Etiolation

Etiolation is characterized by reduced girth of tip growth. In advanced cases abnormal stretching, thinning, and weakening of new growth can be observed. In extreme cases the epidermis in the affected area typically becomes pale green, yellowish-green, or even white. Rib count may appear compressed or reduced, and areoles show stunted development with significantly shorter, weaker, or absent spines. If the plant is not vertical, the growth often forms a “hook” shape upward as the plant stretches in search of light.

Etiolation is a universal physiological response observed globally in cultivation when plants are exposed to inadequate lighting combined with active growth. Alternatively, etiolation can sometimes be observed in rooting cuttings due to the plant being unable to uptake enough water and nutrients to keep up with requirements of new growth.

• Light & Acclimation: Stretched plants require increased light, but must be transitioned slowly to avoid sunburn.
• Nutrient Balance: High levels of nitrate nitrogen relative to available light trigger etiolation.
• Dormancy & Airflow: Ensure cacti enter proper dormancy during winter by withholding water and lowering temperatures. Stale indoor air and high humidity prevent proper dormancy and encourage etiolated growth. Minor softening or deflation is normal during dormancy, but squishiness accompanied by black marks indicates rot or severe stress. For more information see dormancy
• Propagation & Salvage: Etiolated tissue remains a permanent structural weak spot. To salvage the plant, cut the tip off using a clean knife sterilized with isopropyl alcohol after increasing light. The stump will produce new pups, and the cut tip can be calloused and rooted in dappled shade. If the skin breaks easily when rubbed, the plant is rotting and requires immediate excision of the decayed parts.
• Prevention in cuttings: To prevent etiolation in cuttings, best practice is to cut as large of pieces as possible and provide conditions for roots to form as quickly as possible. Larger cuts will contain more stored energy and will be able to sustain full girth growth for longer while unrooted. Applying rooting hormone to the bottom end of fresh cuts and providing warm tempuratures will increase rooting speed.