by Heidi Lindberg

Using surfactants in vegetative cutting propagation

There are many factors that contribute to the success of propagating unrooted cuttings (URC) and callused cuttings (CC) including: time to stick, light intensity, misting frequency, humidity, root-zone heating, temperature, ethylene exposure, and the use of rooting hormones. Dr. Garrett Owen covers the moisture requirements in his recent article, “Moisture management during vegetative cutting propagation” on Michigan State University Extension’s floriculture website. Dr. Roberto Lopez and I published e-GRO Alert 5.6 “Increasing the Rooting Success of Challenging Vegetative Cutting Species” last season listing the priority of plant species for sticking in propagation. Last week Dr. Roberto Lopez published e-GRO Alert, “Avoid Cutting Losses by Prioritizing Sticking” which shows what happens to the quality of problematic species when those guidelines are not followed.

by Heidi Lindberg -

Another tool that some greenhouse growers use to increase the rooting success of their vegetative cuttings is the use of a surfactant. Some greenhouse growers swear by using surfactants in their mist solutions during vegetative cutting propagation in order to decrease the surface tension of the water allowing it to spread uniformly over the leaves (Figure 1). Without it, the water from frequent misting may bead up on the leaves (Figure 2). Misting is used to prevent desiccation, or further water loss from the leaves of the cutting and not to re-hydrate the cuttings. The cuttings will absorb water from the propagation substrate (oasis block, peat/perlite etc.) upon root emergence.

Figure 1. When using Capsil, a common greenhouse spreader -sticker, the water on poinsettia vegetable cuttings spreads out evenly over the leaves. Photo: Dr. Roberto Lopez.

Before delving into the research on using surfactants in greenhouse propagation, let’s clarify the definitions of terms that are often used interchangeably and may be confusing: adjuvants, surfactants, spreader-stickers, and wetting agents.
  • Adjuvants: The broad term that is used to describe any additional products used to increase the efficacy of pesticides (insecticides, fungicides, miticides, plant growth regulators, etc.)
  • Surfactants: Surfactants are a type of adjuvants that reduce the surface tension of water upon contact with the crop’s canopy. They effectively “spread -out” the water droplets to improve coverage.
  • Spreader-stickers: This term used to describe a surfactant, which spreads out the water droplets, with the addition to a compound that prevents the droplets from rolling off the leaves.
  • Wetting agents: This term is sometimes used incorrectly. Wetting agents are additives often amended to substrates to allow hydrophobic components such as peat moss to “re-wet” after they have dried down and prevent “channeling” down the side of the container wall. These compounds, liquid or powder -based, have different properties than surfactants and are not compounds that you can spray directly onto plants.

Figure 2. Beading of water on poinsettia cuttings without using an adjuvant. Photo: Dr. Roberto Lopez.

Check out the full e-GRO Alert here.

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