Hardwood cuttings are probably one of the easiest way to propagate new plants, and are normally taken in the least busy time of the garden calendar: Late autumn - early winter. Taking hardwood cuttings is a technique that can be used for many different types of shrubs, but cannot normally be used for other plants.
The cuttings material is taken from shrubs, using the previous last season's ripe growth wood, and simply cutting the leafless stems into segments 6-8in (150 - 200mm) long. It is possible with some shrubs to take 3 or 4 cuttings from one stem.
Simply make your base cut just below an old leaf joint, and cut off the top of the cutting with a slanting cut, (You will then easily be able to recognise the top from the bottom of the cutting - sometimes difficult with some types of shrubs when not in leaf.) The top cut should be just above a leaf joint. It may help rooting if you make a slight wound in the bottom 1in (25mm) of the stem by cutting a sliver of bark away to the wood underneath.
On some stems, such as hollow stems (Forsythia) and pithy stems (Sambucus) it is best to just use the lower portion of the stem, with a bit of the older wood attached at the base. Maybe a 'heel' from the main branch. Dip the base of the hardwood cutting into hormone rooting powder.
The cuttings can either be inserted into the open ground, or into a deep pot in a sheltered spot or cold frame. If inserting into the open ground, then prepare a slit trench and fill the bottom couple of inches with a mixture of sharp sand and peat, or just sharp sand if it is a heavy clay-type soil. Insert so that the top bud (slanting cut) is around 1in above ground level.
The procedure for the hardwood cuttings is just the same if inserting into a pot and coldframe, but use a 50/50 mix of peat and sharp sand or grit.
The cuttings should root by spring - normally associated with the top bud breaking into leaf. Those planted in the open ground can either be left insitu until the following autumn and then lifted, or they can be carefully dug up after rooting and growing on in protected conditions until established. Pot planted hardwood cuttings can be carefully separated and re-potted once rooted.
If you are going to produce quite a number of cuttings, then a different option is to bundle the cuttings up and place in sharp sand in a cold frame for the winter. They can be completely covered with the sand. Place them into a prepared trench in early spring. It may well be that some of the cuttings will have rooted at this time.
Shrubs which can be grown by hardwood cutting include :-
Forsythia, Sambucus, Currants, Butterfly Bush, Spiraea, Azaleas - evergreen and deciduous, Privet, Mock Orange, Ribes, Cornus - Dogwood types, Weigela - weigelia, and so on.
There are also several trees that can be propagated by means of hardwood cuttings. These are normally restricted to Poplars, London Planes and Willows various.