Trunk cross-sectional area was found to bear a linear relationship to total above-ground weight of apple trees. From these data, it is suggested that trunk measurements can be used to estimate the potential bearing surface of any orchard tree as long as it has not been pruned heavily to prevent crowding. This relationship permits the calculation of yield efficiency as fruit weight per cm2 trunk cross-section. Estimates were made of maximum bearing surface potential (tree weight) per acre (as cm2 trunk area) for several kinds of tree fruits and nuts.
The Mugo or Swiss mountain pine is one of the most popular evergreen shrubs for modem landscaping. Mugo pines include the type species (sometimes referred to as var. mugo or var. mughus) and 3 additional geographical varieties pumilio (Haenke) Zenari, rostrata (Ant.) Gord., and rotunda (Link) Gord. (1, 8). The most desirable dwarf forms for landscape use are derived from p. mugo var. pumilio. The other 2 botanical varieties are usually of arboreal size.
‘Thompson Seedless’ grapes (Vitis vinifera L.) were trained to heights of 1.4, 1.7, and 2.0 m with and without an 0.6-m crossarm. Data were collected from 4 seasons beginning in 1969. Within treatments variability was usually too great to reveal significant differences among treatment means for most parameters measured within a single year. Analysis of the 3-year combined results revealed that the highest trellis resulted in most yield, most clusters, and most berry sugar per vine. Vines on the lowest trellis had the least pruning brush wt. Vines with crossarms had higher wt per berry, soluble solids, sugar, and wt brush per vine than did vines without crossarms.
Tests in 11 plots of ‘Italian’, ‘Early Italian’, and ‘Brooks’ prunes showed several influences of rootstock on tree growth, flowering, yield, fruit size, maturity, and quality. Of the 6 Prunus species represented by the 19 rootstocks tested, myrobalan roots usually resulted in larger trees, heavier bloom, but lower yield efficiency than did peach roots. Trees on Marianna and several P. domestica L. roots varied in size and yield, but most of them had greater bloom density than trees on peach root. ‘Italian’ fruit firmness varied inconsistently with rootstock. ‘Early Italian’ fruits were firmer on peach than on other roots, but ‘Brooks’ fruits were less firm on peach than on other roots. The tendency for internal fruit browning of ‘Italian’ was greater on plums than on peach roots. Other fruit maturity and quality factors varied by cultivar and by individual rootstock. Fewer trees on peach root died from trunk canker (Pseudomonas syringae van Hall) than did those on several clonal plum roots, but some plum-rooted trees outgrew the canker and survived as well as trees on peach stock.
Growth and yield of ‘Montmorency’ cherry varied greatly both within and between species of rootstock clones. Trees on FI2/1 mazzard (Prunus avium L.) were very vigorous and less productive than those on other stocks. Some growth control was found within each species or hybrid group but was most pronounced with P. mahaleb L. clones PI 193688, PI 163091 and PI 193693. Yield efficiency was not necessarily related to tree size but tended to be better with smaller trees. The 3 P. mahaleb clones listed above and the vigorous clones OCR-3 (P. mahaleb × P. avium) and PI 194098 (P. mahaleb) had high yield efficiencies. Trees on F12/1 and P. mahaleb PI 193703 had the lowest yield efficiencies. Based upon ideal orchard spacing for tree size, calculated annual yields exceeded 10 metric tons per ha for 6 of the clonal stocks.
‘Golden Delicious’ and ‘Starking Delicious’ apple (Malus domestica Borkh.) on Mailing 9 (M 9) rootstock were planted in 1956 in alternate rows 4.57 m (15 ft) apart, with in-row spacings of 1.22, 1.83 and 2.44 m (4, 6, and 8 ft). Average annual yield was higher at the closest spacing (1794 trees/ha) during the entire 18 years of the test. The pattern of yield was similar for the 2 cultivars but was higher for ‘Golden Delicious’ because of the lower fruit set of ‘Starking’ in some years due to adverse weather. Pruning during the last 6 years of the test was done by mechanical shearing of tops and sides, with no detailed pruning within the fruiting wall. This type of pruning on dwarf trees resulted in adequate fruit size, color, and quality with normal fruit thinning practices.
Plantings of the ‘Italian’ prune (P. domestica L.) were established on seedling peach (P. persica L. Batsch) and clonal Myrobalan 29-C, B, 2-7 (P. cerasifera, Ehrh.); Marianna 4001, 2623, 2624 (P. cerasifera × Munsoniana?, Wight and Hedr.); and St. Julien A (P. insititia L. Bullace) rootstocks in 7 orchard sites in Oregon. Leaf samples were collected in the years 1968 to 1970 and analyzed for element content. Trees with plum rootstocks had greater leaf N, K, Mn, and Zn and slightly less B and Mg than those on peach. Plum clones, Myrobalan 29-C, Myrobalan B, and St. Julien A, were more efficient in the uptake of Ca. There were positive correlations between N and Ca, N and Mg, N and B, N and Zn, Ca and Mg, Ca and B, and Mg and B for most of the stocks. There was a negative correlation between K and Mg for Myrobalan 2-7 and the 3 Marianna clones. Myrobalan B and Marianna 2623 and 2624 had a negative corrleation for K and Ca whereas St. Julien A had a positive correlation.
Recent interest in the production of Rhododendrons as potted plants has raised many questions concerning propagation, dormancy, flower initiation, and general patterns of growth and development. Cathey (1) has shown that general growth habit may be altered to give a more compact plant through the use of Phosphon or by B-nine. He found further that flower initiation could be stimulated after the production of 4-5 flushes of growth instead of the normal 8-9 flushes required under natural conditions, thus making this plant useful as a potted plant. Myhre (3) showed that large applications of phosphate fertilizer increased the number of terminal apices initiating flowers in ‘Cynthia’. In 1920, work in the Netherlands by Luyten and Versluys (2) indicated that leaf and flower initiation occurred early in the growth cycle, May 31 to June 8.
The physiology of dormancy in Lilium longiflorum ‘Ace’ was studied by determining the relationships between plant growth and composition and treatments such as bulb scale removal, cold treatment, field soil heating and chemical stimuli. Initiatory activity was continuous in the daughter bulb until its anthesis, but elongation of daughter axis leaves and internodes were normally inhibited until autumn. Inhibition of the daughter axis was high during the spring prior to anthesis of the mother, but progressively decreased following anthesis and disappeared completely by autumn. Balances of inhibitor-promoter growth substances were found in the bulb scales. Daughter scales were found to be the principal source of inhibitors. Treatments conducive to breaking dormancy included 40°F storage, GA3 treatment and field soil heating in early spring. Dormancy-breaking cold treatments were followed by changes in nitrogenous substances characteristic of dormancy removal in other species. The period of dormancy in the daughter portion of the lily bulb is of the correlated type and involves scale inhibition of axis elongation rather than initiatory activity in the apex.
Response of cold-treated ‘Nellie White’ Easter lily bulbs to various degrees of scale removal, ranging from 0 to 100%, showed that scales can perform inhibitory and promotive roles at various times. The scales were not necessary for flower induction, but the number of leaves and flowers initiated was proportional to the number of scales retained. Daughter scale removal accelerated daughter sprouting by increasing internode elongation, but subsequently reduced the rate of organ formation and expansion. Daughter scale removal reduced the number of leaves and flowers initiated and anthesis was delayed because of the reduction in rate at which these organs expanded.