Many growers propagate unrooted cuttings, but propagation success varies among species, cultivars, and environmental conditions. Rooting hormones can be used to ensure and improve the rooting success of vegetative shoot-tip cuttings.
Many annual and herbaceous perennial bedding plants can successfully be propagated from unrooted shoot-tip cuttings. Growers must maintain a favorable propagation environment and implement cultural practices to promote root initiation and subsequent root growth and development. While many growers may be challenged with achieving an optimal propagation daily light integral of 8 to 12 mol·m–2 ·s–1 or maintaining desirable air and root-zone temperatures or vapor pressure deficit, most all growers can easily implement rooting hormones.
Rooting hormones are considered plant growth regulating chemicals because they stimulate a favorable response in plants – rooting. When applied properly, rooting hormones can accelerate root initiation, improve rooting uniformity, aid in rooting of moderate to difficult-to-root species, increase the number of roots produced per cutting, and ultimately reduce shrink and propagation time. Of course, when rooting hormones and other cultural practices are combined with optimal environmental conditions, the results are high-quality, well-rooted cuttings (liners).
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