Native to Chesapeake Bay except for N. minor; non-invasive
Family - Najadaceae
Distribution - Four naiad species occur in Chesapeake
Bay. The first two are more common than the latter two.
Najas guadalupensis
(southern naiad or bushy pondweed)
Najas minor (no common name)
Najas
flexilis (northern naiad)
Najas gracillima (slender naiad).
Naiads are native except for N. minor which was introduced from Europe. Naiads
grow in small freshwater streams, and freshwater portions of Bay tributaries.
Bushy pondweed tolerates slightly brackish water. Naiads prefer sandy substrates
and tolerate relatively low light.
Recognition - Naiads vary in size from inch-high tufts
on sandy bottoms to highly branched plants two or three feet high on silty
bottoms. In general the naiads have slender, branching stems with narrow leaves
that broaden at the base and are opposite or in whorls. Naiads have small,
fibrous roots without rhizomes or tubers. The four species in Chesapeake Bay
resemble one another, however, their leaves provide distinguishing
characteristics. Bushy pondweed and northern naiad have wider leaves than the
other two species. Bushy pondweed leaves are flat and straight, whereas leaves
of northern naiad curve out from the stem at maturity. Slender naiad and N.
minor have slender leaves with a truncated (abruptly-ending) basal sheath. N.
minor is distinguished from slender naiad by stiff, recurved leaves and
lengthwise ribs on its seed coat. Slender naiad has minute leaf-margin teeth
that are difficult to see, whereas leaf-margin teeth of N. minor are visible to
the naked eye.
Ecological Significance - N. guadelupensis and N.
flexilis are considered to be excellent food sources for waterfowl. All
parts of the plants (stems, leaves and seeds) are eaten by a variety of
waterfowl including lesser scaup, mallards and pintails. The other two species
of Naiads are less important due to their scarcity (N. gracillima) and
low nutritional value (N. minor).
Similar Species - Naiad species are similar in appearance. All
are difficult to distinguish without the use of a handheld lens and some
experience.
Reproduction - Reproduction occurs primarily by seed formation
in late summer. Male and female flowers are located on leaf axils. The seeds
that develop after pollination have surface markings, and each species has its
own characteristic seed surface markings. Finally, seed germination and plant
growth occur in spring.
