Plant Propagation

At some stage of your growing journey you will be keen to try your hand at propagation. There are lots of reasons – perhaps someone you know has a lovely plant growing and you can’t find it in a nursery. Or perhaps you might be the one to have that lovely plant and would like to strike some cuttings to give away to a friend who has always admired it. Maybe you’d like to get a number of plants growing to save you money from buying them all – or – maybe you’re even just up for a challenge and want to try something new!

There are a few basic elements of plant reproduction that we need to look at – so Let’s talk about sex! Sexual reproduction of plants occurs when the female part of the flower is fertilised (through pollination) and the plant then sets seed. This seed contains the genetic material from both male and female flowers, so every seedling grown from these seeds will show characteristics of its lineage but will have individual variances. This occurs naturally, but can be exploited by human intervention and deliberate interbreeding. This is why we have such a wide range of variability within the same species of a plant.

This makes saving seed from your healthiest, best tasting and best performing vegetables a great thing to do. Plants evolve to be specifically suited to conditions and climate, so you can produce your own hardy and reliable strains of your favourite plants this way. Most annual plants reproduce sexually – so most vegetables fall into this category.
The other method of plant propagation is ‘asexual’. This involves making an exact duplicate of the parent plant’s genetic material by grafting, layering, cuttings or root division. Many perennial herbs and shrubs are propagated by at least one of these methods.

For home gardeners, saving your own seed, taking cuttings or dividing clumps of plants by the roots are the most common ways to propagate. These methods don’t require specialised or expensive equipment and can be achieved with a little practise and some trial and error.

Some plants strike best from ‘softwood’ cuttings (the soft, young growth tips of plants); ‘hardwood’ cuttings (more mature ‘branch’ material that is generally not flexible) or ‘semi-hardwood’ cuttings (somewhere in between the two – generally more ‘branch like’ in appearance, but still flexible). Again a good gardening book will have advice on whether to use soft/hard/semi-hardwood cuttings – and it can vary depending on time of year.

Timing.

As the saying goes, timing is everything. Many plants can be successfully propagated IF you take cuttings at the right time of year. A good gardening book will recommend the season to achieve the best strike rate. The same applies to germinating seeds. By all means, experiment and push the boundaries, but working with nature’s seasons will always bring you better results. Some gardeners also follow moon planting guides – and they swear by the results.

Temperature.

Plants have their optimal temperatures for seed germination or striking roots from cuttings. You can control the environment with greenhouses or heated beds. (Some ingenious ideas are out there for simple DIY versions, if you are looking at small scale home growing.) Ideal propagation temperatures quoted in books mean soil temperatures – which usually are lower than air temperatures. A good way to approach sowing seeds is to do a few at a time. By taking a ‘batch’ approach you are not gambling all your seeds at once if weather is changeable (as it often can be in early spring and autumn; the most common seasons for raising seedlings).   (Step 3 shown at right)

Moisture.

Seed germination, and a successful cutting strike rate, rely on adequate moisture - not too little and not too much. Excess moisture (in the soil and in the air) is one of the major causes of fungal disease or ‘dampening off disease’. Watering by a misting system (or even a hand trigger bottle) is a good way to provide moisture in small amounts, but at regular intervals. Ensure good airflow, and make sure the water you use is good quality – excessive salt or minerals in water can affect results.

Hygiene.

To avoid the spread of disease, always propagate from healthy plant material. Use a good quality seed raising or propagation mix. These are especially formulated to have the right balance of water holding and air flow, and to allow roots to easily penetrate between light particles. Keep secateurs sharp and clean. Wipe blades down with tea tree oil between uses, or if going from plant to plant to take cuttings. Wash seedling trays and pots before use – scrub them in water to remove built up dirt, then wash thoroughly in a diluted bleach solution (1:10 bleach to water) and allow to dry.  (Step 4 shown at right)

Root forming hormones.

These are often used to encourage cuttings to strike roots more quickly. While not essential, some plants will have a much higher strike rate with their use. Available as powder, liquid or gel. (Some growers prefer one or the other for different uses – but if you are just starting out; use whatever you can find. I don’t think it’s critical.) Many organic growers like to use honey, which has anti-bacterial qualities to help heal cuttings.

Basic steps for taking cuttings:

•Step 1. Take tip cuttings allowing 4 – 6 nodes (leaf growth points) on each one.
•Step 2 Remove lower leaves with fine pointed secateurs or fingers – causing as little damage to the cutting as possible. Any wound can increase the chance of disease.
•Step 3. Trim back top leaf growth. Remove young leaves and cut older leaves back by roughly 50%. This reduces the amount of water lost through leaves by transpiration.
•Step 4. Dip bottom stem in rooting hormone.
•Step 5. Use a pencil to create a small hole in your pre-dampened propagation mix, about 3cms deep – enough to cover the two lower nodes well; but you don’t want to go too deep.
•Step 6. Firm around cutting with soil, and water with a gentle rose spray. (Step 6 shown at right)
•Step 7. Leave in a warm spot with good light but not direct sunlight and check daily. Water as needed – but probably at least once per day. Use a mister spray or watering can with a gentle rose.

Providing cuttings remain healthy looking, you can assume roots will be developing. You can lift up the seedling tray after a couple of weeks and if you’re lucky, you may see fine roots protruding. Otherwise give a cutting a gentle tug. If you feel resistance, you know roots have begun to form. Gentle investigation of the root formation will indicate when the cuttings are ready for transplant. (Root growth approx 4 weeks shown at right)

Often, top growth will be starting to appear on the cutting.

These photos are showing taking softwood cuttings from a Kangaroo Apple (Solanum aviculare). (Cutting at approx 9 weeks shown below)

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