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Advances using Indole-3-butyric Acid (IBA) dissolved in water for rooting cuttings, transplanting and grafting.
Hortus USA Corp.
PO Box 1956 Old Chelsea Station
New York, New York 10011-1717
International Plant Propagators' Society, Eastern Region, 42nd Annual Meeting, December 2, 1992
Since the 1930's the plant growth regulator Indole-3-butyric acid (IBA) has been used for rooting of plant cuttings and other growth processes. Thousands of articles have been written on it as the favorite single compound used to promote rooting. Uses for IBA other than rooting include promoting root regeneration when transplanting rooted plants and to improve grafting. Useful compounds containing IBA are solutions and powders. Solutions of IBA dissolved in water are useful for more purposes than any other compound.
KEY WORDS: IBA, IBA water soluble, Indole-3-butyric acid, plant growth regulator, Rhizopon, root regeneration, rooting plant cuttings, transplant rooted plants, grafting.
IBA DISSOLVED IN LIQUID CARRIER
Solutions of IBA are used for rooting of plant cuttings, transplanting of rooted plants, and to improve grafting. Concentrations used for rooting are from 10 ppm to 20000 ppm IBA. The method of use and concentration of IBA is determined by many variables including plant variety, time of year, propagation conditions, etc. Liquid sources of IBA are premixed concentrated liquids containing up to 1.03% IBA dissolved in organic solvents, up to 99.5% alcohol (EPA registrations as of 1992) and water soluble tablets containing 20.0% IBA which are made into solution by the grower. The only US registered IBA water soluble tablet is Rhizopon AA Water Soluble Tablets (Importer: Hortus USA Corp., PO Box 1956, New York NY 10113) (Blazich, 1988; Hartmann, 1990; Macdonald, 1986).
Methods using solutions containing IBA to root plant cuttings are Immersion, Total Immersion, Quick Dip, and Spray Drip Down ®. To promote root regeneration when transplanting rooted plants the method used is Immersion-Absorption. For improving grafting the method used is immersion of the scion.
IBA dissolved in water is more effective for rooting most plant species than IBA dissolved in alcohol, or other auxins, indoleacetic acid (IAA) or naphthalene acetic acid (NAA) (Blazich, 1988, Hitchcock and Zimmerman, 1939). Other than water soluble IBA are insoluble acid salts of IBA which are usually dissolved in high concentrations of alcohol. High concentration of alcohol may dehydrate, injure and be toxic to basal stems, scions, and other plant tissue (Blazich, 1988).
A working solution using IBA dissolved in high percentage alcohol has another serious disadvantage. When the alcohol rapidly evaporates the ppm concentration of the IBA increases. Increased ppm IBA concentration beyond the threshold of auxin tolerance will inhibit plant growth (Blazich, 1988).
IBA BLENDED IN POWDER CARRIER
Magnesium silicate (talc) blended with IBA is used to root cuttings by the Dry Dip method. The basal end of the cutting is dipped approximately 3/4" into the powder before planting in media. For rooting, benefit comes when a uniform amount of powder adheres to the cutting. If the powder is brushed off when the cuttings are stuck in the media or if a non-uniform amount of powder is applied there may be inconsistent results. For different plants and season the powder must be stocked in a wide range of IBA concentrations ranging from 0.1%-8.0%. IBA is also used to improve grafting when the powder is applied to the scion by direct application.
Methods and concentrations not cited as follows are from the "Rhizopon Stektabel" protocols (Rhizopon, 1992).
IBA USED FOR ROOTING OF CUTTINGS
IBA is applied to plant cuttings for rooting using powder (Rhizopon AA dry powders) or liquid carrier (Rhizopon AA Water Soluble Tablets). Different concentrations are used for different plant varieties, season, and other variables. Methods using IBA in solution are Immerse, Total Immerse, Quick Dip, and Spray Drip Down ®. It is difficult to relate concentration to promote rooting when comparing IBA blended in powders and liquids (Blazich, 1988; 1973; Bonaminoto, 1983; Bonaminoto and Blazich, 1983, Hitchcock and Zimmerman, 1939, 1936). Variation is due to the method of application, retention, and use of the IBA by the plant tissue.
IBA USED FOR ROOTING OF CUTTINGS BY IMMERSION
The IBA Immerse method is suited to hard to root plants. It is used to root prunus rootstocks, evergreen. deciduous shrubs. conifers. platanus acerifolia (London plane) (Macdonald. 1986. ill.: pg. 345-346). Immerse the basal ends of the cuttings approximately one inch in solution for 4-12 hours. For cuttings propagated under mist the treatment is a maximum of tour hours. The cuttings are planted immediately after treatment. For woody and herbaceous cuttings use 50-150 ppm IBA dissolved in water (using Rhizopon AA Water Soluble Tablets).
European growers have for over fifty years used the IBA Immerse method to root cuttings of prunus rootstocks including St. Julien (plum and other stone fruit, etc.). In the Autumn sixteen inch cuttings are taken from the parent plant. Basal ends of the cuttings are Immersed in 100 ppm IBA dissolved in water for 6-12 hours. Cuttings are then bundled in groups of 25. Bundles are wrapped in perforated transparent plastic sheeting. The wrapped packages are placed into crates which are piled to allow air circulation. The crates are left in cold storage at a temperature above freezing (33-35F) for the Winter. Ethylene generation is checked regularly as it could be toxic to the cuttings. During cold storage a callus ferrule forms around the lower end of the basal end. In the Spring the cuttings are planted in the open.
IBA USED FOR ROOTING OF CUTTINGS BY QUICK DIP
Many growers prefer the IBA Quick Dip Immersion of basal ends for rooting of cuttings. Uses are well documented (Hartmann, 1990). Quick Dip may have variable rooting since the cuttings are immersed a brief time at high concentration IBA; there may be inadequate absorption of the IBA. The basal ends of cuttings are immersed approximately one inch in solution for a few seconds. The cuttings are planted immediately after treating. Using Rhizopon AA Water Soluble Tablets: For herbaceous, tropical plants, house plants, roses use 150-500 ppm IBA dissolved in water. For chrysanthemum use 150-500 ppm IBA dissolved in water (concentration is dependant upon growing conditions). For softwood cuttings use 1000 ppm IBA. For hardwood cuttings use 2000 ppm IBA. For difficult to root hardwood cuttings use 5000 ppm IBA up to 20000 ppm IBA. 20000 ppm IBA with very fast dip time is used in rare cases for extremely difficult to root plants.
IBA USED FOR ROOTING OF CUTTINGS BY TOTAL IMMERSION
Total Immersion of the cutting produces high quality roots. Immerse the whole cutting in solution for a few seconds. Plant the cutting immediately. For herbaceous cuttings, plumbago, ivy, clematis, delphinium, lavender, ficus use 50-250 ppm IBA dissolved in water (using Rhizopon AA Water Soluble Tablets).
Shoot cuttings of berberis, cotoneaster, lavandula, prunus, pyracantha, and viburnum. Total Immersed in an IBA solution were shown to give better rooting than dipping the basal ends of the cuttings in IBA by Dry Dip. Cuttings were Immersed two minutes in 1000 ppm IBA dissolved in water. The Total Immersed cuttings produced increase in the fresh weight of the roots as compared to Dry Dip. (Van Brash, 1976).
IBA USED FOR ROOTING OF CUTTINGS BY SPRAY DRIP DOWN®
The Spray Dip Down method is cost effective since it uses minimum labor and low IBA concentration. Chrysanthemum growers in many parts of the world use this method exclusively. Cuttings are first planted in well spaced trays. The solution is sprayed on the leaves and stems until beads of liquid Drip Down into the media. Uniform symmetrical roots are produced. For chrysanthemum, begonia, dieffenbachia, heath, hibiscus use 50-250 ppm IBA dissolved in water (using Rhizopon AA Water Soluble Tablets).
TWO METHODS TO ROOT CHRYSANTHEMUM CUTTINGS
For two full years (1989-91) the research department at Lyraflor, de Lier, Holland with the Rhizopon researchers did large production tests to root chrysanthemums and pot chrysanthemums. Two methods produced similar results; roots of cuttings were high quality and symmetrical. (1) Spray Drip Down ® using 5-150 ppm IBA dissolved in water (Rhizopon-AA Water Soluble Tablets at 1-3 tablets per liter). (2) Quick Dip immerse of the basal end of the cutting for two seconds 150-400 ppm IBA dissolved in water (Rhizopon-AA Water Soluble Tablets at 3-8 tablets per liter) (Eigenraam, 1990).
THREE METHODS TO ROOT ROSE CUTTINGS AND STENTING ROSES
Research by the Rhizopon Research Center' Hazerswoude. Holland concluded that rose cuttings produced quality roots by each of three methods. (1) Dry Dip at 0.25C%c-0.6% IBA. (2) Quick Dip Immerse at 250-500 ppm IBA dissolved in water (Rhizopon-AA Water Soluble Tablets at 5-10 tablets per liter). (3) For potted roses, Spray Drip Down ® at 50-100 ppm IBA (Rhizopon AA Water Soluble Tablets at 1-2 tablets per liter) (Eigenraam. 1990).
Current rooting research projects supported by Hortus USA and Rhizopon include rooting of acer rubrum (scarlet maple) and prunus (apricot) using IBA dissolved in water compared with Dry Dip, and rooting of malus (apple rootstocks) using IBA dissolved in alcohol compared with IBA dissolved in water.
IBA USED FOR ROOT REGENERATION WHEN TRANSPLANTING ROOTED PLANTS
Research on woody plants, quercus coccinea (scarlet oak) and nyssa sylvatica (black gum) seedlings, IBA solutions promoted increased number of regenerated roots rather than elongation. Optimum concentrations (tested on black walnut, tulip tree, and scarlet oak) for bare root Immersion-Absorption for five minutes was 1000-3000 ppm IBA. Three thousand ppm IBA and immersion longer than five minutes inhibited root regeneration and shoot development (Struve, 1984).
IBA USED FOR ROOT REGENERATION WHEN TRANSPLANTING ROSES
Rose crops start with transplanting dormant bushes. Survival of transplants requires rapid root regeneration. Treatment with a IBA solutions speed new root initiation and increases root elongation rate. Survival is improved and there is earlier and higher flower yield. IBA solutions applied to root segments of Rosa multiflora 'Kanagawa' increased numbers of regenerated roots and root length. Best results were achieved then the roots were immersed in 1000 ppm IBA dissolved in water for five minutes. 'Montrea' on rootstock Rosa canine 'Inermis' had the most effective concentration at 500 ppm IBA dissolved in water. Application of NAA and IAA were not as effective (Fuchs and Poll 1986: Fuchs. 1986).
IBA INFLUENCE ON FLOWER YIELD WHEN TRANSPLANTING ROOTED ROSE BUSHES
Traditionally American rose growers allow one to two years of growth before transplanting rose bushes. Without special treatment a young rose transplant uses its energy to rebuild a root system instead of entire plant growth. Without a strong root system the plant has reduced ability to feed and receive water therefore it is subject to stress and possible mortality.
Dutch rose growers have for almost fifty years transplanted half year old rose bushes. To improve root regeneration and increased first year flower yield when transplanting bare root rose bushes the roots are immersed in a solution containing Rhizopon-AA Water Soluble Tablets, active ingredient IBA, dissolved in water. The roots are not cut back except damaged or broken roots. Living roots contain stored carbohydrates required by the plant for regrowth. The bare roots are immersed ten minutes in 150 ppm IBA dissolved in water or five minutes in 250 ppm IBA dissolved in water. Water is used to make solutions to eliminate toxic effects of strong solvents.
After treatment the rose bushes are planted immediately. At planting time the soil temperature is kept above 60F and air temperature above 65F with relative humidity at 80%. Warm soil temperature is a cofactor in utilization of IBA (Fuchs and Poll 19X6: Fuchs, 1986).
The Hortus USA Research Center used IBA Immersion-Absorption when transplanting Simplicity (TM) shrub roses (Jackson and Perkins, Medford, OR). The treated plants had consistently higher flower yield during the growing season, up to 60%, over the control plants. Before planting the bare roots were immersed ten minutes in 150 ppm IBA dissolved in water. The IBA source was Rhizopon AA Water Soluble Tablets. After treatment the plants were planted in the field immediately. Leaf and stem growth and start of flower buds was similar on both test and control plants. Results suggest first stage growth of leaf flush came from stored carbohydrates; second stage growth of the flowers was influenced by the IBA (Rhizopon Researcher, 1992).
Current transplanting research projects supported by Hortus USA and Rhizopon. Projects include the effect of IBA when transplanting Ribes grossularia (gooseberry), transplanting prunus and Betula in leaf from tissue culture, and applications of low concentration IBA during watering of difficult to transplant paw seedlings.
IBA USED FOR GRAFTING
Propagation by grafting of ornamental conifers is often unpredictable and variable. IBA has been used to stimulate cell division at the graft site. Grafts of Picea pungens 'Hoops' (blue spruce) on Picea abies rootstock were improved: immerse the scion bases for three minutes in 200 ppm IBA before joining Treated grafts were consistently improved by 13% over the controls (Beeson, 1990).
Scion wood of carya illinoinensis (var. 'Desirable' pecan) were successfully grafted onto the lateral roots of 'Van Deman' pecan seedling root stock by Dry Dip the scion in 1% and 2% IBA in talc base. Shoot survival for IBA treated grafts was 20% higher than the controls (Yates, 1992). Research is necessary to determine if liquid Immersion of the scion will have similar success.
Current layering and grafting research projects supported by Hortus USA and Rhizopon include: use of IBA dissolved in water for air layering corylus (hazel), grafting corylus, pyrus, malus, prunus and other stone fruit, and grafting diospyros virginiana.
TESTING IS ESSENTIAL
The condition of the plant material and the resultant rooting potency, varies from season to season. Plants must be checked regularly and adjustments made to the IBA concentration, method of application, other growing agents, timing, and propagation environment. Follow-up adjustments are part of the normal growing operation.
Rooting variables should be kept to simple terms. Tests combining IBA with other auxins (NAA, IAA), plant growth regulators, fungicides, herbicides, insecticides or fertilizers are difficult to evaluate. Each compound may be cofactor. IBA as a single component growth regulator is predictable since it has well-established efficacy. Results may also vary due to stock clonal variation.
IBA: A REGISTERED PLANT GROWTH REGULATOR
US Growers are aware that they must only use EPA registered plant growth regulators to meet OSHA and state requirements. These requirements help protect their business, their stock, and the health of their workers. The auxins, of which IBA is included, have undergone extensive scrutiny for efficacy, toxicology and phyto toxicology. The EPA carefully stipulates the label including precautionary statements to protect the user. Unregulated so called 'vitamin hormones' with unknown efficacy and safety must be required to be tested under EPA guidelines using Good Laboratory Practice (GLP). The grower and the worker must be protected.
IBA dissolved in water is a useful growth regulator for the plant grower and propagator. It is used for rooting of plant cuttings by Dry Dip, Total Immerse. Immerse, Spray Drip Down ® and Quick Dip methods. Root regeneration is promoted when transplanting rooted plants using IBA by Immersion Absorption; it promotes plant growth and higher flower yield. IBA improves graft takes of difficult to graft plants. Future development will come from trying successful methods using IBA on a wide range of plants, new application methods and carriers.
REFERENCES AND ADDITIONAL READING
Articles on Plant Propagation
Beeson Jr., R.C., Proebsting, W.M. 1990. Propagation tips for blue spruce. American Nurseryman Magazine. July 15 1990:86-90.
Blazich, F.O. 1988. Chemicals and formulations used to promote adventitious rooting, pg:l32-147. In: Davis. T.D., Haissig, B.E., Sankhla, N., Adventitious Root Formation in Cuttings, Advances in Plant Sciences Series, Vol. 2. Dioscorides Press, Portland, OR.
Bonaminoto. V.P. 1983. Comparison of IBA Quick Dips with talc for rooting cuttings. Proceeding of the International Plant Propagators Society. 33:565-568.
Bonaminoto, V.P., Blazich, F.O. 1983. Response of Fraser's photinia stem cuttings to selected rooting compounds. Journal of Environmental Horticulture. I :9- 11.
Eigenraam, C.A., Grootschoten, M. 1990. Rhizopost. Rhizopon B.V., Hazerswoude, Holland.
Fuchs, H.W.M. 1986. Root regeneration of rose plants as influenced by applied auxins, Acta Horticulturae, 189:101-107.
Fuchs, H.W.M., Van Pol, P. 1986. Harvesting, pruning and root reactions of roses. Acta Horticulturae,189: 109-115.
Hartmann, H.T., Kester, D.E., Davies, F.T. 1990. Plant Propagation Principles and Practices (5th edition). Prentice Hall, Englewood Cliffs, NJ.
Heung, S.L.R., McGuire, J.J. 1973. Effect of formulation on uptake of 3-indoleacetic acid in cuttings. Proceeding of the International Plant Propagators Society. 23:296-304.
Hitchcock, A.E., Zimmerman, P.W. 1936. Effect of growth substances on the rooting response of cuttings. Contr. Boyce Thompson Institute. 8:63-79.
Hitchcock, A.E., Zimmerman, P.W. 1939. Comparative activity of root inducing substances and methods for treating cuttings. Contr. Boyce Thompson Institute. 10:461-480.
Macdonald, B. 1986. Practical Plant Propagation for Nursery Growers (Volume 1). Timber Press, Portland, OR.
Rhizopon Researcher. 1992. Transplanting rose bushes using Rhizopon AA Water Soluble Tablets, Hortus USA, New York, NY. 1:1(1-2).
Rhizopon Stektabel. 1992. Rhizopon B.V., Hazerswoude, Holland.
Struve, D.K., Moser, B.C. 1984. Auxin effects on root regeneration of scarlet oak seedlings. Journal of American Society of Horticultural Science. 109(1):91-95.
Van Bragh, J., Van Gelder, H., Pierik, R.L.M. 1976. Rooting of shoot cuttings of ornamental shrubs after immersion in auxin containing solutions. Scientia Horticulturae , 4(1976):91-94.
Yates, I.E., Sparks, D. 1992. Pecan cultivar conversion by grafting onto roots of 70 year old trees. HortScience. 27(7):803-807.
Make sure you store the solutions properly: storage
The advantage of Rhizopon AA Water Soluble Tablets and Hortus IBA Water Soluble Salts is briefly discussed:
NEW important presentation. How a major plant propagator improved plant propagation from cuttings using sequential foliar applications of Hortus IBA Water Soluble Salts rooting solutions
Foliar Application of Rooting Hormones