Starting Trichocereus cactus from seed is extremely simple- here is a basic outline of what you'll need to do:
- Acquire a container which has a transparent lid or use plastic wrap to cover your seed container. I personally like to use whatever I have laying around. Clear 5.5 oz portion cups with the snap lids are a great option. These are similar to the ones that you may see at a restaurant that uses them as small to go containers for salsa and may be found at an economical price at most stores or online.
2. Fill your container about a quarter to a third of the way up with sifted soil- we take Fox Farms Happy Frog and use a collander to separate the larger chunks. You can use any basic gardening soil available to you- just be sure to try and sift out the bigger pieces of bark and other materials which can cause some seeds to not make it. For example, if a seed lands on a piece of bark and it germinates, its early roots may be unable to reach the soil and subsequently die.
*Note: depending on your environment, your soil may require higher drainage capabilities. In order to compensate for this, consider adding pumice or perlite to your mix to ensure it can breath. Trichocereus are extremely fast growers relative to your classic "desert" cactus. The more you're able to water and fertilize them, the faster they will grow. Having muddy soil slows their growth and can induce rot. Make sure you soil can drain easily so the roots can breath.
3. Spritz the soil surface with water- this will help the seeds from bouncing around when you sprinkle them in the container. Give the seeds another spritz after sprinkling- there should be enough moisture in the container that it creates a humid environment, a miniature greenhouse, once the lid is sealed. The soil should be damp but not overly- there should be enough moisture in the container that a small amount of condensation forms on the lid. Keep an eye on moisture level to ensure mold and rot do not take hold. This is less of an issue later when the cactus are more established and the conditions are not super wet most of the time.
4. Place the sealed container in a protected area- on a window sill, porch, inside under a basic light- nothing fancy is required to germinate them. As the seeds mature, they will appreciate more light. They can be left in the container for a few months. As they get to this point, you may choose to remove the lid and either transplant them to separate containers carefully or drill holes. Once the lid is removed, they will need watering more often. Again, Trichocereus are heavy feeders compared to other cacti so don't be scared to fertilize them. I personally like to use Botanicare and Cal-Mag.
*Note: sterilizing the soil is optional. I've had great success without sterilizing the soil, however you may experience otherwise depending on the situation and soil composition. I have had lost a couple of cactus however in my approach I like to let nature take its course and weed out the weaker genetics for my particular region.
*Note: Make sure your soil doesn't dry out while waiting for the seeds to sprout. most should germinate within the first couple weeks. If they don't pop up immediately, don't give up on them. Remember, a fluctuation of temperature and moisture level can actually encourage some stubborn seeds to sprout. To help with this, you can use a heating mat in colder climates and during the winter in warmer climates in conjunction with turning on your lights/the cycle of the sun. Turn on the mat/lights in the morning and both off at night.
*Note: If the seedlings start turning red, its likely they are receiving too much light- wane the light down until they recover the green color. It will not stunt the plant indefinitely but may take some time to bounce back from being burned. Burning can happen very fast and its important during these early stages of seeding development to keep an eye on light levels and acclimate them appropriately to higher level of light.
*Note: artificial lights are never a replacement for the sun. While seedlings may pop up under lights and seem to grow okay, their growth rate will increase exponentially and you will see less etiolation (stretching) once growing in real sunlight. It doesn't have to be full sun, this is a balancing act- while some Trichocereus will handle full sun just fine, others may be more sensative. To bring out any potential "blue hues" a certain phenotype may be capable of, try dappled shade. Not full sun, not full shade- dappled.