One of the easiest propagation techniques is propagating using hardwood cuttings. Since these cuttings don’t have leaves, there isn’t the initial requirement to provide a high humidity environment to stop the cuttings drying out before they root.
I’ve discussed the basic theory of how plants can be propagated from cuttings in the article "Propagating Herbaceous Plants from Cuttings", so I’ll go straight into practical instructions here.
Hardwood cuttings are even simpler to prepare than herbaceous cuttings, as we use cuttings from dormant deciduous trees and woody plants, and this technique is very useful for propagating fruit trees such as figs, pomegranates, mulberries and quince. Some plums can grow well from hardwood cuttings too, while other’s don’t do so well, it depends on the variety.
This technique is also used for propagating vines such as grapes and kiwi fruit, and the currant family – blackcurrants, redcurrants, golden currants and gooseberries.
The steps are as follows:
Step 1 – Select suitable cuttings
Hardwood cuttings are taken from deciduous trees and plants (ones that lose their leaves in winter) when they are dormant, i.e. when they have no leaves.
The best time for taking hardwood cuttings is from early autumn when the leaves drop to late winter.
Take cuttings that are close to pencil-thickness from current season’s growth – it will be mature and woody, not soft and green. Cut off any unripened green growth at the tips.
To increase the chances of rooting cuttings:
- Try to take cuttings where the current season’s wood (1 year old wood) joins the two year old wood. The base of the stem at this junction has the greatest potential for root development – it contains a large number of dormant buds that supply hormones required for developing roots.
- Take cuttings at leaf fall and just before the buds break.
Step 2 – Trim cuttings to size
Hardwood cuttings are cut much longer than herbaceous cuttings because they take more time to develop roots and therefore need to use the reserves of food stored in the cutting to keep them alive through winter. A longer cutting stores more food in it.
- Make a horizontal cut 6mm (1/4”) below the lowest bud at the base.
- Find a bud approximately 15-20cm (6-10”) away from the base to make the tip cut.
- Near this tip bud, make a sloping cut away from a bud, 6mm (1/4”) above the bud.
Step 3 – “Wounding” the cuttings
Species difficult to root should be “wounded” as this helps encourage rooting. This involves making an additional light cut on either side of the cut stem at the base to expose more of the cambium.
The cambium is the light green layer you see under bark when you scrape it away, before you get to the wood, this is a single layer of meristem tissue. Wounding also helps in some cases to remove a physical barrier which may be getting in the way of roots forming.
You can scrape off the bark or outer layer to expose the cambium using a knife of the sharp edge of your scissors or secateurs.
Step 4 – Dip the base of the cutting into rooting hormone (optional)
Treating cuttings with rooting hormone can increase the chances of stimulating root growth. This is more critical in plants that are more difficult to root.
Simply dip the base into the rooting hormone, that’s all!
If using root hormone powder, and be sure to tap the cuttings to remove excess powder.
Step 5 – Prepare propagating medium and insert cutting
The cuttings can either be placed in the ground in a ‘slit trench’ outside, or they can be placed in a container of propagating medium.
The cuttings can still lose moisture and dry out, even without leaves, so we try to place as much of the cutting below the surface of the soil, while allowing top 3 buds at the tip to be sitting above the soil level. Leaving 1/4 to 1/3 of the tip of the cutting above the surface achieves this, otherwise just leave three buds unburied.
Slit trench method:
- Make a ‘slit trench’ by pushing a spade into soil and rocking it back and forth. In clay soil, add some coarse sand for drainage.
- Put cuttings in so 2/3 is below the soil, place cuttings 5cm (2”) apart and press the soil down around them. If using multiple rows of slit trenches, place rows 30cm (12”) apart.
- Water in the soil around the cuttings. The soil will remain damp over the winter period. Cuttings will root and be ready to plant next autumn.
Container and propagating medium method:
- Fill a container (pot) with a suitable propagating medium. Materials commonly used as propagating medium are coarse sand, regular potting mix, coconut coir, or blends such as a mixture of one part peat and one part Perlite (by volume), or one part peat and one part sand (by volume).
- Put cuttings in so 2/3 is below the soil, place cuttings 5cm (2”) apart and press the propagating medium down around them.
- Water in the soil around the cuttings. Keep the propagating medium slightly damp but do not overwater as this will cause the cuttings to rot. If possible, place the container in a cold frame of greenhouse to speed up the formation of roots. The cuttings will be ready to transplant in spring.
Propagating Grape Vines
Grape vines have a slightly different technique for hardwood propagation, so I will detail it here.
To propagate grape vines, simply take a cutting with 3-4 buds, and push into the propagating medium so that only two buds are unburied.
You can also take very short cuttings containing only one bud known as “vine eyes”. Make a cut 6mm (1/4”) above a bud, then make another cut 5cm (2”) below it to complete the cutting.
Note: vine eye cuttings with their single bud only do not take root as easily as the larger 3-4 bud cuttings.
You can put many vine cuttings into a single container, and then pot them up separately when thy put their leaves out in spring. It is advisable to let them grow in their pots for a year to develop strong roots, then they can be transplanted in the following spring.
As you can see, this technique is very simple, and you can use all the cuttings left over from the winter pruning of fruit trees to propagate more trees. Its better than tossing out, mulching or composting the prunings, and if the cuttings fail, then you can do that. At best, you’ll end up with more trees to plant in your garden, or to give away to others.