To grow a cactus, determine the type of cactus to create optimal growing conditions. Forest or jungle cacti absorb moisture and nutrients from the air and the organic content of the forest. Replicate these conditions with the proper soil mixture and good drainage. Water forest cacti once a week. Full sun in the morning and shade in the afternoon ensures healthy blooms. Desert cacti require well-drained, rocky soil with lots of nutrients, full sun and weekly watering.
Determine when a cactus needs water by checking the upper 2 inches of soil for dryness. Never re-water if the soil is moist. Seasonal climate conditions directly affect cacti water needs. Desert cacti grown in hot, dry areas requite water once a week, but those grown in humid and cooler areas need water every three or four weeks, depending on soil dryness. Forest cacti might need water twice a week when the weather is too hot, but only every other week during raining periods.
Achieve the ideal soil mix by experimenting with a few recommended components to obtain proper soil drainage. Create a mixture of potting soil using sand, rocks, peat and gravel, as well as pumice, perlite or topsoil for desert cacti. Replace pumice with perlite or vermiculite. Peat hardens the soil and prevents water penetration, so use it in moderation. Prepare the soil for forest cacti by mixing potting soil, pumice, perlite, orchid bark, oak leaf mold or coir. Orchid bark and perlite keep the soil loose and well-drained. However, orchid bark eventually breaks down, adding excess nutrients and moisture to the soil that could damage the roots. Use lime-free compost. Re-pot every three years after blooming with a new soil mix, and fertilize with diluted tomato fertilizer.