The Apiaceae, also known as Umbelliferae, is the 16th largest plant family in the world (1), with almost 3,800 species in over 300 genera (2). Plants in this family are found almost everywhere (except Antarctica), but mainly in northern hemisphere temperate regions and tropical highlands. Within the US, the Apiaceae is the 11th largest family, with 349 (native) species.

Sixty-five species of umbellifers can be found in the state of Maryland, though 28 of these are non-native, and many of those are waifs (plants that are alien and known to be present, but not in established populations). Of the 65, maybe half are present in the piedmont.

Umbellifers are usually herbaceous and can be annual, biennial, or perennial. Although identifying individual species can be difficult, as a family they are easy to recognize. There are always exceptions, but general characteristics to help you identify them include:

• hollow stems (between the nodes)
• sheathing at the nodes
• compound or twice-compound pinnate or palmate leaves, arranged alternately
• aromatic foliage
• seeds enclosed in schizocarps (a dry, often woody fruit)
• tiny flowers arranged in umbels or more often compound umbels

This last characteristic is the one from which the older family name is taken. An umbel is an arrangement like an umbrella, with pedicels (individual flower stalks) all growing from the same point. In a compound umbel, multiple secondary peduncles originate from one point and terminate in individual umbels, with pedicels and flowers arising from these.

Few plant families have such easily identifiable inflorescences, but be careful: getting the details right can mean the difference between life and death. Literally. More in the next few posts.

(1) Wikipedia
(2) Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 12, July 2012 [and more or less continuously updated since] (Missouri Botanical Garden)