Trees or shrubs, evergreen or deciduous, usually with perfect flowers, rarely dioecious, monoecious, or andro-dioecious, usually with trichomes or rarely glabrous. Vegetative buds enclosed by hooded stipules. Stipules 2, connate and adnate to or free from petiole, splitting and caducous but with a remaining annular scar on twig or if adnate to petiole with scar on petiole. Leaves simple, spirally arranged, rarely distichous, sometimes fascicled on twig apex and becoming pseudoverticillate, petiolate; leaf blade pinnately veined, margin entire or rarely lobed. Flowers terminal or terminal on axillary brachyblasts, solitary, large, insect pollinated. Spathaceous bracts 1 to several, basal to tepals. Tepals 6-9(-45), in 2 to many whorls, 3(-6) per whorl, usually fleshy, sometimes outer ones (perules) nearly leathery or reduced and sepal-like. Carpels and stamens many, distinct, spirally arranged on an elongated torus. Androecium usually at basal part of torus; filaments thick and short, sometimes elongated; connective usually exserted and forming a long or short tip; anthers linear, with 2 thecae, introrsely, laterally, or rarely extrorsely longitudinally dehiscing. Gynoecium at apical part of torus, sessile or with a gynophore; carpels folded, usually distinct, sometimes connate at base or rarely completely connate; ovules 2-14 per carpel, in 2 series on ventral sutures. Fruit apocarpous or sometimes syncarpous; mature carpels usually dehiscing along dorsal and/or ventral sutures, rarely connate and irregularly dehiscing or (in Liriodendron) indehiscent, samaroid, and adnate to seed endotesta. Seeds 1-12 per fruiting carpel, pendulous on a filiform elastic funiculus, exserted from mature carpels; testa fleshy, red; endotesta bony; embryo minute; endosperm copious, oily.
Seventeen or two genera and ca. 300 species: mainly in SE Asia and Central America, E and S North America, including Mexico and Antilles, and N South America; 13 (one introduced) or two genera and 112 or 108 species including two to eight hybrid species (66 or 62 endemic, four introduced) in China.
Several species in the Magnolioideae are grown for their dried flower buds, known as xinyi (辛夷), which are used medicinally. In addition, HOUPOEA officinalis (Magnolia officinalis) is extensively grown for its medicinal bark. All species in the family are ornamental, and many are grown in public and private gardens throughout much of China and in other parts of the world.
One of the co-authors (Nooteboom) considers the Magnoliaceae to include two monogeneric subfamilies, with Magnolioideae containing the genus Magnolia and Liriodendroideae containing the genus Liriodendron. The reduction of the former genera of Magnolioideae to a single genus is based on DNA analysis (S. Kim et al., Amer. J. Bot. 88: 717-728. 2001; H. Azuma et al., J. Plant Res. 112: 291-306. 1999; H. Azuma et al., Proc. Int. Symp. Fam. Magnoliac. 1988, 219-227. 2000; H. Azuma et al., Amer. J. Bot. 88: 2275-2285. 2001; W. S. Judd et al., Pl. Syst. Phylogenet. Approach, 222-224. 1999) and morphology (R. B. Figlar, Proc. Int. Symp. Fam. Magnoliac. 1988, 14-25. 2000; R. B. Figlar & H. P. Nooteboom, Blumea 49: 87-100. 2004). In the present treatment, not only are previously recognized genera still included but additional new and/or reinstated segregate genera of Magnolioideae are recognized.
Nooteboom observes problems in the present treatment of segregate genera. An example of morphological similarity, which is strengthened by DNA results, is the similar fruit of Michelia species and Yulania (Magnolia) stellata. The present treatment distinguishes Michelia and Yulania on the basis of pseudoaxillary flowers in Michelia, but Y. stellata also has pseudoaxillary flowers. Furthermore, the emphasis given to fruit characters in order to separate genera is inconsistent, which renders the key to genera unworkable for specimens that lack fruit. Michelia (Magnolia) baillonii has fruit with connate carpels and is regarded as a Michelia species, although, even with fruit, it cannot be determined to Michelia and instead keys out as Talauma. The same character, fruit with connate carpels, is used to distinguish T. (Magnolia) hodgsonii from Lirianthe, even though, in the absence of fruit, it can hardly or not at all be distinguished from L. (Magnolia) henryi.
The following checklist is provided for the benefit of those who prefer to recognize Magnolioideae to include only the genus Magnolia. All the names in Magnolioideae accepted in the present treatment (in italics) are cross-referenced to the corresponding names in Magnolia (in boldface), with the latter followed by full bibliographic references. Except for treating Magnolioideae as monogeneric, the taxonomy at the specific and infraspecific levels in this checklist differs from the following main text of this treatment only in that one co-author (Nooteboom) considers that Magnolia fordiana var. calcarea, M. fordiana var. forrestii, M. figo var. crassipes, and M. figo var. skinneriana should be recognized rather than be treated as species.