This plant propagation method uses girdling

The correct option is layering.

Step-by-Step Explanation:

1. Understanding the terms:
- Girdling (or ring-barking) is the process of completely removing a strip of bark, including the cork cambium, phloem, and cambium, in a ring around a woody stem or branch.
- Plant propagation refers to the process of growing new plants from a variety of sources: seeds, cuttings, and other plant parts.

2. How layering works:
- Layering is a vegetative propagation method where a stem is encouraged to develop roots while still attached to the parent plant.
- In air layering (a common type of layering), girdling is performed on the target branch. Removing the ring of phloem prevents the downward flow of photosynthesized food (sugars and nutrients) and rooting hormones (auxins) past the girdled zone. This causes these essential substances to accumulate just above the cut.
- When moisture and a rooting medium (such as damp sphagnum moss) are wrapped around this girdled area, it stimulates rapid root development at the site of accumulation.

3. Comparing with other options:
- Cuttings: Stems are completely severed from the parent plant before roots are induced; girdling is not a standard part of this process.
- Grafting: This involves joining tissues from two different plants (the scion and the rootstock) so they grow together as a single plant, which does not rely on girdling to induce rooting.

Therefore, layering is the propagation method that specifically utilizes girdling to stimulate root formation.