Spirodela polyrrhiza is a species of perennialherb. They are native to Hawaii, U.S. Virgin Islands, The Contiguous United States, Puerto Rico, and Canada. They have green flowers.
Definition: Of plant duration, a plant whose life span extends over more than two growing seasons, c.f. annual, biennial, ephemeral, of flowering with respect to architecture, hapaxanthic, monocarpic, pleonanthic
Definition: A color hue with medium-low wavelength of that portion of the visible spectrum lying between yellow and blue, evoked in the human observer by radiant energy with wavelengths of approximately 490 to 570 nanometers.
Definition: The seasonal period in the U.S. during which the plant blooms the most. The bloom period is defined as the time when pollen is shed and stigmas are receptive.
Definition: The relative tolerance of the plant to calcareous soil. Calcareous soil is defined as soil containing sufficient free CaCO3 and other carbonates to effervesce visibly or audibly when treated with cold 0.1M HCl. These soils usually contain from 10 to almost 1000g/kg CaCO3 equivalent.
Definition: The ability of an organism to resist burning.
Comment: If a plant can carry a fire—and most can—it is scored as "not fire resistant" in the USDA PLANTS database where this characteristic is evaluated with reference to problem fires in California. http://plants.usda.gov/charinfo.html
Definition: Minimum tolerable rainfall (in inches), expressed as the average annual minimum precipitation that occurs 20% of the time (i.e., the probability of it being this dry in any given year is 20%) at the driest climate station within the known geographical range of the plant. geographical range of the plant. For cultivars, the geographical range is defined as the area to which the cultivar is well adapted rather than marginally adapted.
Comment: Minimum precipitation tolerance: Minimum tolerable rainfall, expressed as the average annual minimum precipitation that occurs 20% of the time (i.e., the probability of it being this dry in any given year is 20%) at the driest climate station within the known geographical range of the plant. Maximum precipitation tolerance: Maximum tolerable rainfall, expressed as the annual average precipitation of the wettest climate station within the known geographical range of the plant. For cultivars, the geographical range is defined as the area to which the cultivar is well adapted rather than marginally adapted.
