Plants annual or perennial herbs or less commonly shrubs or trees, often with stellate pubescence. Leaves alternate and sometimes also basal, simple, petiolate, sometimes shallowly to deeply lobed (occasionally appearing nearly compound), the main veins or lobes usually palmate. Stipules hairlike, scalelike, or somewhat leaflike, sometimes shed early. Inflorescences terminal and/or axillary racemes, panicles, clusters, or solitary flowers, sometimes with bracts at the branch points, these sometimes shed early. Flowers mostly perfect (pistillate flowers sometimes mixed with the perfect ones), hypogynous, actinomorphic. Sepals 5, fused into a cup or tube, at least toward the base (free in Tilia), sometimes closely subtended by 2 or more bractlets. Petals 5, often fused to the base of a staminal tube. Stamens numerous (5 in Melochia), the filaments united most of the way into a tubular column (except in Tilia), the anthers usually each with a single locule opening by a longitudinal slit. Staminodes absent (present and petaloid in Tilia). Pistil 1 per flower, composed of 5 to numerous fused carpels (in some genera these loosely fused and tending to separate in fruit), the superior ovary with 3 to numerous locules, the styles as many as the locules, fused into a tube toward the base (entirely fused in Gossypium and Tilia, free in Melochia), each branch with 1 globose to disc-shaped or club-shaped stigma or a linear stigmatic region toward the tip. Fruits longitudinally dehiscent, globose to ovoid capsules with 1 to several seeds per locule, or schizocarps with a flattened ring of as many mericarps as locules, each with 1 to several seeds, or nutlike drupes (in Tilia). About 204 genera, about 2,330 species, nearly worldwide, especially in tropical regions.

Pubescence types are an important feature in distinguishing some closely related species in the family. For purposes of the following treatment, three different hair types are mentioned. Simple hairs are unbranched individual hairs, which may be relatively stouter, longer, and more or less spreading, or may be fine and appressed. The bases may be unmodified or somewhat expanded and bulbous (pustular). Stellate hairs have three or more arms from the base and are mostly relatively fine (exceptions exist) and appressed. Fasciculate hairs are generally spreading, relatively stout and long, and usually have pustular bases. They presumably represent stellate hairs with spreading arms, as well as clusters of simple hairs with the bases fused. For the most part, these hair types are distinguishable only with magnification.

The Malvaceae are here defined in a broad sense, to include Missouri genera traditionally segregated in the Sterculiaceae and Tiliaceae (Cronquist, 1981, 1991). The family is recognized by the presence in many (but not all) members of a staminal tube, as well as palmate leaf venation, stellate pubescence, and the production of mucilaginous sap. Molecular studies (summarized by C. Bayer et al., 1999; Alverson et al., 1999) have suggested that the woody families Bombacaceae, Sterculiaceae, and Tiliaceae, among others, should be included in an expanded concept of Malvaceae, which has rendered what was once an easily recognizable group into one whose morphological characteristics are somewhat less easily defined. However, molecular evidence is fairly strong that such families are embedded within Malvaceae in the traditional sense, and that, if separated, none of these families would comprise a natural group. To avoid potential accusations of narrow-mindedness (Mabberley, 2008), the family is here grudgingly treated in the broad sense. Within the Malvaceae, there exist nine major lineages that have been treated as informal groups equivalent to subfamilies. The “Tilioideae” group comprises the former Tiliaceae, and members of the former Sterculiaceae are included in two groups, “Byttnerioideae” and “Sterculioideae” (Whitlock et al., 2001).

Numerous species of Malvaceae have showy flowers and are cultivated as ornamentals. Tilia is a popular shade tree that also is used for fiber, furniture, musical instruments, utensils, and crafts. Other economically important timber species include Ochroma pyramidalis (Cav.ex Lam.) Urb. (balsa, formerly Bombacaceae). Cotton, one of the world’s most important natural fibers, is derived from the long hairs covering the seeds of several Gossypium species, and the genus also is the basis for cottonseed oil. Cultivated food plants in the family (in the broad sense) include okra (Abelmoschus esculentus (L.) Moench) and durian (Durio zibethinus Rumph. ex Murray). Species in several genera also have economic importance as crop weeds. Marshmallow, originally prepared from the mucilaginous root extract of the European Althaea officinalis L. (marsh mallow) whipped with sugar and egg whites, is now made instead from corn syrup, gelatine, sugar, and egg whites. Cocoa is derived from the seeds of the neotropical tree Theobroma cacao L. and kola nuts (responsible for the flavor of cola beverages) comes from the edible seeds of species of the African genus Cola Schott & Endl. (both of these formerly Sterculiaceae). A number of species in this group contain compounds that are cardiac stimulants and thus have been used medicinally and pharmaceutically.