Mexican Fence Post Cactus Turning Black

An extremely variable species is showing typical etiolated weakened growth due to poor light levels and probable overwatering in such a situation.

Mexican fence post cactus turning black. The most common reason for this is being too wet and worse root rot. There may be no way to save it usually by the time you see the symptoms the cactus will be fully involved. This is when you see yellowing from the bottom of the plant that soon spreads to the top. You will notice the plant becoming soft and mushy when touched.

Dry rot is common on prickly pear pads appearing like large black eyes with brown rims. This mexican fence post cactus grows surprisingly fast and has new red spines. However you might try cutting out the diseased plant parts by digging into the cactus with a sharp knife and cutting away the damaged tissue. The mexican post is turning yellow on one side and the barrel cactus has lines on one area.

In spring the cactus produces tubular pinkish red flowers that are very showy. The mexican fence post also. The tall stems branch out from the cactus base to form a fence like cluster of tall cylindrical posts usually with 5 or 6 pronounced ridges. The mexican fence post in my planter is doing the best.

Small black circular spots develop on the cactus slowly expanding to upwards of 2 inches. I also noted that both these cacti where they have the yellowing or problems are are. Your cactus looks like cereus validus. These are signs of root rot and when this happens it is harder to remedy and save the plant.

I recently bought these 2 cacti and placed them in the same pot. Ironically the mexican fence post in my plant container is growing the fastest and shows no signs of stress from the summer sun. The rest of the barrel cactus ooks fine. The plant s common name is derived from the fact that in many villages and towns of mexico it is used to construct a living fence mainly along roadways.

Along these ridges run symmetrical rows of small white thorns that make the mexican fence post look striped from a distance. Remedy cut off both stems to around 1 below where the blackening starts and leave to dry both roots and cut for several months yes months or until spring returns and leave in a bright moderately warm place. The mexican fence post is one of the most attractive and cleanest looking cacti available. Photo by doug martin.