Yellow Tips on Senita Cactus

Background

• Pachycereus schottii are native to the rocky hillsides and wash border of the Arizona desert, according to the University of Arizona. It is a tall, upright cactus that grows to 15 feet tall with many column-like stems. Each stem has five to 10 rib sections. The upper areas of the stems have bristles called areoles, 1 to 4 inches in length, while the lower portions of the stems have shorter spines. The pale pink, 1 1/2-inch cactus flowers bloom from April to August only at night. The Senita's botanical name comes from Arthur Schott, who was a plant collector for the Mexico Boundary Commission.

Care

• The Senita cactus can grow well in a home garden. The plant does not like cold temperatures and should be planted in a partially shaded area where it will have sun only in the coolest times of day, such as early morning and evening. The cactus can be kept indoors if the outside temperatures drop lower than 59 degrees Fahrenheit. Water the plant only every four to five days when the soil is dry and use only one to two glasses of water. During the winter, water the Senita even less.

Yellowing

• One of the biggest problems with growing cacti is when you place the plants in an environment that is different than their natural habitat. The Senita is prone to aphids and fungus problems, which can cause yellowing. Overwatering and not watering enough can also turn tips yellow. Unexpected extreme high or cold temperatures create yellowing as well. Other causes of yellowing include too much sun, moving a cactus to a new location and using the wrong fertilizers. Also, physical damage to the cactus will cause it to yellow.

Solutions

• Yellowing is the first sign of problems or stress for the Senita before it turns brown and dies. Examine the Senita's environment. If you just planted it, it may take time to adjust to its new surroundings. Give it succulent fertilizer, which is rich in potassium and low in nitrogen. Only water the cactus when the ground is completely dry. Be sure to give the cactus good drainage because standing water is bad for it. If it is living outside during a cold spell, place a cotton sheet over it or shine a 60-watt light bulb nearby. If it has too much sun, change its location. Fungus problems look yellow but have patches of dark brown or black. It may be receiving too much water. If you find this, remove the section or use fungicide. Bug infestations can produce small yellow spots; try spraying a succulent insecticide.