Cultivating Cacti from Seeds & Cutting
The following is a comprehensive guide that covers all the basics required for growing and maintaining cacti. It should be noted that it focuses mainly on the cultivation of the San Pedro cactus, but can be applied to many other species of cacti as well.
Cacti are part of a larger group of plants called succulents, which are usually found growing in arid climates. Succulents tend to be thick and fleshy in nature, in order to retain the limited water found in these hotter environments. Many species of cacti have evolved to have thick waxy skin, plus they produce spines and bitter alkaloids to protect them from predators and the hot desert sun. Although cacti take a relatively long time to grow, this resilience makes them excellent house plants that require very little day to day care - ideal for the patient psychonaut.
Growing cacti from seeds
The first thing to address when growing cacti from seeds is the growing medium. At this point it is important to note that the ideal growing conditions for cacti are not necessarily the same conditions under which they produce most alkaloids. Cacti produce alkaloids as a reaction to stress, which often comes in the form of water stress, or lack of proper soil. Should you want to grow cacti primarily for the alkaloids, then the ideal growing conditions will not necessarily yield best results.
While any store bought cactus soil will work, the ideal soil is a simple 50/50 mix of rich compost (humus) with perlite for good aeration and drainage. Often, the use of sterilized soil is suggested, however, this comes at the expense of the beneficial bacteria that naturally live in the soil. As a consequence, abundant use of fungicide is necessary during the process. A sterile rooting medium is not needed when you use good compost. If rot or mold problems arise, cover the cacti with a little sand or vermiculite, that should take of it. It is important to ensure that the substrate is airy and has excellent drainage. The use of fungicide should always be the last option.
Next comes the pots. Small 5 x 5 cm ceramic pots are ideal for germinating seedlings, as they allow soil to dry quickly and help prevent root rot. Place a small amount of cotton wool over the drainage hole of the pot, and pull a few strands of the wool through to act as a wick for drawing up the water. Fill the pots with the cactus mix, and place the cactus seed on top. Gently push the seeds down a little way, but do not cover it with soil or grit yet. Covering the seed in a layer of grit or sand is a popular way to stave off algal growth, but ideally should not be done until a later stage.
The next phase is to create a warm and humid environment for the seed to germinate in. Think of a greenhouse climate, which can also be produced in a small propagator. Use a Tupperware container or a plastic storage box to put your pots in. Carefully pour just over half a centimeter of lukewarm water into the bottom of the container so that the pot bottom feeds the soil and seed. Bottom feeding encourages strong root growth and forces the cactus to grow down to find sustenance. It is important that the water put in is tepid/lukewarm – both hot and cold water can kill the seed. In addition to bottomed feeding, when the seeds are initially planted, they should also top watered with a fine mist spray - although this is only required once.
Place the lid on the container and put it in a warm shaded (but not dark) area to begin the germination. Open the container briefly each day to check up on the seeds and allow some air to circulate. While the lid is open, wipe off any excess condensation that you can get to without disturbing the pots. This will help minimise fungi growth as well.
San Pedro seeds should germinate within 14 days or so - they should look like tiny green spheres. Once they have reached that size, gently place a thin layer of fine aquarium gravel or sand over the surface of the soil. This helps protect the established seedlings from fungal growth, as well as helps to retain moisture within the soil. If you ever see clumps of fungus growing on the gravel, you can carefully remove them by hand.
Once the seedlings are established, remove the lid from the container and replace it with a piece of muslin held on with an elastic band. This will allow for more air to circulate, but also help retain some of the humidity within the container.
San Pedro seedlings are much more sensitive to light than their adult counterparts. When they sprout, they should be a deep, dark green. If they are reddish or brown, or ever turn this colour, they are receiving too much light. In that case, putting additional layers of muslin over the top of the container can help solve this. If they turn yellow, then they are not receiving enough light.
Let them grow like this for 5 months or so, keeping an eye on them and continuing to bottom feed water when the level in the container gets low.
After 5 months, the muslin can be removed and the cacti placed on a sunny windowsill away from drafts. At this point you can stop bottom feeding the cacti. With a small watering can, water around the cacti (not on them) twice a week. They should now smoothly progress into adulthood.
Growing San Pedro from cuttings
Growing San Pedro cactus from a cutting is a much more straight forward process than germinating it from a seed. In order to do this, you need to have living specimen on hand.
How to take a cutting
Ensure the cactus being cut is at least 46 cm long from soil level. You basically want to cut the cactus into 3 pieces. Using a sharp and sterilised knife, firstly cut about 1/3 of the way down the cactus from the growing tip. Make a second cut about 1/3 of the way up the cactus from the soil level.
You should be left with 3 sections each at least 15 cm in length. The bottom part that is still rooted can be left to regrow. The middle and the top section with the tip can be used as a cutting. It is possible to root a smaller cutting, however it is not advisable as the chance of success diminishes.
Next, cut a small and shallow nick into the each rib of the cutting at the exposed bottom surface, then place the cutting in a cool and dark place to allow the bottom to harden and become dry to the touch (this can take around 2 weeks). Once the exposed bottom cut is dry to the touch, your cactus cutting is ready for rooting.
How to root a cactus cutting
Take your cutting and dip the cut end in a rooting hormone as per its instructions.
Fill your pot with a cactus soil mix and place the cutting 7 cm into the soil. Additional stabilisation with a wooden stick might be necessary to prevent the pot from tipping. Also, make sure not to root the cactus upside down. The cactus is in the right orientation when the spines are growing downwards.
Place the cactus in a warm shaded place (out of direct sunlight), and put a very small amount of water into the soil – the soil needs to be just slightly moist to allow the bacteria within to live. You are only trying to avoid “bone dry” soil, very little water is needed. If the cactus gets too wet before it has rooted, it will rot.
Do not water the cutting for 2-4 weeks, and when you do, continue to water very lightly.
It is very important that this process is performed in a warm (no less than 20 degrees Celsius) and bright environment (but out of direct sunlight). If this is done in a cool place or an area with little sunlight, then roots will not grow. If you live in a particularly cold climate, it is possible to root a San Pedro cactus indoors on a warm bright windowsill.
After around 4-6 weeks, gently lift the cactus to see if roots are forming. If they are not, re-bury it and leave for another 2 weeks before checking again. It can take months for cuttings to root depending on things such as temperature, light, and a myriad of other factors – patience is key.
If roots have begun to grow, then carefully rebury the cactus and continue to water sparingly. Once the roots have firmly established themselves, you can switch to maintenance care and start watering it more regularly.
Growing tips for maintaining established cacti
Once a San Pedro cactus is fully established, it can tolerate a bit of direct sunlight. However, cacti can and will get sunburn if left in direct sunlight for too long. Established San Pedro cacti will do extremely well on a warm windowsill with at least 4 hours of bright, filtered day light – and the more it can get, the better.
Cacti should be watered when the soil feels dry to the touch. This will usually be around twice a week. Water around the cacti, not on them.
San Pedro should be kept at a daytime temperature above 20 degrees Celsius in order for it to remain active. They will really thrive at temperatures between 25 - 35 degrees Celsius. Night time temperatures should not be allowed to drop below 15 degrees Celsius.
An adult San Pedro cactus will do well with regular feeding and grow with optimal efficiency. Some people like to feed a very small amount of fertiliser when they water their cacti, others will feed a slightly larger amount every 4-6 weeks. Both are fine, as long as the cactus is not over fed. A good nutrient balance for San Pedro cacti is 7-40-6 (nitrogen, phosphorous, potassium). Fertilisers do not have to show exactly this ratio for cacti to thrive, but it is important that the level of nitrogen is proportionally low, as too much nitrogen can quickly cause a nutrient burn in cacti. Another example of a popular fertiliser ratio is 1-7-6.
During the winter months, San Pedro cacti will go dormant, meaning that both their growth and needs for sustenance will drop dramatically. Depending on where you live, and whether you had your cacti outdoors, you will need to consider bring them indoors in order to keep them warm. If placed on a bright windowsill, they will continue to grow slowly. During this dormant phase, they will not require much water and should only be watered enough to prevent them from shriveling – excess water will cause them to rot. Continue to water them when the soil feels dry, but give them less than you normally would when they are active.