22/Tree Planters’ Notes

ROOTING OF ALNUS RUBRA Philip A. Monaco, Te May Ching, and Kim 1 K. Ching CUTTINGS Department of Forest Science, Department of Crop Science, Department of Forest Science; Oregon State University, Corvallis

The growing interest in using dict. Third, individual variation of 2N sodium hydroxide mixed nitrogen-fixing plants in forest may mask phenotypic expression. with 100 percent ethanol and management to increase wood These disadvantages of propaga- diluted to the final concentration production for timber, fiber, and tion by seed can be overcome with distilled water (pH adjusted energy has prompted us to study through vegetative cloning. to 6.0). The final ethanol concen- the feasibility of cloning superior Unlike seeds, cuttings are always tration was 2 percent. The fungi- selections of alnus rubra Bong. available for producing plants of cide benomyl was prepared by (red alder). This plant is a moder- a known selection with minimum diluting a 50 percent commercial ately fast growing and widely dis- variability among individuals. preparation to 10 percent by the tributed nitrogen-fixing hard- The only rooting trial of A. addition of talc powder (1). wood tree in the Pacific rubra found in the literature was Following chemical treatment, Northwest and ,stay be a useful by Zach (5) who, using plant the cuttings were set to a depth silvicultural tool for maximizing hormones, reported a rooting of 2-3 cm in horticultural-grade yield in our forests. success of 1.3 percent. To estab- perlite, vermiculite and Lite-gro2 The advantages of establishing lish a more successful rooting (2:1 by volume) or perlite and clonal lines for agricultural plants methodology, we initiated our vermiculite (2:1 by volume). Plas - has long been recognized. Some own investigations: reported in tic 15x15 cm pots were used as of our most favored fruit trees this paper is the most successful containers, with 9 cuttings per have been maintained for over a rooting method tested. pot. century through vegetative prop- Rooting trials were conducted agation of specific genotypes (2). Materials and Methods under the following environ- Recently, the use of vegetative mental conditions: propagules in forestry has been Cuttings 15 cm in length and 5 investigated and recommended cm or less in diameter were col- Condition Temperature Humidity for the production of superior lected from greenhouse grown No. (day/night) Control genotypes (3, 4). seedlings (ca. 2 years old). All but 1 22°/16° C Overhead 3 Plants can be produced with lit- the top three leaves were greenhouse mist tle difficulty from seeds collected removed from the cutting to with 25° C bottom heat from genetically superior field- reduce transpiration. If the 11 25°/22° C Poly bags4 selected trees. However, for sev- remaining leaves were large, two growth eral reasons this method is not of them were crosscut in half to chamber always desirable. First, a seed further reduce water loss. The crop may not be available yearly basal ends of the cuttings were In condition I, a photoperiod from the selected tree. Second, dipped for 10 seconds in hor- was maintained by natural day the genetic expression of open- mone or a 2 percent ethanol solu- pollinated seed is difficult to pre- tion and dusted with 10 percent 2 benomyl. Lite-gro available from J. M. McConkey & Co. Inc., Box 309, Sumner, WA 98390. Freshly prepared indole-3- 1 3Pots were placed on a bottom heated Technical paper, Oregon Agricultural butyric acid (IBA) solutions of Exp. Station. This research was supported (25° C) bench with an intermittent over- different concentrations were by the Science and Education Administra- head mist of a 5-second timed spray every tion of the USDA under Grant No. 5901- used as the hormone. These solu- 12 minutes. 4 0410-8-0089 from the competitive Research tions were prepared by first dis- Pots were covered individually with clear Grants Office. solving the IBA in a small volume polyethylene bags vented for air circulation. Summer 1980/23

length (March-June) and sup- Table 1.—Effect of environmental and hormonal treatments on rooting plemented with 16 hours of fluo- percentages and number of cuttings with fewer or greater than 10 roots 1 rescent lights (ca. 4,400 lux). Con- dition II utilized only fluorescent Number of cuttings and incandescent lights (ca. 5,000 with: lux) for the 16 hour photoperiod. Treatment >10 roots <10 roots Rooting percentage

Results and Discussion Condition No. I 2 percent ethanol 0 5 44 Greenwood cuttings from A. 10 percent benomyl 0 4 56 rubra are readily rooted when 4,000 ppm IBA2 3 4 78 treated with high concentrations 4,000 ppm IBA, 10 percent benomyl 12 2 78 of IBA and set in a warm, humid 8,000 ppm IBA 8 4 71 environment. Rooting percent - 8,000 ppm IBA, 10 percent benomyl 14 4 82 ages of greenwood cuttings 10,000 ppm IBA, 10 percent benomyl 7 2 50 treated with 4,000-8,000 ppm IBA Condition No. II and 10 percent benomyl were greater than 50 percent 6 weeks 2 percent ethanol 0 0 0 10 percent benomyl 0 1 13 after treatment. Rooting percent- 4,000 ppm IBA 5 2 78 ages were similar using 4,000 or 4,000 ppm IBA, 10 percent benomyl 4 5 100 8,000 ppm IBA (table 1) except in 8,000 ppm IBA 7 0 78 one trial (table 2), where the 4,000 8,000 ppm IBA, 10 percent benomyl 7 0 100 ppm treatment rooted 46 percent 1 less than the 8,000 ppm dip. Greenwood cuttings with leaves set in perlite:vermiculite:Lite-Gro (2:1:1 by volume) However, cuttings treated with from 1- to 2-year-old greenhouse grown seedlings for 6 weeks. Condition I: 22°/16° C 8,000 ppm IBA produced more (day/night) with 25° C bottom heat and overhead mist. Condition II: 25°/22° C growth chamber. roots per cutting than those 24,000 ppm IBA equals approximately 20 mMolar concentration. treated with the 4,000 ppm solu- tion. In one trial rooting success increased 46 percent and number of roots per cutting 17 percent by treatment with 8,000 ppm IBA Table 2. —Effect of environmental and hormonal treatments on rooting instead of the 4,000 ppm concen- percentages and mean number of roots per cutting, condition No. II 1 tration. Treatment with 8,000 ppm IBA produced more well- Mean number branched roots than those cut- Treatment roots/cutting Rooting percent tings treated with 4,000 ppm (fig. 1). The 10,000 ppm IBA treatment 4,000 ppm IBA 8.5 ±9.4 44 had an inhibiting effect on root- 4,000 ppm IBA, 10 percent benomyl 15.75±9.6 51 ing in greenwood cuttings (table 1). 8,000 ppm IBA, 10 percent benomyl 19.0 ±9.2 95 Benomyl is considered benefi- 1Greenwood cuttings with leaves set in perlite:vermiculite (2:1 by volume) from 1- to 2- cial to cuttings because it inhibits year-old greenhouse grown seedlings for 6 weeks. Condition II: 25/22° C (day/night) fungal infection, thereby reduc- growth chamber.

24/Tree Planters’ Notes

I). Further studies must be con- ducted to resolve the effect of environment on rooting A. rubra cuttings. In summary, A. rubra can be vegetatively propagated by col- lecting greenwood cuttings from 1- to 3-year-old plants. Rooting is benefited by dipping the cuttings for 10 seconds in a 8,000 ppm IBA solution, dusting with 10 percent benomyl and setting in a well aerated planting mix. Cuttings rooted in 6 weeks when placed in a warm environment (22°-25° C day and 16°-22° C night) with high relative humidity and a 16 hour photoperiod.

Literature Cited 1. Brix, H., and H. Barker 1973. Rooting Studies of Douglas-fir Cuttings. Canadian Forestry Service.

Pacific Forest Research Center, Vic- toria, B.C. Infor. Report No. BC-X87 44 pp. 2. Hartman, H. T. and D. E. Kester 1975. Plant Propagation Principles and Practices. Third edition.

Prentice-Hall Inc. N.J. 662 pp. 3. Libby, W. J. 1974. The use of Vegetative Propa- Figure 1.—Rooting response after 6 weeks to different concentrations of gules in Forest Genetics and Tree IBA. Cuttings were dipped for 10 seconds in the IBA solutions and Improvement. N.Z. J. For. Sci. 4(2):440-447. dusted with 10 percent benomyl. (A), (C): 4,000 ppm IBA; (B), (D): 8,000 4. Lindgren, D. ppm IBA. 1977. Possible Advantages and Risks Connected With Vegetative Propa- ing mortality. In our studies, root- Rooting response to the envi - gation for Reforestation. pp. 9-16 ing percentages were generally ronmental conditions tested was In Vegetative Propagation of Forest Trees—Physiology and Practice. higher when we used a 10- variable. The cuttings responded Stockholm, Sweden. percent benomyl treatment. to the environments differently 5. Zach, L. W. Rooting success using benomyl depending on the concentration 1941. The Effect of the Synthetic Plant increased 21 percent and 13 per- of IBA. Using no IBA rooting was Hormones in the Propagation of cent in comparison to the ethanol best under the warm overhead Forest Trees. M.S. Thesis. Oregon State Agricultural College, Corvallis, control. mist environment (condition No. Oreg. 99 pp.