Many people visualise the lush rainforests of the tropics with year-round warmth, humidity and rainfall, but such a climate isn't found all over the tropics. Seasonal cycles of wet and dry occur in many lands between 10 and 25 degrees latitude, according to Radford University. In such places, plants go partially to fully dormant in the dry season when sunlight is less intense, temperatures are cool and rainfall scant. Then, as the sunlight intensifies or winds change to pump in humid air, the wet season causes these same plants to burst into growth and flower. Some plant species bloom when dormant in the dry season, such as dendrobium orchids, mountain ebony (Erythrina variegata) and orchid tree (Bauhinia variegata).
Across the southern reaches of Asia, winds manipulate widespread seasonal changes in moisture and temperature. India, southern China and Southeast Asia endure pronounced fluctuations in temperature and rainfall, and native plants adapt accordingly, losing foliage when it's dry and becoming active once warmth and rains replenish soil moisture. Examples of Asian native plants from this climatic region include teak (Tectona grandis), golden bouquet tree (Deplanchea tetraphylla), copper pod (Peltophorum pterocarpum), dendrobium orchids and gingers (Etlingera spp., Alpinia spp., Globba spp.) according to tropical plant expert authors Margaret Barwick and Kirsten Albrecht Llamas. Bamboo expert Ted Meredith comments many species of bamboo native to Asia inhabit regions with wet and dry seasons, with plant growth most intense during the warm wet season months.
Perhaps the best known wet and dry seasonal areas of Africa are the continent's savannahs, plains areas where many grasses grow amid small scrub brush and small trees like umbrella thorn (Acacia tortilis) that occasionally endure bouts with wildfires. Baobab (Adansonia digitata), lucky bean tree (Erythrina caffra), royal poinciana (Delonix regia) and miombo (Brachystegia spp. and Isoberlinia spp.) are a few trees adapted to the continual fluctuations between wet and dry; they bloom based on seasonal soil moisture levels and day length.
South American Plants
Outside of the continually moist and hot equatorial forest in Brazil, seasonal wet-to-dry weather occurs in parts of the Andes and in the subtropical areas in south-central South America. Lady-of-the-night (Brunfelsia americana) is one shrub triggered into flower by rains after the dry season according to Barwick. Yesterday-today-tomorrow (Brunfelsia grandiflora) blooms in the winter dry season but grows madly in the summer wet season. Other plants from South America native to wet and dry season regions include cockspur coral tree (Erythrina crista-galli), silk floss tree (Chorisia speciosa), guapirivu (Schizolobium parahyba) and pindo palm (Butia capitata).
While much of the Australian interior is arid year-round, coastal areas often enjoy a Mediterraneanlike climate with rains in winter and dry hot summers, or, around Darwin, definite monsoonal and dry seasons. Many species of gum trees (Eucalyptus spp, and Corymbia spp.) endure wet to dry climate areas, and nonda plum (Parinari nonda), wilga (Geijira slificolia) and various wattles (Acacia spp.) survive in alternating wet to dry cycles, blooming when day length, temperature or soil moisture dictate. In Queensland, penda trees (Xanthostemon spp.) flush into flower after rains break the annual seasonal droughts.