by Sammy Stein

Created on: April 30, 2009

Plant propagation is by two main ways - sexual or asexual. Sexual propagation is when a plant, either naturally or with thehelp of a plant breeder, transfers pollen from the male parts (anther) to the female parts (stigma) if a flower. Self pollinating plants can do this by transferring pollen to another flower on the same plant or even the same flower and those which cross pollinate do this,by using a vector like an inscet to take pollen from a flower on one plant to another flower on another plant of the same species.

However, plants can be propagated by asexual methods and this occurs in nature as well as being conducted by breeders and gardeners. Asexual propagation is useful because each offspring will be genetically identical to its parent plant. This means, if you get a variation of say flower colour or form, using asexual propagation, you can reproduce this to create a new variety.

The most common way of propagating plants like this is to take cuttings. Cuttings are piece of plant tissue taken when cells are rapidly dividing. The cutting process stimulates hormones called auxins to be concentrated in the area nearest the cut and new roots will eventually form. Cuttings are taken during rapid growth (softwood cuttings), after flowering (semi- hardwood cuttings) or at the beginning of the dormant season (hardwood cuttings) and different methods suit particular plants.

In nature, plants self-propagate asexually bt various means. They may put out side shoots underground (stolons or rhizomes) which will give rise to a new plant. They may layer, which is when a stem rubs against the ground (like with a blackberry bush), growth hormones concentrate at the site of injury and eventually new rots from and the old stem withers. A new plant then grows. Gardeners can do this themselves by cutting a main stem of the bush, filling it with moss, sealing it and waiting. Eventually new roots grow from the cut and you can remove this part of the stem from the main plant and plant it.

Many bulbs make new bulblets each year. In nature, these would eventually separate to become new plants but the plant propagator will lift the bulbs, separate the bulblets and plant each one separately to create new plants.

You can also divide clump forming perennial plants to propagate them. This involves the lifting of the root bundle and dividing it by gently prising it apart with a fork. Some root masses will divide into three or four small masses, each of which will create a new plant. Similarly, tubers (underground storage stems) can be cut into several sections, each with an 'eye' or bud and planted separately. Each one will eventually form a new plant.

You can even use leaves, single stems or roots to propagate plants. It is really just enhancing the processes which nature has devised for plants to propagate themselves and many of the processes have evolved to ensure that even if a pollinator is not around when a plant flowers, it can still spread by asexual propagation. Though it does not get the genetic diversity it needs, the plant increases and the gardener or plant breeder knows the commercial value of asexual propagation to because plants propagated this way do not breed true from seed - so the gardener needs to come back to the supplier if they want the same variety.

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