Many are adapted for life in swamps and boggy places, while others thrive in the poorest of sandy soils or on the edge of saltpans.

Every species in the genus is an evergreen, and the leaves vary in size from minute and scale-like (M. micromera) to 270 mm (11 in) long (M. leucadendra).

Five sepals occur, although these are sometimes fused into a ring of tissue and five petals which are usually small, not showy, and fall off as the flower opens or soon after.

[10] The genus Callistemon was raised by Robert Brown, who noted its similarity to Melaleuca, distinguishing it only on the basis of whether the stamens are free of each other, or joined in bundles.

[11] Botanists in the past, including Ferdinand von Mueller and Lyndley Craven[12] have proposed uniting the two genera but the matter is not decided.

[2]: 16–17 [13][14] In 2014, Lyndley Craven and others proposed, on the basis of DNA evidence and a lack of morphological support,[14] that species in the genera Beaufortia, Calothamnus, Conothamnus, Eremaea, Lamarchea, Petraeomyrtus, Phymatocarpus and Regelia be transferred to Melaleuca.

[15] The World Checklist of Selected Plant Families maintained by the Royal Botanic Gardens, Kew lists Calothamnus and the other genera as synonyms of the accepted genus Melaleuca.

[2]: 26–31 Melaleucas are mostly pollinated by insects, including the introduced honey bee (Apis mellifera), flies, beetles, wasps and thrips.

[2]: 23 [19] Some species of Melaleuca, especially M. alternifolia, are cultivated for the production of tea tree oil, and in plantations are susceptible to a number of insect pests.

Native stands have fewer predators, but tea tree sawfly (Pterygophorus species) and longicorn beetles are often found.

[20] The scale insect Beesonia ferrugineus forms round, fluffy-looking galls on branches of several Melaleuca species.

[22] Melaleuca quinquenervia (broad-leaved paperbark) is the most damaging of 60 exotic species introduced to the Florida Everglades to help drain low-lying swampy areas.

[26] Aboriginal Australians used several species of Melaleuca to make rafts, as roofing for shelter, bandages, and food preparation.

[36] Tea trees (spelled Ti-Trees) are specifically mentioned in the lyrics of a short aria 'Joy' published around 1916 by J.D.Fletcher & Co of London, by Australian composer Arthur Chanter (1866-1950).