Because I live in the subtropics, I am lucky enough to be able to strike many cuttings and get many species to grow from seed just using garden soil or potting mix as a medium. Unfortunately not every one is as lucky.
Many people struggle to get cuttings to take, or grow seedlings because of fungi and bacterial infections. So extra care and attention in hygiene matters are needed to get them to succeed. So to make your own propagation mix for striking cuttings or to grow seedlings, without spending a fortune.
Compost / and or potting mix,
River sand or a coarse landscaping sand. (Beach sand is not real good because of the salt content, and the grains are usually too fine). (All would have to be soaked / rinsed before using anyway).
Perlite / vermiculite / polystyrene beads (optional for extra moisture retention and openness of mix)
Fine Gravel (optional for well drained mixes)
A sieve of some sort. (This can be a proper garden seive, a kitchen seive, a colander, a grater or even a garden pot allowing the action of seiving through the holes in the bottom, or even just your own hands cupped together seiving the compost through your fingers. )
Bleach (1 / 10mix) or Methylated Spirits (1/10) or Vinegar (1/3) or hot soapy water, (Sterilizing Agent)
Boiled or distilled / demineralized water
Oven. (If heat sterilizing)
Old roasting or baking tray for the oven. (If heat sterilizing)
Sterile container to store excess finished mix in.
Ensure that your hands are clean and sterile before beginning. Gloves can be used because of issues of handling soil and other products which are possible carriers of Legionella longbeachae a pneumonia type of disease. This is a naturally occurring bacterium that is a normal part of the environment.
Secateurs / scissors / knives and work spaces and storage containers should be sterilized with a diluted mix of bleach or vinegar or methylated spirits and water.
First you need to sieve out a quantity of fines from some well matured compost or potting mix. (Or cheat and use coir peat instead). Mix this with about – – 1/3 clean sand.
If you are preparing to grow things that require well drained soil eg pineapples, cacti, etc., as plants then think about adding a bit of fine gravel to your propagation mix. To improve drainage even more. You can even add things like perlite and / or vermiculite and / or polystyrene beads when ready to pot up cuttings. This would improve moisture retention in the propagation mix. These will also improve air circulation around the bases of the cuttings.
To kill germs and bacteria in the mix you will have to sterilize get the soil / sand / gravel mix so that you kill most or all harmful bacteria and fungi.
Possible ways of treating the propagation mix, include.
Soaking Treatment – soaking or rinsing the mix in the dilute sterilizing mix mentioned above, (except the soapy water option), then soaking and or rinsing it after in boiled or distilled water. Sun / air dry any excess mix to insure that no problems grow before you get to use it again.
Temperature Treatment – laying the mix on a tray in an oven for the 30 minutes or so needed to raise and maintain a temp 'of over 60 degrees celcius. If you put the mix in thick in the trays, then the temp at the core of the mix is what you need to be concerned about. Not just on the surface of the mix. This then needs to be cooled completely before using.
So if you do not want to run the oven specifically just for the propagating mix, then have it ready to insert after using the oven for some normal cooking or baking, while it is cooling down.
Mix which has been heat treated to be sterilized may need to be soaked before using with cuttings as it may be water repellent at first and deprive new cutting of moisture till it reacquires the ability to hold and store water.
If you have made up excess propagation mix it can be stored in a sterile container until needed in the future.
When planting up cuttings ensure that the pots, labels, and even the stick you will be using to poke holes in the mix has been washed or soaked in a sterilizing mix before using them.
It also does not hurt to give the cuttings a quick rinse in the sterilizing agent, 9except the soapy water option), and then a rinse off with the sterile water as well.
When watering cuttings you can improve the success rate by watering the cutting for a while with sterilized / demineralized / boiled water. At least until the cuttings show signs of starting root germination.
Also remember that there is little or no fertilizer content in your mix, so a fertilizing program will have to be maintained at about pl plant strength to allow the new plants to have the nutrients that need to start and maintain root and stem / leaf growth.
Most cuttings strike better in a bright shaded environment.
You can also improve the opportunities of the cuttings taking by keeping the cuttings in an environment away from the general plants in your garden, greenhouse or shade house.
Now while it is expensive to have a dedicated greenhouse just for propagation. It is not difficult to ensure that a small separate incubator can be put aside. Even if this is only something like a throwaway plastic cake / sandwich container, or a clear cd storage tower that blank cd / dvd's come in.
Or even just a plastic shopping / kitchen / bread bag thrown over the container, and kept up off the cuttings with chopsticks, sticks, skewers or straws, etc. And then sealed around the cuttings.
This also helps keep them away from pests and blown in fungi and bacterial attacks while they are establishing. Though once you see signs of them getting established you will need to start opening up the incubator to harden off the new plants.