty of hardening off the micro-cuttings even when they do (rarely) root!
Some chestnuts can be coaxed into forming new roots by layering. Simple layers and stool-bed layers were used commercially during the 1970s and 1980s in Italy and France to produce own-rooted cultivars of some of the Euro-Japanese hybrids. But, the stool beds that I know of have mostly been
abandoned.There is a large body of literature on the rooting of (and the failure to root) chestnut cuttings. I have some of the references. If you are interested, please write to me, and I will try to locate the papers.
Hill Craddock
