As familiar as weeds, as fragrant as mint, the Lamiaceae has a cosmopolitan distribution: about 7,850 species in 250 genera can be found almost worldwide (not Antarctica, and not north of the Arctic circle). Also known as the Labiatae, this family ranks 10th in size among native flowering plant families in North America, with about 408 species. In Maryland there are almost 100 species (more if you count sub-species and varieties), about half of which are in the piedmont. Sadly, only a little more than half of the species are natives, and of those, twenty-two are on the current Rare, Threatened and Endangered list. Two of those are extirpated.
Mint family plants are well known as garden ornamentals and herbs (culinary and otherwise). In the former category are agastache, bee balm (Monarda species), bugleweed (Ajuga species), catmints (Nepeta species), coleus, germander, hyssop, several sages (Salvia species), and stachys. Familiar kitchen species include basil, horehound, lavender, marjoram, the various mints, oregano, perilla, rosemary, savory, sage, and thyme.
The mint family shows up in another way in many of our homes: as furniture. The three species of teak trees (genus Tectona) are in the Lamiaceae.
The mint family species are generally herbs, shrubs, or subshrubs, frequently with hairy stems that are more often than not square in cross-section. The leaves are usually arranged in opposing pairs or in whorls on the stem, and are generally simple, though they may be lobed or pinnately or palmately compound, and they lack stipules. They often have oil glands (many species are fragrant).
The flowers are often found in whorls in the leaf axils, and are often scented. They generally have five fused sepals and five petals that are often fused or partly fused, giving the appearance of a two-lobed petal above and a three-lobed petal below.
In some Lamiaceae species flowers are borne in cymes, a type of inflorescence that has several branching pedicels originating from the same point on the peduncle, along with a terminal flower that is always the first to open. In the mint family these cymose flowers are often small and densely packed, with two opposing clusters; the effect is that of a whorl of individual flowers. Flowers can also be borne in racemes or panicles.
terminal panicle of horse balm (Collinsonia canadensis) —>
next time: lamiaceous weeds