There are four species in this group of Botrychium species
with broadly triangular blades over 10 cm wide (often at least
15 cm) and with the fertile branch diverging far below the base
of the sterile blade: B. multifidum, B. rugulosum,
B. oneidense and B. dissectum var. obliquum
(var. dissectum is more distinctive and does not usually
pose a problem). All four species bear
their blades more or less horizontal and close to the ground
and the point at which the fertile
branch diverges is often so low that it might appear to the
casual observer that the fertile and sterile branches arise separately.
There is usually just one blade per plant and the blade often
persists over winter. When the fertile branch is not present these
plants may easily be overlooked in spite of their substantial
size. Identification of these species may be difficult, even for
The criteria for distinguishing these species can be found at
steps 14-16 in the associated key.
Botrychium oneidense, like B. dissectum var. obliquum
tends to have the terminal portion of the pinnules less deeply
divided than in B. multifidum and B. rugulosum. Botrychium
dissectum var. obliquum has more acute blade segments
than B. oneidense. The reader is directed to the Flora
of North America, Vol. 2 for a more extensive description.
There are a few characteristics that can aid in the admittedly
difficult task of separating these species. Botrychium dissectum
blades often turn a bronze or brownish color late in the growing
season and they may also occur together with B. dissectum
var. dissectum, thereby providing a clue as to the identity.
The blade of Botrychium multifidum tends to run a little
larger than the other three species (though there is considerable
overlap in size) and may be the most common of the four species.
It can be numerous on some sunny sites, such as old pastures,
forest clearings and forest edges. B. oneidense tends to
be more associated with full or at least nearly full canopy and
moist, rich deciduous forests. If B. multifidum is found
under thoroughly canopied forests it is often sterile. B. rugulosum
appears to be quite rare in Wisconsin and perhaps throughout its
range. The habitat is unspecific, including "open fields
and secondary forests" as described in the Flora of North
B. multifidum apparently does best in forest clearings,
old fields and other sunny, grassy sites. It is also found in
deciduous forests, although it is often sterile there. It has
been reported across Canada, south to Pennsylvania, Minnesota
and North Dakota, and extending south to Utah and California in
the west. It is found throughout Wisconsin, but is apparently
more common in the north.