To give complete details of several years' work would take more time than is feasible here. Circular 87, Growing American Holly from Cuttings—Cold Frame Method, obtainable from the Mailing Room, West Virginia Agricultural Experiment Station, Morgantown, West Virginia, gives construction details of a suitable bottom-heated cold frame. However, with chestnuts, natural shade was not used and half of the sunlight was excluded. An article in the October issue of The National Horticultural Magazine—"Rooting Chestnuts from Cuttings"—outlines procedure and results through 1952.
In this paper I will present a resumé of our experiences and observations. Our facilities were limited so that the number of cuttings set in each case was very small. Percentages of failure or success should be taken as indicative only.
In the propagation experiments, preliminary observations were made by placing softwood cuttings in a bottom-heated cold frame at intervals during the growing season. The soil medium was two thirds washed sand and one third peat moss. Daily watering was by a hand hose. The root-inducing substance was indole-butyric acid crystals in a talc based mixture, one to one hundred. The results were completely negative.
The next season a small cold room was constructed in which conditions thought to be desirable could be maintained. Air temperature was kept at approximately 65° F., fog nozzles were operated continuously except for an occasional airing of the cold room, and about 200 foot candles of white fluorescent light were delivered upon the rooting surface. The rooting medium was white, washed, building sand placed over one half inch of sphagnum moss. The moss, in turn, had been laid in a rooting bench with a hardware cloth bottom exposed to the air. The interior air circulation was maintained by an electric fan operating day and night. The soil temperature was held at 70° F.
Cuttings were taken at intervals throughout the season and their basal sections soaked in a water-based solution of indole-butyric acid crystals at concentrations varying around 60 parts per million. During a 70-day period roots were formed on cuttings taken in June, July, and August. Among the successful cases the poorest result was 66-2/3%, and the best was 100%.
The young plants were fed nutrient solution and later transplanted to a light, sandy soil within a bottom-heated cold frame. Some roots were dead at the time of transplanting, burned, perhaps, by the nutrient solution. The soil temperature within the cold frame was maintained at 70° F. until late in the fall, and then the plants were hardened by reducing the water content of the soil medium and lowering the temperature. All of the plants were dead when they were inspected in March.
The next year a bottom-heated cold frame was equipped with fog nozzles. The soil medium was white, washed, building sand. Softwood cuttings, treated the same as the previous year, were inserted on August 20. Cuttings from juvenile American chestnut seedling trees, juvenile Chinese trees, and mature Chinese trees were used. Within a 70 day period heavy root systems were formed on 54-6/11% of the cuttings from the juvenile Chinese trees, 50% from mature Chinese trees, and 20% from juvenile American trees. No nutrient solution was applied, the young plants were transplanted to a sandy soil in another cold frame, were hardened as during the previous year, but the soil medium was not allowed to freeze during the winter. In April the plants showed well-formed terminal buds starting to swell and turn green. Some were transplanted into pots and placed in the greenhouse; others were transplanted into a light soil in a lath house. All died subsequent to transplanting. Inspection of the roots showed severe breakage. It was concluded that repeated transplanting had been fatal, and that in the future cuttings would be rooted in plant bands or pots and transplanted only once.
It is too early in the current season for accurate results to be recorded. However, modifications have been tried and observations made. These are presented here in outline.
Type of cutting:
a. Cuttings with soft, growing tips will apparently root more quickly than hardened shoots, but the leaves tend to turn brown and the plant dies. Conversely, cuttings from short, lateral growth, well-hardened, will retain their leaves better and eventually show a higher percentage of success.