Propagation is an interesting and rather addictive gardening practice … once you have achieved a few successes.
For the botanically minded, there are two types of propagation, the first being ‘sexual’ which is the creation of new plants via parts from two parent plants to create a third new plant.
This is probably familiar to most of us as the process of seed creation through pollination.
The offspring is a combination of the traits of both parent plants so, just like us humans, will not always be exactly the same as either parent but more likely a combination of the two.
The other type of propagation is ‘asexual’ and this is achieved via cuttings, division of plants, grafting, budding and layering of one parent plant and this will produce a clone.
The resulting plant is an exact copy of the parent plant in every way although mutations do sometimes occur.
Seeds
The trick to successful seed propagation is good seed stock to begin with and sowing as per requirement of the particular plant – simply throwing out a handful of seeds and hoping for the best really won’t cut it.
There also needs to be a bit of reality check as not all seeds are likely to germinate and not all seedlings will survive to become mature plants.
Buying Seeds
Always check the ‘sow by’ date on the packet and ensure that the seeds can be sown at the time you are thinking of planting them.
If you really must have that packet of seeds you have spied on your shopping trip, make sure the ‘sow by’ date still falls within the coming season and keep in a cool, dry, dark place until you are ready to use them.
It’s best that once opened, all are used.
Follow the directions given on the packet closely for the greatest success as some seeds have very different needs including the requirement to soak before use and sowing depths and mediums will also vary.
Seed Saving
Such an exciting thing to do because you may end up with plants very different from the parent plant you collected the seeds from in your garden.
For most plants, it is best to use healthy, strong plants and collect seed pods as soon as they change colour from whatever is ripe for them (usually green) to a dried brown to black.
Place indoors in a full sun position, out of the way of drafts and wait until fully dry.
Pods may release on their own or you can gently break open and (again) store seeds in a cool, dry, dark place until you wish to sow.
Cuttings
It’s not that all plants can’t be reproduced via cuttings, but some methods work better than others with different plants.
Types of Cuttings
Softwood cuttings are taken from new growth and as the name suggests, they are very soft.
They take really well either in water for later transplanting or in cutting and seed raising mixtures but are rather fickle with a low survival rate after striking.
Greenwood cuttings are created when the plant stems are a little past the softwood stage and can be recognised by firmer stems.
They have a better survival rate into maturity.
Semi-ripe cuttings work very well with conifers and most evergreens and are taken once the stems begin to bud.
Hard wood cuttings are made well before new growth begins when the plant is in a dormant phase.
These cuttings are slower to strike, don’t have as great a rate of striking but once they do take, have an excellent survival rate into maturity.
Leaf-bud cuttings are a semi-ripe cutting with a single leaf still attached and these are an economical way of creating an increased number of cuttings, especially from shrubs.
Full leaves develop roots from the picked end of the leaf and part leave cuttings will develop roots from the wound created from cutting them up.
Root cuttings are created from larger roots of suitable plants during their dormant phase.
Types of Stem Cutting Preparation
When obtaining cuttings, most are taken from the stem just below a node.
These joints in a ‘nodal cutting’ hold a lot of vascular tissue and so the formation of roots is far more likely.
Other methods include ‘heal cutting’ which involves pulling away side shoots so that some of the bark from the main stem comes away with it, ‘wounding’ a cutting by scraping away a section of the bark to expose the inner tissue and ‘callusing’ which is also a form of wounding in which a callus is encouraged to form from a scraped stem.
Root Hormone
To help your baby cutting along, you can apply a root hormone.
There are commercial preparations out there but I’m a fan of organic homemade so here’s one of my recipes:
1. Add one generous tablespoon of organic honey to 2 cups of boiling water and stir well – once it drops to room temperature it is ready.
2. Dip cutting end into the mixture and then plant in a seed and cutting soil raising mix.
I have also tried dipping hardwood cuttings into Vegemite and had success as well – as strange as it sounds it’s probably the Vitamin B boost that creates the magic!
Cutting and Seed Raising Mediums
Many cuttings can be started in a clear jar of water that sits in filtered light while seeds can be put straight into ordinary garden soil or a potting mix.
Planting straight into a speciality cutting and seed raising medium however gives the vast majority of plants the best beginning and makes transplanting into your garden or larger pots easier down the track.
Propagation mixes need to provide aeration, excellent drainage and support.
Although bagged commercial mixtures can be purchased, a good example of a homemade mix is: 2 parts coir peat, 2 parts compost and 1 part course river sand.
Bulbs, Corms, Tubers and Rhizomes
These are underground compressed stems that hold a bud within.
Many lay dormant between growing seasons until conditions suit their return as a new plant or they simply begin new growth at any time of the year depending on conditions.
Tubers can be either Root Tubers, that are formed from sections of root stock or Stem Tubers that, as you would guess, form from sections of modified stems.
Most can be separated carefully from the parent plant to create a new plant and some of the bulbs can be encouraged to further divide through chipping sections into separate scales, cutting segments that still contain the basal plate of the bulb or scoring, depending on the plant type.
Division
If you are a fan of Agapanthus (Agapanthus africanus), Dayliy (Hemerocallis spp.) or Shasta Daisy (Leucanthemum spp.) then you might already be aware that you can create new delights by easing in-between clumps of your plants and simply lifting out sections for replanting.
There are many plants that can be easily divided, and an indication is a clumping form in their growth pattern. Sometimes the clumps may need to be carefully cut with a sharp knife to release.
Layering
Many plants layer naturally when their stems touch the ground, prompting the stem to develop roots.
You can see this in plants like Ivy (Hedera spp.).
To copy this process, all you need to do is bend stems down onto the soil and peg down to encourage root formation.
For stems that cannot reach the soil, Air Layering can be used where a wound is made in the stem and then it is covered in compost and wrapped in moss.
Once roots form in either layering method, the stem is cut from the plant and transplanted.
Propagation Examples
These are not the only way to propagate these plants, but it gives you an idea of how you could start creating your own new plants at your place.
From seeds
Most annuals and perennials, Grevillea (Grevillea), Avocado (Persea).
From stem cuttings
Rosemary (Salvia rosmarinus), Pothos (Epipremnum aureum), Geranium (Pelagonium), Wattle (Acacia), Lemon (Citrus limon), Mulberry (Morus), Fuchsia (Fuchsia magellanica), Hibiscus (Hibiscus rosa-sinensis).
From leaf cuttings
African Violet (Saintpaulia ionantha), Flaming Katy (Kalanchoe).
Division
Peace Lily (Spathiphyllum wallisii), Boston Fern (Nephrolepis exaltata), Snake Plant (Sansevieria).
Spoil Layering
Spider Plant (Chlorophytum Cosomum), String of Pearls (Senecia rowleyanus), Ivy (Hedra)
THIS WEEK YOU COULD PLANT
Brussel sprouts, capsicum, chilli, climbing beans, eggplant, kale, kohlrabi, leeks, lettuce, mustard greens, okra, pumpkin, radish, rockmelon, rosella, spring onion, squash, sweet corn, watermelon, basil, chives, lemongrass, mint, rosemary, tarragon, amaranth, azaleas, camellias, grevilleas, marigolds, petunias, sunflowers
Cheralyn Darcey is a gardening author, community garden coordinator based at Lake Macquarie
Send your gardening questions, events and news to our editorial email.