Life cycle: Erect summer annual.
Leaves: Cotyledons are narrow oval to lance-shaped with rounded tips. Leaves are alternate, lance-shaped with pointed tips and smooth margins, usually hairless and occasionally with a purple watermark.
Stems: Branched, erect up to 4 feet tall and jointed with swollen nodes. A smooth, membranous sheath (ocrea) surrounds the stem at the base of each petiole.
Flowers and fruit: Small, pink to white flowers form in dense, spikelike clusters at the tips of stems. The seed is enclosed in a single-seeded, flat, glossy black, round to oval fruit with a pointed tip.
Reproduction: Seeds. |
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Ladysthumb (P. persicaria L.) Differs by having a fringe of bristly hairs at the top of the ocrea. Usually has a purple watermark on leaf.
Pale smartweed (P. lapathifolium L.) Differs by having young leaf undersides with whitish hair, older leaf undersides with yellow glands and a nodding inflorescence.
Swamp smartweed (P. amphibium var. emersum Michx.) Differs by having perennial, creeping, woody rhizomes and usually hairy foliage; found in wetter environment. |
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| Hairy foliage of swamp smartweed. |
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| Pennsylvania smartweed leaf. |
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| Left: Pennsylvania smartweed ocrea. Right: Ladysthumb ocrea. |
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| Pennsylvania smartweed immature flower cluster. |
Pennsylvania smartweed seedling. |
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