Glossary

Perhaps one of the things that puts many people off trying to identify plants is the seemingly endless list of unfamiliar words, peculiar phrases and jargon that seem to accompany every book on plants. Though this site attempts to keep such words to a minimum, it is certainly true to say that the use of some special words or phrases does help to cut down on the verbage. For example writing "stipule" rather than "the small, flap-like appendages at the base of the leaf stalk" is certainly a lot quicker and more concise, so it is handy at times to use at least some of these words. The alphabetical list here covers a minimum of words that it is considered are worth learning to make the identification of plants just that little bit easier. The words are grouped into the sections of plants that they are most often used for.


Adventive: A plant that is not native to a region - and usually not fully established - but which will appear opportunistically if growing conditions are right. Most plants in this category tend to be short-lived 'weeds' of cultivated land or other disturbed areas.

Awn: A usually thin and hair-like extension at the tip of a larger structure. Most often used to refer to the spiked tips found on the flowers of many grasses.

Bract: A leaf-like growth found on a plant stem at the point where a flower is attached. Bracts often resemble the true leaves of the plant, but may also be more simple.

Bulbil: A small, vegetative growth produced by a few species of plant, usually found in either the leaf axils or flowerheads and usually capable of dropping off and growing to become a new plant.

Capitulum: When used in the context of flowers, this term usually refers to a compound flowerhead that is made up of many individual flowers, usually packed closely together.

Epiphyte: A plant found growing on another object, other than the ground, but not growing as a parasite. Such plants generally grow on trees in the tropics where they are able to obtain their water requirements from the atmosphere.

Floret: Usually used to refer to the collection of small parts that make up a single flower within a compound head of flowers. Most often used for grasses and members of the Asteraceae.

Glume: The small, scale-like, greenish outermost parts of a spikelet of grass flowers. Each spikelet of flowers or florets usually has two glumes at the base which may be of equal size or one larger than the other.

Inflorescence: A collective name for all parts of a flowering stem.

Leaf Node: The point where a leaf joins a stem. Can have important identification features in grasses and grasslike plants.

Leaflet: One section of a compound leaf.

Lenticel: Small marks on the trunk or branches of woody plants, through which gases are exchanged.

Ligule (flower): In the Asteraceae, what appears to be a single flower is usually a compound head of many flowers. The flowers toward the outer edge of this head bear a strap-like structure resembly a petal, formed by the fusion of several petals and known as a ligule.

Ligule (leaf): In grasses, the leaf has a sheath which wraps around the stem and a free part called the blade. Between the two parts is a small collar called a ligule. The ligule may be a membranous collar or a ring of hairs or bristles.

Ocrea: In the smartweed family, the ocrea is a membranous sheath around the stem at a leaf node.

Panicle: A type of inflorescence that is branched. Typically consists of a central stem with side branches.

Pappus: In the Asteraceae family, the familiar tuft of silky hairs that acts as part of the seed dispersal mechanism in dandelions and related species.

Pedicel: In plants that have more than one flower on a single stem, the individual stalk of each flower is called a pedicel.

Petiole: The stalk of a leaf, that joins it to a stem.

Phyllary: In the Asteraceae family, the outer segments of the compound head or capitulum. These segments are often narrow, pointed and overlapping, and usually green, but sometimes colored like the flowers.

Pinna: (Plural pinnae.) The primary side branch of a leaf, where the leaf is divided into more than one section. Most often used with reference to fern leaves.

Pinnule: The secondary sub-division of a leaf, where the leaf is divided into more than one section. Most often used with reference to fern leaves.

Pinnulet: The tertiary sub-division of a leaf, where the leaf is divided into more than one section. Most often used with reference to fern leaves.

Rachis/Rhachis: The central, linear part of a compound leaf, to which the primary divisions are attached. Seemingly spelt rachis in the US and rhachis elsewhere.

Rhizome: An undergound part of a plant which is actually not a root but a stem. Rhizomes are often capable of forming new plants if they break off from the original parent.

Sori: Plural of sorus - see below.

Sorus: A cluster of sporangia, the structures on ferns and their allies that produce spores (the fern equivalent of seeds). The Sori usually appear as brownish marks on the underside of a leaf, or in club-like structures that stand above the rest of the plant.

Spike/Spikelet: Where used with reference to flowers, the term spike is used where a number of flowers are all arranged along a common stem. Where the flowers are arranged in groups on more than one side branch, each side branch is called a spikelet.

Spore: Ferns and other closely-related groups such as horsetails and clubmosses do not produce seeds by direct fertilization from another individual plant. Instead, all plants produce asexual structures known as spores, microscopic particles that are released to the wind and which, at a later date, produce sexually reproductive structures, from which new plants eventually evolve.

Stem Node: An obvious bump or joint in an otherwise smooth stem; most often refered to in grasses.

Stipule: One of a pair of usually wing-like growths that can be found at the base of a leaf stalk, where it joins the stem.

Tepal: In some plants, the more traditional double row of sepals and petals is replaced by a single row of usually colored segments, called tepals.

Thallus: A term used for a basic plant structure that cannot be differentiated into other parts such as stems, leaves etc. Most often used for plant such as duckweeds and a stage in the reproductive stage of ferns.

Umbel: An inflorescence that has all the pedicels arising from a single point. Umbels can also be compound - effectively, an umbel of umbels.