Growing Living Stones at 63rd Parallel North

during october i water and fertilize my living stones every 10 days: on the 6th, the 16th and on the 26th. at the beginning of the month i still find webbing on the monilaria plants so i also spray with the diy miticide on the 6th and on the 16th. i reduce the daylight hours gradually untill the plant lamps are on only 12 hours a day. i am aiming at 8 hours at winter solstice and at 16 hours at summer solstice but i began to wonder if one is too little and the other too much. i read about the 34th parallel south (about the parallel of cape town) because i believe that the southern tip of africa has the most extreme light levels the living stones could possibly encounter in their habitat. well, their habitat is actually a bit more north from there in the namib desert but i think it's close enough for an approximation of the most extreme light levels. at the 34th parallel south the sun is visible for 14 hours, 28 minutes during the summer solstice (in december) and 9 hours, 50 ...

this month i continued gradually lenghtening the photoperiod (daylenght) with my plant lamps. at the end of the month i had my plant lamps on for 12 h/day. during this month i discovered that the monilaria plants were beginning to grow very strongly towards the light source and that one of the argyroderma plants had also begun changing its leaves the second time. i bottom watered and fertilized my living stones on the 6th, the 16th (one conophytum plant was wrinkled), the 22nd and on the 29th of march. a new monilaria leaf tip turned bright red after bursting into light.

this month i discovered that the 2 lithops plants with brand new leaves had etiolated. it means they had received too little light (8 h/day) and i began gradually lenghtening the photoperiod (daylenght) with my plant lamps. at the end of the month i had my plant lamps on for 10 h/day. i bottom watered and fertilized my living stones on the 2nd, the 7th (i didn't fertilize), the 11th, the 17th, the 22nd and on the 28th of february. the 2 etiolated lithops plants on the 7th of february the last lithops plant is finally splitting

Wikipedia on grow lights :  "A plant's specific needs determine which lighting is most appropriate for optimum growth. If a plant does not get enough light, it will not grow, regardless of other conditions." "Grow lights usage is dependent on the plant's phase of growth. Generally speaking, during the seedling/clone phase, plants should receive 16+ hours on, 8- hours off. The vegetative phase typically requires 18 hours on, and 6 hours off. During the final, flower stage of growth, keeping grow lights on for 12 hours on and 12 hours off is recommended." "In addition, many plants also require both dark and light periods, an effect known as photoperiodism, to trigger flowering. Therefore, lights may be turned on or off at set times. The optimum photo/dark period ratio depends on the species and variety of plant, as some prefer long days and short nights and others prefer the opposite or intermediate "day lengths"." ...