Hydrangeas represent a genus of around 75 species (as well as many hybrids and cultivars) of flowering plants native to both Asia and the Americas. They can be either deciduous or evergreen, but the most commonly cultivated temperate species all lose their leaves in the Fall. Most hydrangeas are shrubs or small trees between 1–3 meters (3–10 feet) tall, others are woody vines that can climb up to 30 meters (98 feet) high. The flowers of most species are white, but some (notably H. macrophylla) can have blue, red, pink, light or dark purple flowers; the colour of the flower is affected by the availability of aluminium ions in the soil, which is determined by soil pH. The plant’s floral display consists mostly of sterile florets grouped into large clusters. Hydrangeas are not drought tolerant and, in general, require at least 3 centimetres (1 inch) of water per week; they grow best in consistently moist, well-drained soil with a moderate nutrient level.