There are various vegetative methods for propagating roses, for example, bud grafting onto a rootstock, air layering. Whether the parent is a species rose, modern hybrids or already grafted onto rootstock will influence the propagation method used.
Air layering is a method of propagating new trees and shrubs from stems still attached to the parent plant. It is one of the oldest forms of vegetative propagation, with records dating back to some 4000 years ago in China. In fact, its continued use in that country over the millennia has led to the traditional term ‘Chinese layering’.
It Is not the first method that springs to mind for propagating roses, being more commonly used for Magnolia and Citrus trees. The benefits of this technique for roses are: –
- It can be carried out in both spring and in late summer / early autumn. If only short notice is given that roses need to be propagated this could be essential
- The process is simpler for a novice gardener to carry out
- It is suitable for a wide range of rose types, including climbers, modern hybrid teas and species
How to air layer Roses
Before preparing the stem, get together the necessary equipment: –
- Secateurs and / or sharp knife
- Coir or sphagnum moss. I like to pre wet this whilst preparing the stem, but it may take longer to absorb water if it’s very dry to begin with.
- Black plastic or silver foil or hessian.
- Small plastic water bottle – cut a slit down one side from top to bottom, plus cut out a hole in the base just big enough for the stem to fit through. The slit needs to meet up with the hole so the bottle can be fitted to the stem.
- Ties, weather proof adhesive tape or twine – for holding the ‘package’ or bottle firmly onto the stem. Ties make it easier to remove and check on progress.
Notes
Light can encourage the growth of algae within the rooting ‘package’, which will damage the emerging roots. Black plastic is wrapped round to prevent sunlight entering. Silver foil is sometimes used for the same purpose.
Using a bottle isn’t essential. However, it makes it easier to keep the coir or moss packed around the rose stem during the rooting process. And when it comes to removing the rooted section from the parent, everything is kept tidily in place, preventing collateral damage to the new roots.
More eco-friendly alternatives to the above include wrapping the coir around with
- hessian
- scrap fabric
- used potting compost bags, cut into strips
- waxed cotton
One of the issues with only using fabric or hessian is that the they will themselves get wet when it rains and may cause algae growth or the stem to snap under the extra weight. Likewise when the weather is dry the package may need watering.
Preparing the stem
Choose an unpruned stem for preference. Straight stems are easier to prepare, but most importantly choose a healthy, vigorous stem.
If carrying out the process in spring, choose a stem of the previous season’s growth. In late summer/ early autumn use a hardening shoot (greenwood) stem of the current seasons growth.
About 6 inches behind the growing tip will be the section to be air layered. Remove all side shoots and leaves in this area, to leave 3-4 inches of bare stem. But leave the foliage on the stem above and below this section.
Girdle the stem at this point by carefully removing a ring of the outer layer about ½ inch wide to expose the cambium layer beneath. This will be harder to do in the spring. But care also needs to be taken in autumn not to break the stem when it is soft.
Girdling the stem encourages the build up of hormones and food in this area, which encourages the rooting process. Apply hormone rooting powder to the exposed stem. This gives an initial boost; the last thing needed is for the plant to ‘scab over’ the wounded area!
Next squeeze any excess water from the coir.
Otherwise take a couple of handfuls of coir and knead into a ball. Gently split the ball as if you were splitting an orange and wrap the two halves around the treated area of the rose stem. Gently knead them together again so the area is fully covered.
Then either wrap black plastic around the coir and secure with ties or tape at each end. It is important that the coir does not become waterlogged.
Or, if a bottle is being used, pack the coir into the bottle. Generally its easier not to overfill, but to add more once the bottle is around the stem.
Both the black plastic and the bottle retain enough moisture and warmth within. However, if the rose will take a while to root, then covering the bottle with black plastic will exclude sunlight.
Care during the propagation process
Roses propagated this way later in the season are unlikely to show much signs of roots until late the following spring. Those which are air layered in spring should show roots within a couple of months. But the layered stem will take at least a growing season to develop strong roots
However checking on progress is essential. Testing that the coir is damp, and that there is no algae is just as important as looking for signs of roots. Small white nodules on the stem are the early sign of root formation.
These regular checks are often easier to carry out if the bottle method has been used as it only needs to be slightly prised apparat rather than fully removed.
Removal of the air layered Rose from its Parent
The best time to remove the layered stem from the parent is in early spring, but the more important criteria is that there should be healthy and sufficient roots which are visible through the coir.
- Firstly prune off new growth above the air layered section (I like to leave on two sets of leaves above)
- Leave the coir on the roots
- Remove the covering
- Cut through the stem just below the rooted section
Getting the air layered Rose to successfully establish in to a soil based medium is probably the trickiest part of the process.
The roots have been used to growing in a much less dense media than soil and take time to adjust. A free draining potting compost is needed; John Innes no 1 or similar mix, using peat free alternatives.
Slightly loosen the coir. Place rooted layer into the pot, ensuring roots make contact with the potting compost without over firming which would compress and potentially damage the roots.
Water and label.
The new rose will need to be grown on in a pot until large enough to plant in the soil. It may benefit from being grown on in a protected environment until established. In which case it will need to be hardened off before planting out.
Marie Shallcross
Plews Garden Design and Consultancy; Gardening Lessons