Cleavers, Galium aparine

Life Cycle

Annual, Winter annual.


Reproducing only by seed.


Stems weak or reclining, 10-121cm long, square in cross-section with strongly ribbed corners, with very short, downward- or backward-pointing, firm, hair-like and curved bristles (a).


Leaves usually 3 to 8 in a whorl (b), linear, tapering at the base, mostly 1-8cm long, with bristles at the pointed tip (c), somewhat hairy on both surfaces and with many very short, backward-pointing bristles on the margins. These tiny hook-like bristles on stems and leaves cause them to cling together in masses and to cling to clothing, skin or fur, hence the common name, "cleavers."

Flowers and Fruit

Inflorescence mostly 1- to 5-flowered. The flowers are very small and soon replaced by the small spherical fruits (d). The fruits are bristly, 1.5-4mm in diameter. Flowers from May to August.

Roots and Underground Structures

Fibrous root system.


Cleavers is found in southern Ontario in woods, meadows, compost heaps, gardens and fields, and along roadsides and riverbanks.

Distinguishing Features

It is distinguished by its square, weak, clinging stems, its bristle-tipped leaves that also cling with backward-pointing bristles on the margins, and all leaves arranged in whorls of 3 to 8 at each node of the stem.

Figure #1.

A. Lower and upper parts of a mature plant. B. Portion of stem enlarged to show the backward pointing bristles (a).

Figure #2.

Cleavers small seedling.

Figure #3.

Cleaver flower and stem (b,c).

Figure #4.

Cleaver stem with seed pods (d).

Figure #5.

Leaf whorl with bristles (b) on the margins of each leaf and its pointed tip. Smooth bedstraw will not have bristles on its leaves.

Figure #6.

Young seedling plant.

Figure #7.

Mature plant.

Figure #8.

Figure #9.

Fibrous root system of cleavers.