Including Tiliaceae of Michigan Flora. This is an easily recognized family, with palmately veined leaves and flowers with stamens united (monadelphous) into a column around the carpels (except in Tilia). The flowers of Hibiscus, of which a number of species are familiar ornamentals in warm climates or greenhouses, are typical. There are other Malvaceae grown for their flowers, and cotton (Gossypium spp.) is useful both for the hairs on its seeds and for the oil in them. The mucilaginous juice often found in the family has led to the use of several species for assorted culinary purposes.
1. Trees; with inflorescence apparently borne at the middle of a tongue-shaped bract.
1. Herbs or shrubs; inflorescences various, but never with a large, tongue-shaped bract.
2. Plants true shrubs (to 5 m tall); flowers ca. 6–10 cm wide, borne singly in the axils of basically three-lobed leaves.
Hibiscus (in part, H. syriacus)
2. Plants fully herbaceous, flowers and leaves various, but not combined as above (except in Hibiscus laevis).
3. Calyx without bractlets at its base.
4. Calyx with some unbranched hairs (especially on margins) over 0.5 mm long; leaf blades cordate, acuminate, densely velvety-pubescent beneath; carpels more than 10 at least in the larger flowers, with beaks becoming ca. 4–5 mm long in fruit.
4. Calyx finely (mostly stellate-) pubescent, all hairs shorter than 0.5 mm; leaf blades not cordate (ovate-elliptic, oblong, or deeply lobed), lightly velvety to glabrous beneath; carpels 5 or 10, with beaks ca. 1 mm long or less, or essentially beakless.
5. Flowers perfect; leaves ovate-elliptic, oblong, or deeply 3–5-lobed, with the central lobe clearly the longest.
5. Flowers unisexual; leaves palmately lobed, the larger with 5-11 or more ± equal lobes.
3. Calyx with bractlets at its base additional to the 5 sepals.
6. Bractlets subtending the calyx 3 (or fewer).
7. Blades of all leaves shallowly (if at all) divided or lobed (less than halfway to their base).
Malva (in part, couplet 3)
7. Blades of at least mid- and upper cauline leaves divided below the middle into coarsely toothed or pinnatifid lobes.
8. Plant erect, with linear-lanceolate stipules; petals obcordate (notched at tip, sometimes with additional irregular teeth); most if not all pedicels shorter than petals at anthesis.
Malva (in part, couplet 2)
8. Plant prostrate or trailing, with broadly ovate stipules; petals truncate or rounded (not notched, but rather finely erose at tip); most if not all pedicels longer than petals at anthesis.
6. Bractlets subtending the calyx at least 6.
9. Carpels (and styles) numerous (more than 15), forming in fruit a ring of 1-seeded indehiscent mericarps that separate from a central axis; bractlets subtending calyx triangular.
10. Stem with ± scattered, mostly bristly hairs, the surface fully visible; petals over 3 cm long; carpels more than 20.
10. Stem (especially upper portion) covered with dense velvety gray pubescence; petals less than 2.5 (–3) cm long; carpels ca. 20 or fewer.
9. Carpels (and styles) 5, forming in fruit a single capsule; bractlets subtending calyx narrowly linear.
11. Capsule more than twice as long as broad; calyx tube (splitting on one side) at least 3 times as long as the lobes; corolla yellow.
11. Capsule scarcely if at all longer than broad; calyx tube at most about equaling the lobes (or slightly longer if inflating in fruit); corolla, at least at base, purple or pink (or white).
Hibiscus (in part)