Snip 15-20cm from the top of a vigorous shoot using sharp, clean secateurs.
Strip the lower leaves, then dip the cut end into root-promoting hormone gel or powder.
Fill a small pot with seed-raising or sieved potting mix. Insert the cutting to just below the leaves. Firm in.
Gently water and put in a warm, bright spot. Keep moist and, when roots form in about six weeks, carefully transplant into the garden or a larger pot.