If dark, large leaved plants are typically thirsty types, small, light coloured or silvery leaves, especially those covered in fine hairs, tend to indicate plants with low water requirement. Staples of many herb gardens, such as lavender and rosemary, fit into this category. Their woody stems and small, pale leaves minimise water loss.
Not all annuals need large amounts of water – there are plenty of drought-tolerant species, such has cosmos, marigold and the Dahlberg daisy.
Many trees fit into the category of plants with low water requirement, needing only to be watered when they are planted and in the early stages of taking root. Citrus trees are all quite drought tolerant, as are some types of palm trees. Once established, they mainly draw water from the natural cycle of the elements.