Start your stem-cuttings strong for the new year

SINGAPORE – Propagating plants from stem-cuttings is a popular technique, as it produces new plants that are genetically identical to their parent plants and requires less time than starting from seeds. The seed method also results in plants with genetics and characteristics that differ from their parents.

Creating new plants from cuttings is a beginner-friendly activity for all. For children, a stem-cutting is a fun “starter plant” that is more gratifying than tending a pot of soil with unseen seeds. For the elderly, this can create a sense of nostalgia and help them maintain fine motor skills.

What plants are suitable for propagation by stem-cuttings? 

Most plants that produce stems can be multiplied this way. Fellow gardeners or online resources will be able to provide more insight into the ease of propagation for specific species.

For any stem-cutting to succeed, the ability to produce roots is essential, as roots absorb water and nutrients.

Some plants are difficult to propagate from stem-cuttings, as they either produce no roots or take a long time to do so. For such species, other methods may be more suitable: air-layering, also known as marcotting; grafting; and, in rare cases, the use of tissue culture. These methods typically require more specialised skills and resources.

Types of stems to use

The types of stems used for propagation depend on the parent plant’s growth stage. Stem types can be split into two main categories: tip cuttings and internodal cuttings.

Tip cuttings refer to a stem portion consisting of a plant’s new growing point. This part of the stem is green and tender, and wilts easily. Such cuttings are often known as non-woody, soft-stem cuttings.

Tip cuttings will root more easily as they contain more growth hormones. Many herbaceous plants, such as culinary herbs like mint and basil, have high success rates when propagated from tip cuttings.

Internodal cuttings come from a portion of the stem between leaf joints, also known as nodes on a plant. Such cuttings can be softwood, semi-hardwood or hardwood, depending on how green or woody they are.

The woodier the stem, the longer it will take to root. Some gardeners use rooting hormones, sold in nurseries, to encourage root development. Plants that can be raised from internodal cuttings include cassava, drumstick tree and mulberry. 

Foliage plants such as aroids – which include plants from the genera Monstera, Philodendron and Epipremnum – can be propagated from both tip and internodal cuttings.

Rooting in water

Rooting stem-cuttings in water is common, especially for tip cuttings that wilt easily. This can be done in a clear container which allows you to monitor progress. Change the water at least once weekly to reduce the likelihood of mosquito breeding and refresh the oxygen for the cuttings. Anti-mosquito breeding pellets can be included.

Stem-cuttings that have rooted in water can be transferred to a growing mix of your choice, but expect some wilting, as roots produced in water may not be able to acclimatise to soil immediately. An adjustment period is needed.

Ensure the potted cuttings are in a cool, humid and semi-shaded area that is protected from excessive moisture loss.

Propagation medium

Use a sterile propagating medium so your plant does not suffer from pests and diseases. Standard garden soil may be unsuitable for propagation, as it contains pests and pathogens, and its clay-like consistency may lead to aeration and drainage issues.

My preferred propagating mix comprises equal parts vermiculite, perlite and fine expanded clay pellets. The particle size of each component ranges from 1 to 4 mm in size. Particle size determines the porosity of the mix and, in turn, affects moisture retention, aeration and drainage properties. It should not be soggy for prolonged periods or dry out too quickly. 

How to propagate

Choose a healthy stem that is not flowering or fruiting, ensuring that it has at least four to five growth nodes. Use sharp, sterilised cutting tools to snip the stem.

Ensure the stems on the parent plant and the cutting both end with a node, the point where a leaf meets the stem. Wounds heal best at a node. 

Prepare the cutting

Remove leaves from the lower two to three nodes of the cutting. This bare part of the stem will be buried in the propagation mix. Any leaves left on the stem will rot when buried in the mix. You may want to cut large leaves in half to reduce water loss. 

Plant it 

Prepare a pot of your chosen propagation mix and water thoroughly to force out large air pockets. Use a disposable chopstick to make a hole before planting the cutting.

Once planted, gently press down the propagation mix around the cutting so there is stability at the base and the cutting is properly embedded in the mix. As an added measure, water it again to ensure the cutting is in close contact with the growing mix.

Create an enclosure

For tip cuttings that wilt easily or have large leaves, put them in a clear plastic bag or disposable drink cup. Make several small holes in these enclosures to reduce heat build-up and allow air circulation. An excessively humid interior can lead to rot and disease.

Care

Keep the propagation medium moist but not soggy, and place the plant in a location that is cool and bright but not windy. You can also place your pots under grow lights indoors.

Stem-cuttings produce roots at different rates. Some plants root within a week, while others take months. Check for signs of root production by gently tugging the cuttings. If you feel a slight resistance, it means fine roots have been produced and are starting to anchor the cutting in the propagation mix. If it comes out easily, it has not rooted yet.

Acclimatisation

Once the cutting has produced roots and stems have shown new green growth, the plastic enclosure can be opened slowly in a process called hardening. This allows the cutting to adapt to the external environment. Leaves and tender growth should not wilt when hardened. 

The hardened cutting can be allowed to grow if there is still space in the pot. It can also be transferred into a new pot to grow on its own and moved gradually to its final location.