Rooting hormones improve uniformity among vegetative cuttings
Rooting compounds aid in rooting of moderate to difficult-to-root species, accelerate root initiation, improve rooting uniformity, increase the number of roots produced and reduce shrink and rooting time.
Rooting hormones are a great addition to any propagator’s toolkit. Rooting compounds, being liquid or powders, when applied properly aid in rooting of moderate to difficult-to-root species, accelerate root initiation, improve rooting uniformity, increase the number of roots produced and ultimately reduce shrink and rooting time. Of course, when rooting hormones and other cultural practices are combined with optimal environmental conditions, results are high-quality, well rooted liners.
Rooting compounds are essential for rooting difficult-to-root annual and perennial bedding plant species and sometimes used for those that may be moderately difficult. Tables 1 and 2 provide an extensive list of annual and perennial bedding plant species that have a high (difficult-to-root), moderate or low benefit (no hormone) to rooting hormone applications prior to sticking or during propagation. Annual and perennial bedding plant species that are listed as having a low benefit typically root without any hormone application.
Rooting hormones come in various formulations and contain different ingredients (Table 3) and can most often be applied in one of three ways: quick-dips or dipping the basal or cut end of the cutting into the rooting hormone prior to sticking; stem base sprays; or post stick foliar sprays. Application methods most commonly observed among Michigan greenhouse growers is the quick-dips and post stick foliar sprays.
|Table 1. List of annual bedding plant species with low, moderate or high beneficial response from a rooting hormone application in propagation.|
|Low benefit||Moderate benefit||High benefit|
|Impatiens – Double||Bacopa||Lobularia||Cineraria|
|Impatiens – New Guinea||Begonia – Hiemalis||Lophospermum||Crossandra|
|Ipomoea||Begonia – Reiger||Nemesia||Dahlia|
|Petchoa||Begonia – Rex||Oternaria||Dracaena|
|Table 2. List of perennial species with low, moderate or high beneficial response from a rooting hormone application in propagation.|
|Low benefit||Moderate benefit||High benefit|
|Table 3. Examples of various formulation and ingredients in rooting compounds used for annuals and perennial propagation (powders, liquids, tablets, and water-soluble salts).|
|Chryzopon||Powder (talc)||0.1% to 8% IBA|
|C-mone||Liquid (isopropyl alcohol)||1% and 2% IBA|
|C-mone K||Liquid (isopropyl alcohol)||1% K-IBA|
|C-mone K+||Liquid (isopropyl alcohol)||1% K-IBA + 0.5% NAA|
|Dip ‘n Grow||Liquid (alcohol)||1% IBA + 0.5% NAA + boron|
|Hormex||Powder (talc)||Rooting Powder—0.1% to 4% IBA|
|Hormex||Liquid||Hormex Concentrate—0.013% IBA + 0.24% NAA + vitamin B-1|
|Hormodin||Powder (talc)||0.1%, 0.3% and 0.8% IBA|
|Hormo-Root||Powder (talc)||0.1% to 4.5% IBA|
|Hortus||Water-soluble salts||20% IBA|
|IBA Water Soluble Salts||Liquid||20% IBA|
|Rhizopon||Powder and water-soluble tablet form||0.1%, 0.3% and 0.8% IBA|
|Stim-Root||Powder (talc)||0.1% and 0.4% IBA|
|Woods Rooting Compound||Liquid (ethanol)||1.03% IBA + 0.56% NAA|
For quick-dips, the basal end of the cutting is dipped into a talc powder or solution containing an auxin-based hormone. When using powder rooting hormones, dip the basal end of the cutting into the talc powder (Photo 1). The cutting should not be wet as moisture will cause the powder to clump. Lightly tap the cutting to remove excess powder prior to insertion into the propagation substrate. In general, powder forms of rooting hormones are less effective than liquid auxin-based formulations applied at the same concentration.
Procedures for liquid auxin-based rooting hormones applied as a cutting dip is similar to those indicated for powders. In general, cuttings are dipped in a water- or alcohol-based solution containing 500 to 1,000 parts per million indole-3-butyric acid, or IBA (Photo 2). Application rates are species-specific and sometimes cultivar-specific. Read and follow the label rate for each species.
To apply the solution, submerge 0.25 to 0.75 inches of the cutting base into the solution for no more than 1 to 5 seconds. This is referred to as quick-dips. After dipping, keep the cutting vertical (cutting end down) thereby avoiding excess solution running down to the apical meristem (tip). If alcohol-based rooting hormone solutions touch the apical meristem, twisting of leaves (epinasty) can occur.
Quick-dips are easy and often result in uniform rooting, though they can be labor intensive, dehydrate cuttings and increase the risk of disease contamination. Therefore, refresh rooting hormone solutions daily and between species or batches of cuttings.
Post stick foliar sprays applications are simple and are becoming more popular among growers in Michigan and across the U.S. When applying the rooting hormone, for example K-IBA, spray the solution to the point of runoff. Spray applications are often applied within 24 hours after cuttings are stuck and placed in the propagation environment.
The rooting hormone concentration for post stick foliar spray applications are often lower than quick-dips and require less labor and chemical handling. The simplicity of this application method will allow growers to be more efficient and produce uniform rooted liners.
Prior to handling any chemical, always read the label or MSDS sheets for health hazards and personal protective equipment (PPE) requirements. When mixing rooting hormone for quick-dips and post stick foliar sprays, wear protective eyewear, gloves, long-sleeve shirts and close-toed shoes. When applying quick-dips to cuttings, Michigan State University Extension highly encourages wearing gloves.
If a species is not labelled, conduct an in-house trial with a low rate of rooting hormone, contact the manufacture of the rooting hormone or contact your greenhouse educator or outreach specialist.