RESEARCH RESULTS FOR NURSERYMEN Kenneth C. Sanderson and William E. Barrick Department of Horticulture Horticulture Series No. 14 AGRICULTURAL EXPERIMENT STATION AUBURN UNIVERSITY Container Media and Fertilization by Kenneth C. Sanderson Department of Horticulture Nature of Work Objectives of this experiment were: (1) to emmpare processed garbage and imported peat moss-amended media in container plant production, and (2) to de- termine the best fertilizer treatment for plants grown in these media. Potted liners of Ilex cornuta 'Burfordi', Thua occidentalis, and Viburnum burkwoodi were transplanted into one gallon cans containing either soil, perlite and peat or soil, perlite and processed garbage. Fertilizer treatments consisted of (1) constant 150 p.p.m. N, 60 p.p.m. P and K; (2) bi-monthly fertilizer 1 oz per 3 gal 25-10-10; (3) 12 g Agriform tablet 14-4-6; (4) 1 oz Eeesy-Gro packet 16-8-16; (5) Mag-Amp 7-40-6; (6) Osmocote 18-9-9; (7) Osmocote 14-14- 14; (8) 8-8-8 inorganic; (9) Sta-Green 12-6-6. Dry granular fertilizers were applied at the rate of 3/4 lb per bu. Data on plant dry weight, height, and spread were statistically analyzed. Only statistically significant results are reported. Results Dry weight and height of plants in garbage-amended media were greater than those grown in peat-amended media. Constant and bi-monthly fertilizer applica- tions produced plants with the most dry weight. Mag-Amp and 8-8-8 produced shorter plants than constant bi-monthly and Osmocote 18-9-9. Spread of plants fertilized with constant and bi-monthly exceeded the spread of plants fertilized with Mag-Amp, 8'8-8, and Sta-Green. Constant or bi-monthly in either media produced plants with the most dry weight and differed from other fertilizer- media combinations. Constant, bi-monthly, and Osmocote 18-9-9 in either media 1. and Agriform tablet and Eeesy-Gro packet in garbage-amended media produced the tallest plants. Constant and bi-xonthly in both media produced plants with the greatest spread. Pubictios:l None at the time of this writing. Annual progress reports are available from the author. 2. Effects of Photoperiod and Temperature on Azalea Shoot Development by William E. Barrick and Kenneth C. Sanderson Department of Horticulture Nature of Work Effects of photoperiod and temperature on shoot development in azalea cul- tivars, 'Kingfisher', 'Red Wing', 'Roadrunner', and 'Red American Beauty', were studied under both controlled environment and greenhouse conditions at Auburn University from December, 1968, to March, 1970. Objectives were to determine if photoperiodic and temperature treatments applied after shearing affected shoot length, number of shoots per lateral branch, number of leaves per shoot, and dry weight per shoot. These measurements were recorded as indicies of desirable plant quality. Results Plants grown under increased photoperiodic treatments generally tended to have increased shoot lengths, decreased number of shoots, no differences in num- ber of leaves, and increased dry weights. Plants grown in low temperature (75- 65 0 F) chambers generally tended to have greater shoot lengths, higher number of shoots, more leaves, and decreased dry weights. This research might be appli- cable in formulating cultural practices for commercial production of greenhouse forcing azaleas. Since the number of shoots tended to decrease with increases in photoperiod, it might be feasible to reduce the daylength during the period of shoot break. After shoot break occurs, light could be applied to increase shoot length. Lighting might be applied as an extension of natural daylengths, rather than as "light break" treatments. A reduction in daylength could be used for an opposite effect, a reduction in shoot length. Temperature control could be beneficial in cultural practices; 75-65'F appeared an ideal temperature for shoot development in greenhouse forcing azaleas. Continued research is needed in this area. Effect of photoperiod and temperature seemed to be most critical during the period of shoot break. Additional experiments using dif- ferent photoperiod and temperature combinations to determine optimum conditions for maximum shoot break could be conducted. Publications: Barrick, W. E. 1970. Effect of photoperiod and temperature on shoot de- velopment in greenhouse forcing azaleas, Rhododendron cv. Masters Thesis. Auburn University. Sanderson, K. C., W. E. Barrick, W. C. Martin, Jr., and R. L. Self. 1969. Research Results for Flower Growers, Azalea Studies 1966-69. Hort. Ser. No. 13. Auburn University, Alabama Agricultural Experiment Station. Chemical Pinching of Azaleas With Ethrel and Offshoot-wO by Kenneth C. Sanderson ard William E. arrick Department of Horticulture N4ture of Work Ethrel, a new growth regulator, has been reported to exert a synergistic effect on the action of other growth regulators. Experiments were conducted on azaleas to determine the effect of Ethrel-alone and in combination with the chemical pinching agent, Offshoot-mO, on the number of breAks per shoot. One experiment was conducted on the cultivar 'Chimes' during September-October, 1969, and another experiment was conducted on the cultivar 'Kingfisher' during March-May, 1970. Treatments consisted of (1) hand sheared; (2) 200p.p.M. Ethrel spray; (3) 5,000 p.p.m. Ethrel spray; (4) 2,500 p.p.m. Ethrel plus 3.5% Offshoot-wO spray; (5) 5,000 p.p.m. Ethrel plus 3.5% Offshoot-mO spray; (6) 3.5% Offshoot-O spray; and (7) 4.5% Offshootsm0 spray. Sprays were applied to run off with a Halaby mist blower. Results A reddish discoloration of the leaves was observed on some leaves in both cuJltivars of Ethrel treated plants. Older, lower leaves fe U off both cultivars soon after Ethrel spraying. Plants usually recovered from leaf discoloration and produced new leaves after leaf drop. A combined spray of 5,000 p.p.m. Ethrel and 3.5% OffshootawO averaged the most number of breaks per shoot in 'Chimes' 3" plus 3.5% Offshoot-O. 'Chimes' and 'Kingfisher' had 2.9 and 2.6 breaks, re- spectively, when sprayed with 3.5% Offshoot-O. A 4.5% Offshoot-O spray yielded 2.8 and 1.6 breaks with 'Chimes' and 'Kingfisher', respectively. Ethrel sprays seemed to have some influence on the number of breaks produced. Combined with Offshoot-O, Ethrel increased the number of breaks per shoot. The small increase in breaks, cost of materials and initial plant damage would probably rule out commercial use of the Ethrel-Offshoot-O sprays. Publications: Sanderson, K. C. 1969. Growth Retardants for Florist Crops A to Z. Florist Rev., Vol. 145, No. 3757. Annual Progress Reports available from authors. 4. Weed Control Studies by Kenneth C. Sanderson Department of Horticulture Nature of Work An experiment was designed to study the uses of herbicide mulches on liner production. Processed garbage, sawdust, and no mulch were compared. Dichlobenil ('Casoron') 4-G was incorporated into the mulches at the rate of 114 g and 57 g per cu ft when applied as a 1 in.and 2 in.mulch, respectively. Incorporation was done in a cement mixer in 1968 and by raking in broadcast dichlobenil in 1969. Other treatments included no mulch, no mulch with 114 g dichlobenil per 125 sq ft, and 1 in. and 2 in. mulches. Potted liners of Buxus harlandi, Rhodo- dendron obtusum jjpor cum 'Rose Banner', Juniperus chinensis 'Pfitzer', Viburnum burkwoodi, Ilex cornuta 'Matthew Yates', Juniperus conferta, and Thu r da- lie were mulched immediately after planting in July, 1968. Results Herbicide mulches were more effective in controlling weeds than other treat- ments. Combinations of 2 in. of sawdust and dichlobenil gave the best weed con- trol. Check plots which received no mulch or no herbicide were completely cover- ed with weeds three to four months after treatments were applied in 1968. Saw- dust without a herbicide was quite effective in controlling weeds when applied to a 2 in. depth. Plant death was higher with herbicide mulches (19%) than non- herbicide (13%); however, 1 in. sawdust-dichlobenil mulch had the least plant loss (2.9%). Processed garbage mulches had a high plant loss. Plant height and spread was greatest in plants mulched with the 2 in. sawdust-dichlobenil combi- nation. Herbicide mulches offer nurserymen and landscapers an effective weed control method. Not all plant species will tolerate dichlobenil. Publications: Sanderson, K. C. and Wo. C. Martin, Jr. 1969. Processed GarbageaUseful Mulch for Ornamental Plants. 1969. Highlights off Agric. Res.., Vol. 16, No. 3. Auburn-University, Alabama Agric. Expo Sta. Sanderson, K. Co 1970. Herbicide Mulches- A New Method of Weed Control. Highlights of Agric. Res., Auburn University, Alabama Agric. Exp. Stao