What Causes a Cactus to Go Mushy at the Bottom?

Cactus Irrigation

• Most types of cacti, besides Christmas cacti and other rainforest cacti, require infrequent waterings. The University of Minnesota Extension recommends watering cacti just enough to keep them from shriveling. If an under-watered cactus begins to shrivel, it will become somewhat mushier without its supply of water inside to plump it up. At the same time, over-watering leads to cactus rot diseases, which can cause a cactus to go mushy at the bottom.

Cactus Environment

• Cacti grow best in warm temperatures and soil that drains water quickly. Their roots do not respond well to sitting in water. If a cactus begins to go mushy at the bottom, it might be rotting internally and beneath the soil due to poor soil drainage.

Root and Stem Rot

• Over-watering and poor soil drainage create the perfect environment for the fungi that cause root and stem rot to grow. Plants with stem rot appear water-soaked around their bases, then they become mushy as the tissue starts to rot. In later stages of rot diseases, the cactus will also get a reddish-brown coloring in rotting areas.

Pythium Rot

• Pythium rot is a disease that causes a cactus to rot from the inside out, becoming soft and mushy This disease especially tends to attack cacti at their roots and crowns. Plants get this disease when gardeners over-water them or plant them too deeply in the soil. Avoid wounding cacti to prevent open areas where the fungal spores can enter the plant. Proper irrigation and soil drainage should also prevent most pythium rot from causing a cactus to go mushy near the base.