Five Ways to Make New Plants

Sowing seeds is the most common way of propagating plants in the food garden, but there are other ways of making one food plant into many food plants. This blog post looks at five plant propagation methods that are effective and commonly used in the food garden.

Five propagation methods that are commonly used in Tasmanian food gardens:

1. Sowing - used for annual vegetables because sowing is easy, fast and reliable.
2. Division - used for rhubarb, mint, chives because it delivers a faster result than sowing.
3. Striking - a twig cut off a perennial plant is put in water or soil and develops roots. 
4. Grafting - a twig of one fruit tree is attached to another compatible fruit tree.
5. Layering - a low stem is bent down into to the ground so it forms its own roots.

These propagation methods are discussed below in more detail.

Sowing

A new plant is grown from seed that comes from pollination of the flowers of one plant with pollen from another plant. Pollination combines genetic material from one plant with genetic material from another plant. The result is a new plant with characteristics influenced by both parent plants.

Most food garden plants are annuals. Sowing is the most commonly used method of propagation in the food garden. In theory one can use some of the other methods of propagation for annual vegetables, but usually there is no need to.

Sowing is very different from the other four propagation methods mentioned above in one very important aspect. The result of Method 2-5 is a plant that is genetically identical to its parent plant! 

Method 2-5 are used in the plant-breeding industry to produce plants that are identical to their parent plant. 

Plant breeders use Method 1 if they want to improve the characteristics of a plant variety.

We home gardeners use, in most cases, what gives us a good result without too much effort.

You can find more helpful information about sowing in Food Garden Group blog posts Sowing in Your Garden and Sowing in Pots and Punnets.

Striking

A stem or leaf is cut off a perennial parent plant and new roots form if it is put in water or soil. Striking cuttings is used for many kitchen herbs, for instance Mint, Rosemary, Thyme, Sage, Lemon Balm and Tarragon. Propagating a perennial herb will in most cases give a good size new plant much faster than if you grew it from seed.

The trick is to choose the right cuttings at the right time of year. 

The right cutting is wood that is not too old and not too new.  It 'snaps off cleanly' when you bend it.  It is not green, and it is not old and stringy.

The best time of year to propagate is when growth is at its strongest, that is in spring.  Summer is fine too, but if you try to 'strike a cutting' in autumn or winter, it more often fails.

Some stems will quickly and easily form roots in water, but many plant varieties take 2 to 3 months to form new roots and the water the stems are sitting in, will in many cases begin to ferment and become smelly. A more reliable method is to put the stems in sand. The method for doing this is described below under the heading Striking Cuttings - Step by Step.

Grafting 

A twig or bud of one plant variety is attached to another closely related variety, so the two varieties share one root system, but produce different varieties of fruit. 

In theory grafting can be done on many veggie garden plants, but the reality is that home gardeners mostly use it for getting more than one variety of fruit on fruit trees. 

Grafting saves space as it enables you to grow multiple varieties of a particular fruit on one tree in one spot in the garden. New fruit trees can be grown from seed, but this will take years longer, with no real certainty that the new tree will produce fruit that is as good as that of its parent trees.

Basic grafting techniques are explained in A Look at Grafting on this blog.

Division

An established perennial plant is divided into smaller sections that have or form their own roots.

Rhubarb is a good example of a food garden plant that is in most cases divided, rather than sown, because dividing is easy and successful in most cases. You will get rhubarb stems off your new rhubarb plant much sooner than if you sow rhubarb seed. 

Mint, Chives and Thyme are other examples of food garden plants that can successfully be divided.

I recently dug out our Yacon plants (see Fruit & Vegetables from South America). I carefully divided the rhizomes (on the right in the photo below) and planted those. The result will be multiple new plants next season coming from this season's one parent plant (the photo on the left). The brown tubers we ate! 

 

  

Layering

A lower branch of a plant is bent down to the ground, then covered with soil while still attached to the parent plant, in the hope that it will form its own roots. Tent pegs or similar are often used to make sure this section of the stem stays in the ground and doesn't move in the wind. After a few months, and if the stem is still alive and healthy, the stem is carefully separated from the parent plant. 

You may think that layering is just another technique invented by humans, but you would be wrong in that. Strawberry plants send out long flexible branches that bend towards the ground. Once a long branch reached the ground, roots at the end of the branch go into the soil and next season a new strawberry plant with exactly the DNA of its parent joins the strawberry field.

Layering is used by humans for plants that have low long branches that bend easily. It is commonly used for berry varieties such as Blackberries (and other similar berries), Red and Black Currants. 

Layering is used because it creates a productive new plant much faster than if that plant's seed was sown.

Striking cuttings - step by step

How many cuttings - Decide how many new plants would you ideally like.  Not all of your cuttings might be a success, so it is generally a good idea to make more cuttings than new plants that you actually need.  Also, consider how many suitable cuttings you can take from the plant without doing too much damage to it.  

Choose a pot - this may be a surprise, but one cutting on its own in a large pot with plenty of growing medium around it is less likely to strike than many cuttings together in one small pot with limited space per cutting, so choose a pot in which you will just be able to fit the number of cuttings you have.  If you only have one cutting, choose the narrowest pot you have.  Pots need to be 'nice and deep' so a large area of the cutting(s) will touch the growing medium.

Choose a pot in which all your cuttings just fit

Prepare growing medium - thoroughly mix 1 part of coir with 3 parts of clean coarse sand, then fill the pot with the mix. Add water until it begins to come out of the bottom of the pot.  The mix is now damp, and you know that surplus water can escape.

Coarse sand and the bag it came in

Prepare the cuttings - the right cutting will 'snap off' cleanly. It is not green and it is not old and stringy. Strip all leaves and flowers off, except at the top, ie. 90% of the foliage.  This will limit evaporation and encourage root growth.  Make sure it is a clean cut.  If it is not, take another bit off with a clean pair of scissors or secateurs.  Don't let cuttings dry out.  If you don't have time to do the next step below immediately, put the cuttings in a plastic bag in a shady spot with some water added to the bag.

Consider using rooting hormone - In many cases cuttings will form roots without the use of rooting hormone, but applying it to cuttings increases the chances of success.  Some people cover the bottom half of cuttings with honey.  Honey has antiseptic qualities, so it will help the cutting to stay healthy, but it is not a rooting hormone. 

Rooting hormones actively encourage cuttings to make roots. You can make your own rooting hormone mix from willow twigs.   Cut young willow branches into a handful of small sticks that are just a bit shorter than the height of the jar you are going to put them in. You may like to take the leaves off, but this is not essential. Put the sticks in the jar, then fill the jar with boiling water. Leave this to steep until the water has cooled down (see photo below). Then put cuttings you want to strike in the jar for a few minutes. Thank you, Christina G. for this information!!

Hormone rooting powder can also be bought as a ready-to-use product at nurseries and hardware stores. 

Put the cuttings in the pot - dip the bottom of each stem in honey or rooting hormone, if you decided to use this. Then, with a stick make a deep hole in your pot and insert the cutting, so only the top leaves are above soil level. Repeat this process until you have many cuttings in one small pot with limited space per cutting.

Find a good spot for the pot - put the pot in a sheltered position away from direct sunlight. Ideally keep pots 'cool on top and warm (but not hot) on bottom'. Do not fertilise the cuttings in any way. Make sure the growing medium is always damp, but make sure surplus water can escape. 

How long before they have roots? - over the following weeks observe the foliage you left on each cutting. Does it maintain a healthy colour, or is it fading, or even falling off? You need to give the cuttings time to develop a root system that will allow them to feed themselves after transplanting to a bigger pot. How long that is, depends on the plant variety, temperature, availability of water and season, but six weeks is probably the very minimum. Striking Rosemary cuttings took me 3 ½ months, so don't be too impatient!

Transplanting to a bigger pot - carefully put your fingers between the cuttings on top of the pot, then turn the pot over, rest it upside down on your hand, and lightly tap its bottom. The growing medium + cuttings should come out easily without damaging any roots. You can now separate each cutting and see whether roots have formed. In new pots prepare potting soil. For a good recipe to make your own seed raising/potting soil mix see blog post Sowing in Pots and Punnets on this blog. The cuttings will need a good potting soil to grow into a healthy new plant.

My experiences with this method - The cuttings in the photo at the start of this blog post I put in growing medium at the start of October (Spring, the best time to do this).  After making sure the pot never went dry, I carefully took out the cuttings in mid January (3 ½ months later) and found what you see in the photo below:

All cuttings had formed roots. Some more than others. I gently planted each cutting in its own tall small pot with a light soil mix, watered them, and then put them in a shady spot outside.  I will try to make sure the soil in these pots remains moist at all times.

Many thanks to Food Garden Group member Jan R. for sharing her knowledge on striking cuttings!!

Cheers,

Max Bee