What external factors affect the rooting of flower cuttings?

Many factors affect the rooting of cuttings, and fundamentally of course it comes down to differences in genetic characteristics. But based on general traits, it can still be considered from several aspects:

1. Substances necessary for rooting: Through extensive experimental analysis, rooting-inhibiting substances have been identified: it is generally believed that the cutting itself contains substances that hinder rooting, such as tannins, resins, organic acids, etc. These substances can weaken or block the action of plant growth hormones, and at the same time these substances remain on the cut surface, affecting water uptake by the cutting, thereby reducing rooting ability. Soaking the base of the cutting in alcohol or hot water can, to a certain extent, enhance the rooting effect.

2. Drought and rot of cuttings: Withering of cuttings seriously affects rooting and leads to rooting failure, and the main causes of withering are drought and rot. Drought is caused by excessive water loss in the cutting during transport or cutting processing, or after planting when the cutting bed is dry and evaporation is high, causing the rooting activity of the cutting to be severely damaged, or even causing it to die. Therefore, water conditions in the cutting bed must be managed well, the transpiration area should be reduced or shading measures should be taken to lower transpiration intensity and prevent withering, so as to ensure survival after rooting.

Rot is caused by infection of the cut at the base of the cutting by pathogenic bacteria. After rotting, the cutting dies because it cannot absorb water or because it loses metabolic capacity. Therefore, strengthening cut protection and disinfecting the cutting bed substrate are very effective for preventing rot and increasing the rooting survival rate. For cuttings that rot easily, choosing suitable cutting bed materials is very important; sterile soil containing no or little organic matter can prevent rot to a certain extent. For succulent plants that rot easily, such as cacti, before planting the cuttings they should be placed in a cool, dry place, and only after the cut has healed should they be inserted, which can achieve good results. Therefore, during rooting, attention should be paid to preventing withering caused by drought or rot, creating good cutting bed conditions and other environmental conditions, prompting the cuttings to root as early as possible, and shortening the dangerous period before rooting as much as possible.

3. Age and maturity of the cutting: Comparison shows that cuttings taken from branches of older trees are difficult to root, while those taken from young trees or vigorous shoots sprouting from the trunk root easily. For example, for olive, the rooting rate of cuttings from one-year-old young branches reaches 100 percent, while the rooting rate of cuttings from two-year-old branches drops to 50 percent, and cuttings from old branches more than three years old cannot root.

From the perspective of cutting maturity, one-year-old branches root more easily than branches with a higher degree of perennial lignification, and new shoots of the current year root more easily than one-year-old branches. For example, one-year-old branches of Bitao cannot root when used as cuttings, but in autumn, using semi-lignified branches of the current year as cuttings can achieve survival. The reason is that young branches have strong vitality and readily produce new root primordia and form adventitious roots; here the role of leaves and stems is also inseparable, because leaves not only produce nutrients, but the auxin they produce can also promote the formation of root primordia and the growth of adventitious roots.