What exactly is Propagation?

What exactly is Propagation? It is the creation of plant specimens by natural processes from the parent stock.

There are two types of propagation - sexual and asexual.

Sexual propagation is drawing from the genes of the parents to create another plant. The floral parts of the plant are pollinated and seeds are created. Plants grown from seeds are a unique mix of the parents genetics. The resulting plants are all variable. Sexual propagation is growing from seeds or spores.

Asexual propagation is taking part of one parent plant and causing it to grow into a new plant.

Plants grown from asexual propagation are a genetic ‘carbon copy’ of the parent plant. The resulting plants are all identical. Asexual propagation techniques that you could do at home - division, cuttings, layering, grafting and budding.

To grow from seeds you either purchase seeds from a seed company or save the seeds from a plant in the garden.

There are two different types of seeds available from a seed company - open pollinated and hybrid seed.

Open pollinated seeds has been pollinated by any pollinators - bees, wasps, insects etc - and as a result has pollen from whatever plants the pollinator has visited included in the seed creation. There can be a wide range of genetic variability in the seeds that then grow into plants. Heirloom seed varieties are always open pollinated.

Hybrid seeds are developed in a controlled pollination situation where only the pollen from the two desired parents with the desired attributes ( pest and disease resistance, yield, vigour, flavour etc) is used for pollination.

The seeds are then grown to see what attributes they have. And this process is repeated and repeated until consistent results are produced and those seeds are then sold. The resulting plants should be very consistent and true to form. The downside with hybrid seeds is once planted in the garden and open to pollinators, the seed collected from them will not reproduce true to form. So to get the consistent results you have to continue buying the hybrid seeds. The time and effort that goes into creating the hybrid seeds is why they are more expensive than open pollinated seed.

To collect seeds, you simply need to let the plant bloom, be pollinated and to create a seed pod or fruit. You need to let the seeds mature on the plant - they generally turn brown or black and they dry out -you can often hear them rattling in the pod. At this point the plant will prepare to spread the seed so you will see the pods begin to crack open. This is the point where you cut off the stem with the seed pods on them, put them in a paper bag and leave it in a dry place for the seeds to fall out and collect in the bottom of the paper bag. Remember to label them so you know what you have saved and discard the stem and seed pod.

If you want to try hybridising your own seed, you have to choose two varieties of the same plant with the attributes you want ( flower colour, shape, size etc), and you have to exclude the pollinators, by netting or bagging the flowers before the buds open at all. You then have to act as pollinator, transferring the pollen between the two flowers with a paintbrush and then continue to keep the natural pollinators out of the flower until the seed pods have developed. Then you need to collect the seed as described above and grow the seeds to see what attributes and how they present have been shared amongst the baby plants.

Asexual propagation is used in the horticulture industry to obtain consistent plants that can be marketed and sold. The growth habit, the flower shape, colour and size etc are all the same as the parent plant because it is a direct genetic copy of that plant. This is also how a plant that is grown from seed and has all the desired attributes the grower wants is then reproduced. They can’t use seed to produce more plants as they will be variable to the parent plant so they use asexual propagation techniques to create identical plants.

The type of asexual propagation depends on the growth habit of the plant.

Division is the easiest of the techniques. It is commonly used for clumping plants such as herbaceous perennials -such as agapanthus, flax, daylilies and renga renga- and bulbs. It is typically carried out in winter or early spring (if the plant is frost tender). You can remove small divisions off the edge of the root ball or split it in half. Dig the plant carefully up, avoiding root damage, and place 2 sharp spades back to back in the rootball and force them apart.

Growing from a basic cutting involves taking a piece of a plants stem or branch and putting it in potting mix or water to grow roots. There are a few things you need to know; When you take the cutting you need to cut under a ‘node’ ( where a leaf attaches) at the bottom and just above a ‘node’ at the top. This is because growing hormones are located at these points and is where the roots or new growth will develop from. You need to remove all the leaves from the bottom half of the stem before you put it in potting mix or water. If the remaining leaves are large, cut them in half so the plant can still photosynthesis and feed itself while it is growing roots but not have too much greenery to keep alive. There are a number of different methods of taking cutting from different parts of the plant, depending upon the type of plant you are trying to grow.

Layering is where part of the parent plant - a stem or branch- is pegged down in contact with the soil while still being attached to the parent plant. The point that is pegged down will grow roots and at that point it can be severed from the parent plant to form its own plant. The most common version of this are the runners sent out by a strawberry plant.

Grafting is done to combine the attribute of the top - the flowers, growth habit or fruit - with the growth habit of the bottom ( the rootstock). A simple example is a grafted tomato. The tomato with its specific variety attributes eg Beefsteak, is grafted onto a gourd rootstock. The rootstock is much stronger than a tomatoes root system so the tomato plant grows faster and bigger than normal and produces the tomatoes faster than usual. It has a lot of benefits. Another example is to create a dwarf variety of fruit tree such as apple or citrus variety. The desired fruit is selected and the wood is grafted onto a weaker grower rootstock which means the tree will not grow as big or as strong while still producing fruit. It is important to note that if you ever see green leaves appearing from underneath the graft site ( the leaves of the rootstock) to remove them as soon as possible. If it starts to grow it will take the energy from the grafted material and cause it to weaken and die. Fruit trees and deciduous trees are commonly grafted.

Budding is very similar to grafting except instead of a piece of stem being grafted into the rootstock, a bud is removed from the mother plant that has the desirable attributes for the ‘top’ and is slipped under the bark of the rootstock where it attaches and begins to grow. Roses are a common example of budding being used.

Propagation is a really interesting skill to learn and develop and it is a useful way to gain new plants or add varieties to your garden at little or no cost. 

Written for Gubba by Kelly Jean Reyland from Garden Advice NZ (www.gardenadvice.co.nz)