
Hi Helen,
You can take cuttings of wisteria but it is so important to make sure you take them from a plant that flowers reliably otherwise you may wait many years for flowers. If the plant is in a friends garden I suggest you propagate it by layering. To do this select a long shoot of current seasons growth. Kink the stem and peg it into a shallow hole in the earth near the parent plant. The end of the shoot is still attached to the parent plant at this stage. Leave this for about a year. When you return the shoot should have rooted where it was buried in the ground and you can cut it off from the parent plant, transplant it and grow it on.
I find layering more successful than cuttings but if you care to try I suggest you take hardwood cuttings in the early winter, once the parent plant has lost its leaves. The cuttings should be about 20cms (8") long and the portion of the shoot nearest the base of the plant will root better than the immature tip. Cut below a bud at the base and above a bud at the tip of the cutting. Dip the base in fresh hormone rooting proder and insert the "sticks" into deep pots sodd in a sheltered place. The cuttings may not root until late spring the following season so take care to keep them watered.