Most plant roots die back quickly when you leave them exposed to drying air and sunlight; they only thrive in moist, nutrient-rich soil. Succulents, such as cactus species (Cactaceae), hardy in U.S. Department of Agriculture plant hardiness zones 5 and higher, actually sustain healthy roots if they are pulled from the ground. These roots can be exposed for a few days to several weeks if they are properly prepared for a temporary soilless environment.
Unique Succulent Traits
Roots absorb water, nutrients and oxygen from the soil and into plants' vascular systems. Because many succulent species live in extremely hot regions, they developed a water-storage technique to survive extended droughts. Stems and leaves act as water balloons; they visibly swell during rainy periods to store as much moisture as possible. Succulents steadily contract as they use the stored water for normal photosynthesis and growth. If their roots are exposed for an extended period, the succulents rely on stored moisture for continual health, rather than depending on constant soil moisture.
Root Dryness and Calluses
If you remove your succulent from the ground -- for example, during a landscaping project -- keep the roots as dry as possible. Dryness causes the succulent to revert to a dormant state. The plant then directs energy into basic survival and siphons moisture from within the stems and leaves for suspended life. Succulents continue to photosynthesize with their stems and leaves, whether they are in soil or not. In fact, you can propagate most succulents with cuttings that rely on exposure to root effectively. For example, a leaf removed from a mother plant must sit out in a dry area for approximately 14 days to allow the injured area to callous, or harden. You may need to leave it exposed longer if the cut is large or surrounding air is too humid. Roots grow quickly from the calloused area once you plant it in new medium.
Roots exposed for several weeks are stimulated by repotting. Use a mixture of 1 part sand, 1 part peat moss and 1 part loam, and do not moisten it initially. Whether you are transplanting an existing succulent or propagating a new cutting, roots and calloused leaves cannot sustain moist conditions yet. The roots are not actively absorbing water and will effectively rot in the new environment. Sunlight and air are key components to induce root activity. Choose a bright, indoor area without direct sunlight for your repotted succulent. Roots placed into the medium need time to heal any transplanting damage. After seven days, water your succulent sparingly to start root absorption.
After root exposure and repotting, your succulent benefits from mild temperatures between 64 and 75 degrees Fahrenheit. This temperature range provides warmth for increased root and photosynthesis activity after exposure. After the first week, water the succulent weekly to keep soil moisture consistent. Your succulent will quickly acclimate to its new medium, producing new roots and extending current ones into the soil for healthy stem and leaf growth.
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