Wisterias can be propagated by various means for the hobby gardener.
Commercially, most Wisteria are propagated by grafting the chosen variety of cultivar, onto a seedling rootstock of the wild Wisteria - normally Wisteria sinensis.
However, for the amateur gardener, Wisteria are best propagated either from cuttings or layering.
They can also be grown from seed but with some variable results, and a long time before flower for some seed-raised Wisterias.
Softwood cuttings from Wisterias are taken from the plant at any time during Spring and Summer. Early Autumn is also a possibility, but will less successful results.
The cuttings are best taken from the base of a new side shoot (basal cuttings) with about 4-6in of growth above the base. Cut off the very top of the sideshoot which will be very soft and liable to wilt. You will then be left with a softwood cutting of no more than 4in long, but with at least one pair of leaves.
Treat the base of the cutting with hormone rooting powder or gel. Insert the cutting into a potting mix - into which sand or vermiculite has been added - 50/50 mix. Water the cutting well into the compost. Spray or dip the whole cutting with general fungicide. If inserting into a single 3-4in pot, then enclose the whole pot in a clear polythene bag and secure so that air-tight. Place in a sheltered place outside, in a coldframe, or in unheated greenhouse. Keep away from direct hot sunshine, but with plenty of natural light.
The cuttings should root within 6 - 8 weeks. During the 'waiting' time, inspect the cutting through the clear bag, and water when required. Maybe once weekly. Do NOT let it dry out. Once rooting has occurred - which will coincide with new growth on the cutting - just cut a slice out of the bag to allow gradual acclimatisation out of the very humid home that it has had for the last few months.
Keep the cutting in a sheltered place until well established, then nurse through the winter - out of drying winds and hard freezing of the pot and compost.. It will lose its leaves in the autumn.
Wisterias are quite easy to propagate from hardwood cuttings. The main advantage being that as the hardwood cutting of the Wisteria is leafless, there will be no wilting or desiccation of the foliage or stem.
The hardwood cutting is normally taken in either late autumn or early winter. Simply cut the mature vines into sections about 10in long. The individual cuttings should be cut at the bottom immediately below a leaf joint (node), with the top cut being around half inch above a leaf joint. The prepared cutting should now be around 6in long. It will be from wood produced in the previous summer, and not older wood. Treat base of cutting with hormone rooting powder or gel.
The cuttings can be bundled together, and then buried in a bed of light soil or peat bed outdoors until the spring. They can either be inserted upside down (The old way) or the right way up, or even lying horizontally. If the latter, then make sure that there is around 3in of soil/peat over the top.
In the spring, remove the cuttings and plant individually in a prepared bed, or in a deep pot. A deep pot is best to avoid any root disturbance when planting into final position. The top of the cutting (around 2in) with the leaf bud should be just above soil level. Rooting will probably take place in around 4 - 6 weeks and will coincide with the new shoots appearing at the tip of the cutting.
Wisterias can also be propagated either from air layering or soil layering.
Air layering or aerial layering is an easy way of growing an extra Wisteria. It is best carried out in early to mid summer.
Choose a new but established wisteria vine growth - around pencil thickness - and slice up through the stem at the bottom of a leaf joint (node). Make the cut so that it does not weaken the stem too much. Keep the slice open by inserting a matchstick or similar, and then surround the whole cut section with either peat or sphagnum moss enclosed in a polythene 'sleeve' secured at top and bottom with elastic bands, waterproof tape or twine.
The layered section should show roots in 5-6 months. When dormant, the rooted section can be taken off the main plant by cutting stem off from below the rooted section and either grown on in pot, or planted in flowering position.