Pennywort  (Hydrocotyle sp. )

Pennywort is a perennial broadleaf plant with creeping underground stems. One species, lawn pennywort, Hydrocotyle sibthorpioides, is found in the South Coast of California to about 1100 feet (330 m). Another species, floating pennywort, Hydrocotyle ranunculoides, is scattered throughout California, except for the Great Basin and deserts, up to 4900 feet (1500 m). Floating pennywort grows on land or in water.  It usually forms dense low-growing mats on wet soil near water or in shallow water. Small colonies can float independently. Floating pennywort is generally considered desirable in aquatic ecosytems. However, because of its creeping habit, it can be problematic in irrigation and drainage ditches. Sold as an aquatic or pond ornamental, floating pennywort has escaped cultivation in some locations.

Seedling

Seedling leaves in both lawn pennywort and floating pennywort are alternate to one another along the stem. Lawn pennywort cotyledons (seed leaves) are egg shaped and less than 1/12 of an inch (2 mm) in length. They have a rounded to slightly indented tip. The first few leaves are roundish to kidney shaped, about 1/12 to 1/6 of an inch (2–4 mm) long and 1/8 to 1/5 of an inch (3–5 mm) wide, and are deeply lobed at the base. Leaves are hairless and have five to seven shallow lobes on the edge.

Mature plant

In both floating pennywort and lawn pennywort leaves are hairless, stems root at joints (nodes) and leaf stalks have papery structures (stipules) at their base. Leaves are round or kidney shaped, and are alternate to one another along the stem. Floating pennywort has fleshy leaves, mostly 2/5 to 3 inches (1–8 cm) wide, that are deeply lobed or have smooth to scalloped edges, and sometimes have a reddish spot at the point where the leaf stalk attaches to the stem. Lawn pennywort leaves are usually 2/5 to 4/5 of an inch (1–2 cm) wide and are shallowly lobed with finely scalloped margins.

Flowers

Small white or greenish flowers with five petals cluster on a flowering stalk called an umbel stalk, forming an umbrellalike flower head.

Floating pennywort blooms from March through August; five to ten flowers each with their own stalks attach to the umbel stalk, which is 2/5 to 2-2/5 inches (1–6 cm) long, forming a dense flower head.

Under conducive conditions, lawn pennywort blooms almost year-round; its flower head is composed of three to ten flowers that do not have their own stalks, but that attach directly to the umbel stalk, which is about 1/5 to 3/5 of an inch (0.5–1.5 cm) long.

Fruits

The Fruits are flattened and separate into halves at maturity. Each half contains one seed. Floating pennywort seeds are on stalks, football shaped to round, and 1/25 to 1/8 of an inch (1–3 mm) long with inconspicuous ribs. Lawn pennywort fruit do not have stalks, are round, about 1/25 to 1/21 of an inch (1–1.2 mm) in diameter, and have conspicuous ribs.

Reproduction

Reproduce by seed or from sprouts that grow from creeping stems and stem fragments.

More information

• Broadleaf ID illustration
• Floating pennywort, Hydrocotyle ranunculoides Calflora's distribution map
• Lawn pennywort, Hydrocotyle sibthorpioides Calflora's distribution map
• For agriculture: UC IPM Pest Management Guidelines