Q. Our cactus has started to die from the top down. We lost our first one in May, before the summer heat even started.  Do you have any idea why this is happening?  We were watering, with bubblers, three times a week, for about 5 minutes. We increased that when they started to die, but it did no good. Any information will be appreciated.  Readers cactus dead or with severe damage A. Wow, judging from the pictures you do have a problem. The plant looks dead from top to bottom. This looks like one of the Cereus or night-blooming cacti, a pitaya type.             When did you see this happening? This looks very similar to freeze damage from the winter but if you are just seeing this now then of course it is not. Another possibility is root rot if watering too often and not giving it a break of dry soil between waterings.             Three times a week is going to be excessive for this plant and may be the problem. The plant would prefer a large amount of water and then long times between waterings, much like rainfall in dry climates. Another view.             But bottom line the soil needs to dry thoroughly between waterings to prevent root rots. When planting, make sure the soil is amended with some real good stuff at planting. Cacti can survive poor soils better than many plants but also perform better with an enriched environment provided the soil drains water freely and dries between irrigations.