Describing a flowering plant

Botanists describe a plant in a fixed order: first its habit (herb, shrub or tree), then its vegetative characters (root, stem, leaves), then its floral characters (inflorescence and the parts of the flower). The description ends with a floral diagram and a floral formula.

A floral formula packs the whole flower into one line of symbols: Br bracteate; K calyx; C corolla; P perianth; A androecium; G gynoecium. A line below G (G underlined) means a superior ovary; a line above G means an inferior one. ⊕ means actinomorphic and ⚥ bisexual. Numbers give how many parts; brackets around a number show the parts are joined; a line drawn over two symbols shows one whorl is joined to another. Mustard (family Brassicaceae): ⊕ ⚥ K2+2 C4 A2+4 G(2).

A floral diagram is a top view of the flower. It shows how many parts there are, how they are arranged and how they relate. The mother axis (the stem the flower grows from) is drawn as a dot at the top. The whorls are drawn as rings: calyx outside, then corolla, then androecium, with the gynoecium in the centre.

Example: Solanaceae, the potato family. Herbs or shrubs. Leaves alternate, simple, without stipules, with reticulate venation. Flowers bisexual and actinomorphic. Calyx: five joined sepals that stay on the fruit (persistent), valvate. Corolla: five joined petals, valvate. Androecium: five stamens joined to the petals (epipetalous). Gynoecium: two joined carpels, superior ovary, two chambers, axile placentation. Fruit a berry or capsule; seeds with endosperm.

Solanaceae is a useful family: food (tomato, brinjal, potato), spice (chilli), medicine (belladonna, ashwagandha), fumigatory use (tobacco) and ornamental plants (petunia).