Data on vegetative reproduction, breeding system,
compatibility, pollination system, and shade tolerance are
from the Plants for a Future (2002) database (http://www.
comp.leeds.ac.uk/pfaf/). The Plants for a Future (PFAF)
database provides information on 3,121 USA species
(16% of the total plant species occurring in the USA). I
assumed that these 3,121 species are a random selection of
plants occurring in the USA. Data on vegetative reproduction
included biological (e.g., rhizomes, stolons, offsets,
etc.) and horticultural (i.e., can be “propagated by
division”) information. Because “propagation by division”
is an ambiguous term and its relationship to vegetative
reproduction is not well defined, I compared the results
from the PFAF database to reproductive data from
independent sources. The PFAF database provides “propagated
by division” information for 538 weed species
occurring in the USA. I had independent data on
vegetative reproduction for 493 (92%) of these species,
which indicated that 479 (97%) of them reproduced
vegetatively. Based on these results, I assumed that the
PFAF designation “propagated by division” implied
vegetative reproduction.