Tropical savannas, sometimes called tropical grasslands, are rolling grasslands with scattered trees and shrubs. They lie between tropical rain forests and deserts in parts of Africa, Asia and South America. They are warm areas with distinct dry and wet seasons. The dry season, usually with at most 4 inches of precipitation, is usually winter. The wet season is usually summer. The specific plants that grow in tropical savannas will differ, depending on the savanna's location.
Many savannas, especially those in East Africa, host different varieties of acacia trees. Northern Australia also hosts acacias. Many acacias have thorny branches and trunks. Most have complex, fern-like leaves made up of a series of smaller leaflets on stems. Local products often use acacia wood. A common ingredient in many foods, gum Arabic, is also called gum acacia. Gum acacia is the sap of the acacia Senegal tree. Acacias often have, according to the people who live around them, medicinal properties. Because they sometimes grow in areas where malaria is common, acacias are sometimes called the fever tree. Even though acacias are native to tropical savannas, many grow well in the United States. Some acacias are cold hardy down to USDA Hardiness Zone 9 and above. They need full sun and soils that drain very well. They don't need much water, but deep watering in the summer can help to mimic native growing conditions.
Eucalyptus is native to Australian tropical savannas. Depending on the variety, eucalyptus can grow from 4 feet tall to more than 150 feet tall. They can range from thin, wispy trees to tall, trees with a narrow silhouette. Some varieties of eucalyptus can tolerate freezing temperatures and are hardy down to USDA Hardiness Zone 7b. Most eucalyptus do best in full sun, but some may do well in partial sun. Eucalyptus requires well-drained soil. However, some varieties tolerate standing water for short periods of time. It is also drought tolerant and may only need water in the summer.
Tropical savannas have many different kinds of grass. Grasses adapted to tropical savannas have very long taproots that reach deep beneath the soil. This allows the grasses to find water during the dry season. Some grasses drop their leaves in the winter to conserve water. Some grasses have evolved to discourage consumption by animals on tropical savannas. Some have very sharp edges and others are bitter. However, most grasses are food for one or more animals on the savanna. Varieties like Miscanthus purpurascens are commonly grown as ornamental grasses in North America. Although a savanna grass, this variety will survive down to USDA Hardiness Zone 4. It needs full sun and can grow in poor soils, as long as they drain well.
Grasses that originated in tropical savannas include Bermuda grass, which originated in African savannas. Bermuda grass can grow as tall as 1 1/4 feet and has roots that can grow to 59 inches deep. Elephant grass is another African savanna grass. It can grow to 10 feet tall with 2 to 3 foot long leaves.