Canadian Clearweed vs Black-fruited Clearweed
These species can be virtually impossible to distinguish without looking at their seeds, but are usually easily distinguished by seeds. Magnification is helpful. There are average differences in shininess and transluscence of leaves, which can be a clue on some individuals, but these qualities have considerable overlap and are also dependent on lighting. P. pumila ranges farther south in the west and central portions of its range. P. fontana ranges farther west in the northern parts of its range. It is less common throughout, but may be underreported due to difficulty of identification and the fact that this genus is often overlooked. Their habitat preferences are similar but P. fontana is more restricted to calcium-rich substrates and is relatively more likely in wetlands; it may also venture into slightly sunnier conditions.
Canadian Clearweed (Pilea pumila) | Black-fruited Clearweed (Pilea fontana) |
An annual with transluscent stems and foliage found in a wide variety of lightly-shaded wet areas. | An annual usually restricted to calcareous substrates in or near wetlands. |
 Seeds are paler, either uniformly lighter, or streaked with lighter purple. Photo © Ryan Sorrells, CC BY 4.0. |  Seeds are black or very dark purple, nearly uniform in color except for a faint green border, which may not be visible without magnification. Photo © Ryan Sorrells, CC BY 4.0. |
 Seeds are either mostly smooth, or have only slightly raised ridges. Seeds average smaller, being more-or-less similar in length but slightly narrower (0.6-1.1 mm.) Photo © Zihao Wang, CC BY 4.0. |  Seeds have raised pebble-like bumps when viewed under close magnification. Seeds average larger, being more-or-less similar in length but slightly wider (1-1.5 mm.) Photo © Zihao Wang, CC BY 4.0. |
 Foliage tends to be shinier. Photo © Tom Scavo, CC BY 4.0. |  Foliage tends to be less shiny. Photo © Derek, CC BY 4.0. |
 Leaves average more transluscent. Photo © Sarah Johnson, CC BY 4.0. |  Leaves average more opaque, less transluscent. Photo © Ryan Sorrells, 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.
