Posted: 14/06/2013 at 23:44
No personal experience with wisteria but ...
Cuttings of wisteria need to be taken from the softwood. This is wood that is still green and has not developed woody bark. The cutting should be about 3-6 inches long and have at least 2 sets of leaves on the cutting. Wisteria cuttings root best if taken in late spring or early summer. Once you have the cutting, remove any sets of leaves found on the lower half of the wisteria cutting. These will be the main points where new roots will develop. Trim the cutting so that the lowest node (where the leaves you just removed were) are 1/2 -1/4 inch from the bottom of the cutting.
The cuttings should be 4 to 6 inches long and you can take them either late in the winter ("hardwood" cuttings) or in early summer, after the flush of new growth has slowed ("semi-hardwood"). Rooting hormone powder speeds the formation of roots. You'll need almost greenhouse-like conditions of bright light and high humidity.
Well, that's nice and contradictory, isn't it?
I think in general it's an early summer job, so you get a growing piece as a cutting and the cutting gets all summer to sort itself out while it's sunny and is a plant ready to be put in the ground in spring.
What they say about plastic bags and greenhouse conditions is what described in the honeysuckle thread: http://www.gardenersworld.com/forum/plants/honeysuckle/4479.html
Use a large plant pot.
Put short canes around the sides of it.
Fill it with moist but not wet compost.
Get a bucket (or vase, mug, coffee jar or watering can) of water.
Cut off a short length of growing stem with a few pairs of leaves, and immediately put the cut end into the water so it doesn't dry out.
If it'll take you a while to get the cutting to the bucket, take a longer cutting and cut off the bottom few inches under the water. Cuttings dry out from the cut end upwards.
Remove the lower leaves from your cutting. I stripped the outer bark off the bottom inch too. It'll try to heal, and how it tries to heal depends on where it finds itself.
You can add hormone rooting powder or other goop at this point, but I didn't bother and it still worked.
Transfer the cutting from the bucket to the centre of the pot of compost.
In some cases, this could be enough. Winter-flowering honeysuckle stem 18" long rammed 12" deep in the soft soil behind the compost heap has become a small shrub. However, the greenhouse thing helps. Your cutting has no root system, but it does have leaves, putting it at risk of drying out. You can't remove all the leaves or it'll have no source of power and CO2, and you can't soak the compost or it'll rot, so you raise the humidity around the exposed part to reduce evaporation.
A clear plastic bag put down over the canes and the pot and taped into place will hold in the moisture, saving your cutting from drying out.
Common advice is to give it a gentle tug to see whether it's rooted, but I knew mine had when I saw them producing new leaves.
If you want to take things a step further in caring for the cutting, you can include a little water dish on top of the compost in the pot to raise the humidity.
You can also, if you're really going for it, stick a drinking straw into the bag and blow warm, moist, CO2-rich air into the bag every day. That might be going too far, but hey, it may help.