Xerophytes may be trees and shrubs, perennials, annuals, grasses, or bulbs. Groundcovers, a common substitute for lawns, may be in the form of herbaceous perennials, ornamental grasses, or deciduous or coniferous shrubs. Drought resistance is the capacity of a plant to withstand periods of dryness. Water from the soil enters the plant through the tiny root hairs at the end of the roots. Some drought-resistant plants have extensive root systems with a large active surface area which is capable of rapid growth into the deeper subsoil strata where moisture may be available.
Native grasses are also very deep rooted.
Alternatively, some of these plants have shallow, fibrous roots systems which simply act as a sponge, immediate absorbing any rainfall which might fall on the soil surface. Water loss from the surface of the plant through transpiration may also be reduced. The stomata are the openings in the epidermal layer of the leaves through which water leaves the plant in the process of evaporation called transpiration. In drought-resistant plants the stomata may be sunk deep into the epidermal layer or be of a smaller size, thus reducing water loss. These plants may also have mechanisms for triggering early closure of the stomata.