One thing a growing garden needs is plants, and lots of them! To buy enough plants to fill a regular backyard garden can be quite an expensive affair…
But, thankfully, it doesn’t have to be that way, since nature provides for us freely and abundantly, and when we work with nature, it becomes quite effortless, and inexpensive too!
Plants naturally reproduce themselves, and they are more than capable of doing this without any help. We can take advantage of some of the mechanisms by which plants can reproduce themselves to produce an abundance of plants for our gardens.
Many herbaceous plants (plants that do not have a persistent woody stem) and even many woody stemmed plants can be reproduced if a “cutting”, a short length of the stem or a branch that is cut off, is put into moist ground in a partly shady cool spot. In time this cutting will sprout roots and become a new plant that is an exact genetic clone of the plant the cutting was taken from.
Softwood vs. Hardwood Cuttings
At this point you may be wondering what the difference is between taking hardwood and softwood cuttings.
- Softwood cuttings are taken during the growing season, where the plants have leaves, so an important consideration is to maintain the humidity levels until roots begin to form to prevent the cuttings drying out.
- Hardwood cuttings are taken in winter, during dormancy, when all leaves have fallen.
When discussing propagating plants by cuttings, the question inevitably comes up – why not grow from seed?
The Difference Between Cuttings and Seed Grown Plants
The difference between growing plants from seed and growing plants from cuttings is genetic variation. As just mentioned, cuttings are identical genetic clones of the parent plant because this is vegetative, or asexual reproduction, as genes only come from one parent. Seeds can produce plants that are different from the parent plants because seeds are produced by sexual reproduction, they receive genes from a male and female to form. As they are a cross from two sets of genes, many fruit trees are not “true to seed”, that is, their seeds will produce a different variety of tree from the parent. For the botany purists, yes, there are some exceptions, but this is generally the case.
For example, the seeds from a particular variety apple will not grow to be the same variety as the apple tree they came from. The seeds will produce a wide variety of different apple tree types.
So what you may say? Well, consider that not all the varieties of apple would taste good, some may not be palatable or edible at all!
Why do plants do this, mix and match their genetic material and constantly change? Simply, to adapt to different conditions and enhance their chances of survival and reproduction. Now it should be clear why all commercial fruit tree varieties are grafted, the roots may vary slightly but the top parts that are grafted on top of the rootstock all come from the same original parent plant.
The other great things about cuttings is that the plant produced from a cutting has the same genetic maturity as the parent plant. So, if a plant takes three years to produce fruit when it’s grown from seed, a plant grown from a cutting will be mature if the parent plant is, so a new plant produced from a cutting of a three year old plant will fruit in the same year. This saves a lot of waiting around…
Genetic variation isn’t as big an issue with most herbaceous plants, but you can maintain the variety if it has favourable characteristics, and it’s a great way to produce hardy, mature plants in a hurry.
Now that we’ve covered the basic theory, lets get down to a practical example of how to propagate plats from cuttings:
Procedures for Rooting Softwood Stem Cuttings
Step 1 – Select suitable cutting
Most herbaceous (softwood) stem cuttings are best taken during the growing season of a plant, from Spring to Summer, and the best time is early morning, when the plant tissues contain the most water.
- It is important to keep the cuttings cool and moist until they are placed into the propagating medium. When working with cuttings, don’t lay them out exposed to full sunlight, work in a shady spot!
- If they need to be transported, wrap them in a moist paper towel in a plastic bag. If there is a significant delay potting up the cuttings, they can be stored in a plastic bag in the refrigerator.
Cuttings are usually about 10-15cm (4-6”) long, from current or past season’s growth. Cut below a leaf joint. If possible, choose strong, healthy, disease-free shoot for a cutting, preferably from the upper part of the plant.
- Avoid taking cuttings from plants that show symptoms of mineral deficiencies.
- Avoid taking cuttings from plants that have been heavily fertilized, especially with nitrogen, as they may not root well.
- Avoid taking cuttings from plants that show moisture stress.
Step 2 – Strip off lower leaves
Remove the leaves from the lower one-third to one-half
(1/3 – 1/2) of the cutting to leave a bare stem.
This allows the lower portion of cutting to be inserted into the propagating medium, and also reduces the amount of leaves from which moisture can be lost. If too much moisture is lost, the cutting will dry out. Remember, the cutting doesn’t have any roots yet to pull up more water to replace any it loses!
- On some plants you can strip off the leaves easily by holding the top of the cutting firmly with one hand, then using the other hand to pinch the lower part of the cutting and pulling gently downwards. If this doesn’t work, trim the leaves away with scissors or secateurs.
- On large leafed plants, cut all the leaves in half by trimming the ends off to reduce water loss. This also reduces the size of the cuttings so they take up less space. The added advantage is that you can tell when new growth emerges because you’ll see uncut leaves, which is an indicator that the cutting has rooted and is growing!
- Remove any flowers and flower buds when preparing cuttings so the cutting’s energy can be used in producing new roots rather than flowers.
Step 3 – Cut stem below a leaf mode
Cut the stem about 6mm (1/4”) below the lowest leaf node on the cutting.
To identify the leaf nodes, look for the areas where the leaves grow out from, so this will be an area where you removed the leaved from earlier. If the area has no leaves, it may have buds where new leaves will grow.
- The reason why we cut near the leaf nodes is because these areas contain a large area of meristem tissue. Meristem cells are undifferentiated calls, similar to human stem cells, that can grow and divide to form various kinds of cells for plant growth, including roots.
- The cells in the meristem divide quickly and form callus to seal the end of the cutting, and then under the influence of the plant’s own hormones, auxin and cytokinin, these callus cells differentiate and become root cells
Species difficult to root should be “wounded” as this helps encourage rooting. This involves making an additional light cut on either side of the cut stem at the base to expose more of the cambium.
- The cambium is the light green layer you see under bark when you scrape it away, before you get to the wood, this is a single layer of meristem tissue. Wounding also helps in some cases to remove a physical barrier which may be getting in the way of roots forming.
- You can scrape off the bark or outer layer to expose the cambium using a knife of the sharp edge of your scissors or secateurs.
Step 4 – Dip cut end into rooting hormone (optional)
Treating cuttings with rooting hormone can increase the chances of stimulating root growth. This is more critical in plants that are more difficult to root.
If using root hormone powder, be sure to tap the cuttings to remove excess.
- Most commercially available rooting hormone products consist if two synthetic auxins (plant hormones), indole-3-butyric acid ("IBA") and naphthaleneacetic acid ("NAA"), discovered in 1935. They have similar functions to the auxin naturally produced by plants, indole-3-acetic acid ("IAA") which was first identified in 1934, and are more effective in promoting root formation. Afterwards IBA was also found to be naturally occurring in plants.
- Rooting hormones usually also contain a fungicide to prevent fungi from rotting of the cutting
- You can make your own natural root hormone – Willow Water. Willow water is mild form of root stimulating hormone which contains IBA. Just chop up fresh willow twigs, dump them in boiling water, let it cool overnight, and then let the stems of your cuttings stand in the water for a few hours to soak it up, before you pot them up.
|Step 5 – Prepare propagating medium and insert cutting
Fill a pot with propagating medium and water the propagating medium to moisten it.
- Any medium which will lend physical support, provide moisture and oxygen in the right balance, is low in fertility and is free of pathogens can be used for propagating cuttings
- The propagating medium needs to be well-draining to provide sufficient aeration to grow roots. If it is anaerobic (no air), the roots will rot. Only a few plants will grow roots if the cuttings are placed in a container of water. It should also retain enough moisture so that watering does not have to be done too often. It doesn’t need to have high fertility or any nutrients, because the cuttings don’t have roots to be able to use them.
- Materials commonly used as propagating medium are coarse sand, regular potting mix, coconut coir, or blends such as a mixture of one part peat and one part Perlite (by volume), or one part peat and one part sand (by volume).
Insert one-third to one-half of the length of the cutting into the propagating medium. Keep the cuttings vertical and space cuttings far enough apart from each other so they don’t shade each other out so that all their leaves can receive light.
Step 6 – Add more cuttings if propagating
Since cuttings don’t always “strike” (grow roots), it’s best to add a few cuttings into your propagating medium to increase the chances of success.
- Even with plants that have really low striking rates, say as low as 20%. then if you put 10 cuttings in, you’ll potentially get 2 that take root.
Step 7 – Label the cuttings to identify them
I can’t overemphasise the importance of labelling plants when propagating by seeds or cuttings.
You might think you know what the plants are when you’re preparing them, but if the cuttings take a few months to grow roots, and you prepare cuttings of other plants, what are the chances of telling them apart?
Step 8 – Cover the cuttings to retain moisture
Set the cuttings in a bright, warm location, away from direct sunlight
In order for cuttings to survive, they need to retain moisture inside of them. This is because the leaves can lose moisture via evaporation, but there aren’t any roots to take up more water to replace what is lost from the leaves.
The way to keep the cuttings alive is to maintain the humidity (moisture in the air) around them, while at the same time not keeping them to damp, otherwise they will rot and go mouldy!
To do this we lightly water the cuttings again. Then cover the cuttings with some kind of clear plastic that will hold the moisture in and then place the cuttings in indirect light, .
- Avoid direct sun, otherwise the cuttings will overheat and cook in their airtight enclosures!
- Keep the medium moist until the cuttings have rooted.
Shown below is a propagating pot, the top “butterfly” can be twisted to expose the air holes in the lid to let air in when the cuttings start growing, to allow them to adjust to lower levels of humidity and “harden off”. This pot is part of a “Aquamiser” Propagation and Seed Raising kit.
You can also put regular pots of a smaller size into a plastic propagation tray, these sell for a few dollars and last a while, available at most nurseries and garden stores. Note the green air vent “butterfly” on the top of the lid. This also lets you open up the vents holes in the lid to let the heat out if it gets too warm, or when the cuttings start growing and need more air flow.
|Here are a few other possibilities. Here, I’ve used a regular plastic drink bottle cut in half, and pushed it slight;y into the propagating mix into the pots so it holds and seals the moist air in. The tops work better as you have a lid that you can open. I’ve put them next to the Aquamiser pot for comparison.
Incidentally, you can accommodate taller cuttings simply by cutting the bottom of the plastic bottle off only, leaving a taller humidity cover. They also work in the garden to protect seedlings from snails, just remember to take the lid off if you use them in the garden in direct sunlight!
Step 9 – Cuttings have rooted when they show new growth
The time taken for cuttings to “strike” (produce roots) varies, it depends on the type of plant, and the environmental conditions – heat, light, season. Some plants root readily while others can take what seems like forever. If the cutting still looks alive, be patient!
Newly rooted cuttings should not be transplanted directly
into the garden. They need some time to adapt and “harden off”.
Transplant them into larger pots, and provide them with some nutrients. Avoid the urge to overfeed them, fertilize them lightly. Their roots are still quite delicate.
By growing the new plants to a larger size, you help them establish a stronger root system, which makes them much more resilient, and increases their chances of survival when you finally transplant them to their permanent location.