Cacti cuttings
From azo.dk
The fastest and most popular way of propagating cacti.
Contrary to propagation by seed, which not only takes years for some of the slower growing species, but also require special equipment - not to mention constant care - cuttings can be rooted within weeks. When the cutting is rooted, it can almost immidiately be treated as an adult cactus.
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Tips to avoid problems
The primary reasons for unsuccessful rooting af a cutting is rot, mould and fungus. Forunately, there are several methods that will decrease the risk of loosing the cutting.
Soil sterilization
Sterilizing the soil by heating is quite effective killing bacteria, mold and fungus, but definitely not 100% effecive.
Anti fungus chemicals
Using anti-fungus chemicals in the water, or by spraying inhibits fungus and mould growth. Together with soil-sterilization it is quite effective.
Soil hydration
If the soil is soaking wet, or even just wet, the chance is much higher, that bacteria will be able to attack the cutting and destroy it. Lightly moist soil is quite enough to persuade the cutting to develope roots. When a cutting is damaged by rot, it's unlikely that it will recover. Mold and fungus on the other hand, is easier to treat with anti-fungus chemicals. But of course - the best approach is to prevent fungus and mold in the first place
Air humidity
High humidity prevents water-loss, and keeps the cutting hydrated in the weeks before it developes roots. The downside is, that high humidity is a perfect invironment for fungus and mold.
How to root a cutting - my way
In order to successfully root a cutting it must of course first be severed from the mother plant. With opuntias, you can often just twist of a segment. Otherwise, use a sterilized sharp knife. We don't want any bacteria or fungus into the fresh wound.
I've been using this method described below in details for 6 plants, 4 cacti, 1 succulent and 1 houseplant. Every time successfully so far. The longest rooting period vas about 6 weeks, and during this time no fungi or mold developed.
Healing
When severed from the mother plant, the wound has to heal before rooting. If not, there is a much greater risk of infection. The prefered length of time depends of the size of the cutting. For small, lets say opuntia size cuttings, 1 week should be sufficient. Larger columnar cuttings should rest for a few weeks before rooting attempt. Generally, when the wound is healed and dry, rooting can be done quite successfully.
Prepare the soil mix
When the cutting is ready for planting, you have to choose some kind of soil. I prefer to use regular potting soil, with some fine sand, and some coarse sand, in quantities of about 2:1:1. I use this mix because the ingredients are cheap and easy to find. The goal is to produce a mix that is pretty loose and not too chuncky. So be sure to remove all the larger pieces from the potting soil. We want the cutting to be in good contact with the moist soil.
Sterilizing the soil
When you have your soil mix ready, you should sterilize it by heating. This step is more essential than most people recognize. The soil is full of bacteria and fungi, which can destroy your precious cutting.
- Moisten the soil mix so it feels just moist.
- Put it into a thin disposable plastic bag and tie a knob. Make sure the plastic can tollerate about 100C.
- Heat your oven to 80-90C and put the bag into the oven.
- Let it sterilize for 2 hours or more.
- Let the soil cool down to room temperature before using.
The plastic bag prevents the soil from drying out, and keeps most of the unpleasent odours inside. Sterilizing longer than 2 hours could probably be beneficial. The low temperature is not chosen randomly. Higher temperatures could chemically alter the composition of the soil, which we do not want.
The soil is not completely sterile after this treatment. Complete sterilization requires a higher temperture. But I've had no problems with fungus or rot by using this method so far.
Planting
Choose a pot just large enough for the cutting. It's just going to be the cuttings home until it is rooted successfully, and started to grow. Large pots with more soil than required could potentially increase the chance of mould of fungus to develope.
Generally, the cutting should not be burried deeper as needed. For opuntia type, just a centimeter or two is quite enough. Small cuttings of mammillaria for example, should be placed on top of the soil. Just make sure it has good contact with the soil. Larger columnar cutting should be supported in some way, and only planted as deep as needed. I've never done any large columnar rooting, so I've got no experince with this kind.
Planting the cuttings on top of the soil (if possible) also makes it exceptionally easy to determine rooting status.
Rooting dome
I prefer to place my cuttings under a dome for the following reasons.
- No need to water during the rooting period
- No drying out
The dome can be anything from a plastic bag to a prefessional cutting-box. I don't think it makes any difference. I use some CD/DVD cakeboxes. You should not open the dome during the rooting period more than neccesary. Once a week you should check the rooting progress by twisting of pulling the cutting lightly.
Determine successfull rooting
If you place the cutting as loose as possible on top of the soil, then it's overly easy to determine if rooting has taken place, and how strong.
- Simple twist or pull the cutting very lightly. If the resistance is greater than when the cutting was places in the ground, you can be sure that rooting has taken place.
- Does the cutting look a little dry, or is it a little softer than at the time when it was cut. Then the root-system is probably not big enough yet. Keep it out of direct sunlight, until rooting is sufficient.
- New growth is an almost 100% sure sign of rooting. Look at the picture of the Mammillaria crinita cutting at the top of this page. Growth can be seen at the top, and it has started to produce shoots too ...
