This wildflower is a floating aquatic, producing a rosette of ascending
basal leaves. In a tropical climate, it is a perennial, while in a
temperate climate it is a summer annual that dies during the winter.
The blades of the basal leaves are 2-5" long and similarly across; they
are oval, orbicular, or orbicular-reniform in shape and their
margins are smooth (entire) and
slightly undulate. The blade surfaces are medium green, hairless, and
shiny. The petioles of the leaf blades are 2-7" long and conspicuously
swollen in the middle; they are medium green and hairless. At the base
petiole, there is an enveloping stipule about 1-3½" long. Each stipule
is light to medium green and hairless. From the center of the
rosette, there develops a stout flowering stalk about 2-10" tall that
is light green and glabrous to glandular-hairy. Small sheath-like
leaves clasp the lower stalk. Along the
upper two-thirds of each stalk, there is a spike-like panicle of 4-15
Each flower spans about 2-2½" across when it is fully open,
consisting of 6 lavender
tepals (rarely white or purple), 6 stamens (3 long stamens & 3
short stamens), and a 3-celled pistil with a single long style. In the
center of the uppermost tepal, there is a patch of purple with a large
yellow dot. The tepals have faint veins. The stout pedicels
are up to 1" long, light green, and glandular-hairy. In a
temperate climate, the
blooming period can occur from mid-summer to mid-autumn (throughout the
year in tropical climates), although the flowers of an individual plant
remain in bloom for only a few days. These flowers are diurnal, opening
up during the morning and withering by evening. Afterwards, the floral
stalk bends downward into the water, where the seed capsules develop.
Each capsule contains several seeds about 1-2 mm. in length and about
one-half as much across; they are broadly oblongoid, ribbed, and
pointed at one end. The seeds are distributed by water. The root system
consists of a crown with feathery fibrous roots. These roots are
purplish black and suspended in the water. Clonal daughter plants are
often produced by stolons along the surface of the water. Colonies of
floating plants often develop.
The preference is
full sun and stagnant or slow-moving water that contains adequate
amounts of absorbable nitrogen and mineral compounds. This plant is an
aggressive colonizer in subtropical and tropical climates.
In most of Illinois and other areas with colder temperate climates,
Water Hyacinth rarely, if ever, survives the winter, although
it may reseed
itself from time to time. This plant tolerates water that has
become polluted by heavy metals, but it does not tolerate brackish
water and salt water.
The introduced Water
Hyacinth rarely naturalizes in Illinois. So far, it has been reported
from Massac County near the southern tip of the state (see Distribution
A colony of this
plant has also been found in Vermilion County of
east-central Illinois, but it is unlikely to survive the winter at this
location. Water Hyacinth is native to tropical and subtropical areas of
South America. It was introduced into North America as an ornamental
plant for water gardens. In southeastern United States and southern
California, it has escaped from cultivation to become a serious
invasive pest, clogging canals and other waterways. It has also become
a pest on other continents in tropical and subtropical areas. Habitats
include canals, ditches, marshes, lakes, ponds, and slow-moving rivers.
Bodies of water in both degraded habitats and high-quality natural
areas can be invaded by this plant in part because it has few natural
enemies outside of its native range.
of the flowers are not well-known, but they are probably similar to
those of the native Pontederia
(Pickerelweed), such as
hummingbirds, long-tongued bees, and butterflies. Two native insects
feed on the foliage or suck plant juices from Water Hyacinth: they are
the larvae of Bellura
(Pickerelweed Borer Moth) and Rhopalosiphum
(Water Lily Aphid). Some insects have been
North America as biocontrol agents of Water Hyacinth: they are
(Chevroned Water Hyacinth Weevil), Neochetina
(Mottled Water Hyacinth Weevil), the larvae of
(Water Hyacinth Moth), and the planthopper Megamelus
. These biocontrol agents have been only
successful in controlling populations of this invasive plant. Two
native turtles, Stenotherus
(Stinkpot) and Trachemys scripta
(Slider), feed on the foliage of Water Hyacinth (Ernst et al., 1994).
A water garden in Champaign, Illinois.
The swollen petioles and its floating habit make this aquatic plant
relatively easy to identify, even when an inflorescence is not present.
The flowers of Water Hyacinth have a similar structure and coloration
to those of Pickerelweed (Pontederia
), except the flowers of
the latter are much smaller in size. Pickerelweed also differs by being
emergent aquatic with non-swollen petioles. Besides the well-known
Water Hyacinth, there are other Eichhornia
in South America, but
they have not appeared thus far in natural areas of Illinois.