A how-to guide to getting an exact copy of the parent plant.

Vegetative propagation
Unlike seeds, plants reproduced vegetatively are an exact copy of the parent plant. This can be done by division (if the plants already have roots) and layering (inducing new roots to grow). A couple of other ways - taking a cutting and grafting (joining a plant with roots to one without) - have their own article in this series.

Division
Division (shown above) is probably the simplest means of propagating - a plant multiplies itself into a clump and you simply lift it from the ground, separate it into several sections and replant each one. Cut the clump apart with secateurs or a sharp blade. The best propagations are almost always the young, strong growths from the outside of the clump that come away fairly easily. Division is most appropriate with perennials and bulbs, but some thicket-forming shrubs can be divided too, or you can detach rooted suckers.

Layering
Many trailing or running plants layer themselves, forming roots where their runners touch the ground. These rooted sections can be severed from the parent, dug up and replanted.

Most shrubs with branches that can be bent low enough to touch the ground can also be layered. Bend a suitable branch down, make a nick by cutting into but not through the lowest point, bury it, and when it has made roots in a few weeks or months, detach the new plant and transplant it. You need to hold the branch still, say with a brick on top of the buried section. Layering is good with any plant that will also grow from cuttings.

The plant on the right is being layered. First a stake was put in to hold the plant and a shoot was stripped of leaves and nicked with a sharp knife where the new roots were to grow. Then the stem was buried. New shoots are now forming.

Air-layering
If you can't bend a branch down to the ground you can take the soil to the plant in what is called air-layering or marcottage. Select the point where you want roots to grow, make a nick in the stem there and pack some moist sphagnum moss or peatmoss around it, tying it in place with a piece of plastic bag. When you see roots through the plastic, cut the branch off and plant it (taking the plastic away, of course). Air-layering can be done to almost any shrub that will strike roots from a layering or cutting. Make sure that the moss doesn't dry out by sealing the plastic well.

Source:Gardening: A Commonsense Guide (Murdoch Books)