Cuttings - The Basics
Cuttings are the simplest method of propagating most shrubs and herbaceous perennials.
It is also the surest way of propagating a new plant which is identical in all respects to the parent, which is not always the case with seed propagation.
This technique is known as Asexual Propagation, which relates to propagating by vegetative methods (Cuttings) as opposed to Sexual Propagation which is the art of propagating from seeds.
This method is also quite useful for propagating plants that produce sterile seeds, and can't be propagated by sexual methods.
Having said that there are a few principles that apply to all types of cuttings if success is to be achieved, among these is good hygene, the correct type of compost and the use of water.
The following details list these principles:
Hygiene is paramount when taking cuttings to ensure one does not transfer viruses from one plant to another.
Wipe cutting tools after taking cuttings from a plant and before taking cuttings from another!
Cutting tools should always be razor sharp to ensure that a clean cut is made each time you take a cutting.
Cuttings that have shredded / damaged ends can be problematic when it comes to the formation of roots.
Containers should be washed prior to their use.
The rooting compost should be fine in texture, of uniform consistency, yet well aerated and loose.
It should be free of insects, disease organisms, weeds, and weed seeds.
It should also be of low fertility and capable of holding moisture, yet have good drainage properties.
Do not use garden soil to root cuttings it is not sterile, it is too heavy, and it does not drain well.
Use a seed and / or cutting compost in preference to multi-purpose compost as the high levels of nutrients in the latter can inhibit the rooting.
Listed below are some alternative recipes;
1) Equal parts (by volume) Seived peat and sharp sand.
2) 3 parts (by volume) compost to 1 part Vermiculite, 1 part Perlite and 1 part silver sand.
3) 2 parts (by volume) compost plus one part silver sand.
Compost / Sand Ratio
The keen amateur gardener when making his/her own compost may be faced with the difficulty of how to sterilise the ingredients.
There are a number of small electric sterilising units available on the market, but the amount of compost being made may not justify the cost of such a unit.
As an alternative small amounts of the ingredients may be sterilised in a domestic steamer.
To do this, fill the steamer no more than 150mm(6") deep.
Raise the temperature around 80°C (180°F) and sterilise the soil for ten minutes.
Once sterilised, rapidly cool the steamer by dipping it in ice cold water.
Once cooled the compost is ready for use!
Once cuttings are severed from the plant they build up auxins at their base, it is this plant hormone that promotes the formation of roots.
In interest of good hygiene, when using hormone powder/gel, tip out a small amount of the mixture into a small container, such as an old lid or plant pot saucer, and dip the base of each cutting in this.
Throw any excess away after use.
This method eliminates the risk of contaminating the remaining contents of the container, thus avoiding the possibility of passing on viruses and/or other diseases onto future cuttings.
Most rooting powders / gels have a short shelf life and should be replaced annually.
Cuttings taken in summer are generally rooted in a cold greenhouse or cold frame.
Winter taken cuttings will require some form of heat e.g. a propagator (these can be purpose made or home made).
To root cutting you need the following conditions;
Cuttings should not be subjected to too much sunlight.
If unavoidable provide some shading to keep the leaves cool, but not so much that it greatly reduces photosynthesis.
Aim to provide a compost temperature of 15°-25°C (60°-75°F) but no higher, as above this root production can be suppressed.
The temperature around the foliage should be cooler than the compost.
Root formation requires the cells to grow and divide therefore the rooting medium should be sterile, well-drained and moist, yet able to hold moisture and allow the passage of air through it.
If cuttings wilt, this generally a sign that very little photosynthesis is taking place, so transfer cuttings to an area with higher humidity and better light levels.
Normally there should be sufficient moisture available in the container until rooting has taken place providing the container was well watered when the cuttings were first inserted.
Having said that, be careful not to overdo the spraying as over watering can be a major cause of failure.
A useful tip when spraying is to mix a fungicide and weak foliar feed to the water, this will reduce the chances of the cuttings damping off, plus it will supply some sustenance to the cuttings.
High humidity levels can also cause fungal rots so judicious ventilation will be required during the rooting process.
d) Other factors:
The compost should never be allowed to get too wet.
Avoid small cuttings these tend to exhaust their food reserves before they have rooted.
To reduce the risk of cuttings damping off, dip the prepared cutting in a fungicide solution prior to inserting it into the compost.
Wipe excess condensation of these lids daily.
Alternatively, if only rooting a few cuttings in a pot or small tray place the container in a polythene bag supported on wire or sticks and sealed with an elastic band.
Keep cuttings out of direct sunlight to avoid scorching and overheating.
Once cuttings show signs of growth, gradually increase the ventilation.
If using the plastic bag method puncture the polythene and remove the elastic band.
The whole bag can be removed about a week or so later.
When the cuttings are well-rooted*, transplant them into individual pots of potting compost as soon as possible.
* This is often seen as roots protruding from the base of the container or the foliage is looking a fresher shade of green.
Cuttings rooted in the autumn should be left until March before potting on.
Transplanting cuttings in the dormant season can kill them.
Grow plants on in progressively larger pots until they are enough to plant out.