Complex sentence: They should be planted to the original growing depth and, as with cacti, in their original directional orientation: the original south side of the plant, which has become more heat-and sunlight-resistant, should again face the brighter, hotter southern direction.
Split into simpler sentences: They should be planted to the original growing depth and, as with cacti, in their original directional orientation. The original south side of the plant, which has become more heat and sunlight-resistant, should again face the brighter, hotter southern direction.