Propagation of Some Aged Bonsai Plants

The Arnold Arboretum bonsai, some of the oldest and largest specimens of bonsai in the United States, were imported more than half a century ago. Through the years changes have taken place in the characteristics of the plants, and early in 1969 it was decided to have a program of renovation. The ensuing alterations of Chamaecyparis pisifera ’Squarrosa’ (Moss cypress) and the C. obtusa cultivars (Hinoki cypress) led to the removal of excess parts which provided propagating material. Ordinarily propagation of these subjects would have been done in autumn, but pruning the bonsai took place in March so the cuttings were processed at that time.

Chamaecyparis pisifera ’Squarrosa’ (Moss cypress). A Fixed Juvenile. When plants are grown from seeds, characteristics which ap- pear on the young seedlings often differ greatly from those which are found later in the plant’s life. In the case of conifers, the first or juvenile growth is gradually replaced by mature growth thereby leading to a normal plant. The interval between the advent of maturity and the time of flowering and fruiting has been termed the "adolescent phase". These stages represent the normal course of events in the development of conifers. However, in some conifers particularly in the genera Chamaecyparis and Thuja the juvenile to adult transition may fail to take place and some plants remain in the juvenile phase. These have been termed "fixed juveniles". Plants which remain physiologically juvenile also retain a trait associated with the seedling stage - the ability to root readily. Chamaecyparis pisifera ’Squarrosa’ is a fixed juvenile. The cuttings taken from our 75 year old bonsai plant, which is 30 inches tall, rooted easily. When propagating conifers at the Arnold Arboretum cuttings of large size are preferred. Figure 1 illustrates plants which arose from rooted cuttings of our 75 year old C. pisifera ’Squarrosa’. They have grown but little since being potted and the multi-branched framework which is evident was present when the cuttings were made. Each cutting consisted of at least several years’ growth. Thirty cuttings were divided into two equal lots. These were inserted in a polyethylene plastic propagating chamber. A 297 298 medium consisting of one-half sand and one-half Perlite was used. Lot # was treated with a root-inducing substance con- taining 0.8% indolebutyric acid in talc with the fungicide Thiram added at the rate of 15%. Lot #2 was treated with a liquid formulation of indolebutyric acid plus napthalene acetic acid at the rate of 5,000 ppm each. In both cases 87% of the cuttings produced excellent root systems. Chamaecyparis obtusa (Hinohi False Cypress) Seven unnamed cultivars of Chamaecyparis obtusa from the original Larz Anderson gift are in the Arboretum’s bonsai col- lection. They range in age from 105 to 230 years. When raised from seeds Chamaecyparis obtusa has given rise to numerous dwarf and slow growing forms. The Arboretum’s bonsai plants are not typical of the species and must have originated as seedling mutations or from propagules of such mutations. Figue 2 shows rooted cuttings of Chamaecyparis obtusa which were started in March of 1969. They, too, were made from multibranched cuttings consisting of several years’ growth. The following table shows two methods by which the cuttings from three plants were treated together with percentages of success.

ALFRED J. FORDHAM 299

Fig. 1. Plants of Chamaecyparis pisifera ‘Squarrosa’ propagated from a 75-year-old bonsai. The multi-branched framework which is evident was present when the cuttings were made. Photo: Alfred J. Fordham.

Plants of Chamaecyparis obtusa var. rooted from multi-branched cuttings consisting of several years’ growth. Photo: Alfred J. Fordham.