Saguaro

Saguaro (Carnegiea gigantea) grows best when its natural cycle of strong light, freely draining soil and measured watering is respected. Give it full, intense sun. indoors, the brightest south-facing window available. Water it according to its seasonal needs: soak deeply, then allow soil to dry completely. almost none in winter. Plant it in coarse mineral mix — pumice, decomposed granite and a little loam. A container with an unobstructed drainage hole is essential, because moisture lingering around cactus roots can quickly lead to rot. Keep its temperature needs in mind: tolerates 5–40°c. brief frost survivable; prolonged cold is fatal. During active growth, check the compost before watering rather than following a rigid calendar, since heat, light and pot size all change how quickly it dries. Reduce watering during cool or dormant periods, keep the plant well ventilated, and wait until the growing medium is dry before watering again.

From seed — exceptionally slow. A one-year seedling is the size of a pea. Sow fresh seed on the surface of a fine, sterile cactus mix and keep it warm, lightly humid and out of harsh direct sun until germination. Once seedlings are established, increase ventilation gradually and allow longer intervals between watering to reduce the risk of damping off. Young cacti are especially vulnerable to excess moisture. Use a small pot with excellent drainage, provide bright filtered light while roots establish, and move the new plant gradually into the light, temperature and watering conditions preferred by a mature Saguaro.