Pale Smartweed (Persicaria lapathifolia) vs Spotted Ladysthumb (Persicaria maculosa)
This guide is under construction and has not been published yet. It may have errors. When in doubt, double-check other sources for definitive ID.These two species are frequently confused as both are annuals with densely-packed flower spikes of a similar range of colors. Their habitats overlap greatly and the two can grow together. The introduced P. maculosa is more likely to range onto mesic or even drier sites and is more tolerant of poor soils, whereas the native P. lapathifolia is more restricted to moist sites with rich soil and is more tolerant of ground-level competition.
Pale Smartweed (Persicaria lapathifolia) | Spotted Ladysthumb (Persicaria maculosa) |
 Sheath around each stem above each node have no bristles along their upper rim. Photo © Ryan Donnelly, CC BY 4.0. |  Sheath around each stem above each node has bristles along its upper rim. Photo © Matt Lavin, CC BY 4.0. |
 Spikes tend to be much longer and strongly drooping. Photo © Sandy Wolkenberg, CC BY 4.0. |  Spikes tend to be much shorter, and are usually held upright or only leaning slightly. Photo © Gavin Slater, CC BY 4.0. |
 Plants can grow much taller, commonly to 10dm (3 ft 3 in), sometimes even to 12dm (4ft). Plants can sprawl or lean but stems are more likely to stay upright, holding their own weight. Photo © Matthew Spoor, CC BY 4.0. |  Plants are usually shorter, only to about 7dm (2 ft 4 in.) Plants can be upright, but are more likely to sprawl or lean. Photo © Senna Bryce Robeson, CC BY 4.0. |
References & External Resources
These short lists show only links helpful for ID. For a complete list of references and resources also covering other aspects of ecology, visit the links section of the full article on each plant, which is the first entry here.
