Fast growth is not good. The slower psychedelic cacti the better. The alkaloids you want are deffence mechanism. The harder the conditions the more they produce to cope. Lophophora use mescaline and a pesticide and antifreeze. The more quickly the growth the more water the cells will contain diluting the good stuff. Slow growth in "difficult" conditions need more of the alkaloids to stave off drought, heat or cold. Now im not saying dont water on the contrary plenty of water during the growth period is good but adding fertilisers weekens the growth. Cell take up the nitrogen and use it to build proteins and get bigger quickly. The average size of the plants cells increase so more liquid ie water is needed to fill them. The plants reach a potential of growth that is not limited by the conditions of its natural environment. Waterbabies are not just meat head wrestlers with a passion for anbabolics. Ultimatelly the plant does not need to produce the chemmicals to survive as they are not needed so less are produced.
If you hard grow you cacti they get stronger and therefore make stronger concentrations of protective alkaloids. Use mineral soils, most psychadelic cacti can growth in the cracks between bare rock with no actual dirt in their natural settings. My soil mixes and a combination of stones, rocks, grit, clay no ingredients from plant or animal sources. Keep the soil very free draining so in the summer you can water every day if needed, the cacti should only be watered when all the soil is dry even inside the bottom of the pot. The choice of rocks to make the soil will eliminate the need for fertilizers that add potassium and phosphorus. Granites, limstone, dolomite, schists, sandstones, and various volcanic pumice and lavas will contain the required mineral nutrients the plants need. The roots have symbiotic bateria that disolve the dry rocks with enzymes the resulting salts are shared with the plant in exchange of a living environment. Cacti need winter rest periods. Normally in their natural environment they will have periods of drought such as a dry winter then wetter periods in summer is common. The cacti need this rest period for health and strong gowth but this period also results in increased alkaloid content as a side effect. Watering should stop during winter cacti can go for months without water in the mexican desert heat so a cool to cold higher latitude winters are surprisingly easy for the plant but thete is a draw back, damp, this causes rot. Not good. So if the plant is kept completely dry from November till march thats fine. It will stop any risk of rot and during this time the plant will use the reserves of water. Over the corse of the drought period the physical appearance of the plant will change, it will essentially deflate inceasing its alkaloids concentration. The best time to harvest is at the end of the drought period before the first watering. If you intend to then grow new heads on the remaining tap root or not ready to harvest be carefull until the plant is ready. As I mentioned earlier the symbiotic bateria dissolve the dry rock. The bateria don't stop doing this just because the plant is sleeping. Salts build up in the roots so the first watering causes a lot of swelling which can cause the plant to split. This is a doubled edged sword as it makes the plant more susceptible to infections from fungi and bateria causing rot. The plant will also up alkaliod production to defend its self. Water slowly to begin with, start when the first good sun in spring shines as early as February subject to night time tems. Dont water if night time temperature gets lower than say 5°C this early in the year. As the day light hours increase the soil should dry quicker allowing more waterings. Water in the evening so plants are dry by the time morning sun gets to them. In autum reduce frequency of watering with the temperture and stop well before the first frosts if you get them. Keep plants in bright direct light all year in higher latitudes, use shade cloth to reduce the light in lower latitudes or if the plants show too much reddish colour changes. You will get slow growth following this method but its stronger healthier and thetefore more productive growth
Trichocereus growth while similar is a little more forgiving. They require somewhat richer soils so along with the mineral ingredients add good quality loamy soil to about a 1/3 of the soil mix. These plants also will cope with damper conditions so dont be affraid to water a lot regularly in the growing season. While they will grow quickly in strong sun apparently the alkaliod content inceases when it struggles to find light so before you are ready to harvest put in the shade until it aquires a much darker appearance.
Happy growing
