Anchored water hyacinth (Eichhornia azurea)

Synonyms: Pontederia azurea, Piaropus azureus

Common Names: Rooted water hyacinth, anchored waterhyacinth

Description:

Anchored water hyacinth (Eichhornia azurea) is a free-flowering aquatic plant from Central and South America, and a close relative of the notorious common water hyacinth [1][2]. Unlike that floating cousin, this plant is usually rooted in the mud with long stems that trail across the water, forming dense mats of round, glossy leaves and showy purple-blue flowers [1][2]. MISIN tracks it because it is a U.S. Federal Noxious Weed: it is illegal to sell or move across state lines, and where it escapes into warm waters it can choke ponds and waterways [2].

Habit:

Anchored water hyacinth is a rooted aquatic perennial with long stems ? up to about 26 feet (8 m) ? that creep and float across the water surface and form dense stands [1]. Its floating leaves are round and glossy green, roughly the size of your palm, carried on slender leaf stalks [1]. This is the key difference from the common water hyacinth: those slender stalks are not swollen into the bulb-like floats that the floating water hyacinth uses to stay up [1][2]. It also produces fan-like leaves underwater [2]. In the warm season it bears showy spikes of mauve-blue to purple flowers, each with a yellow spot, looking much like lilac blooms ? the easiest time to spot and identify it [1].

At-a-glance cues:

1. Rooted plant with long trailing stems forming dense floating mats [1]
2. Round, glossy, palm-sized floating leaves on slender stalks ? not bulb-like floats [1][2]
3. Showy mauve-blue to purple flowers with a yellow spot, in lilac-like spikes [1]
4. Fan-shaped leaves growing underwater below the floating ones [2]

Leaves:

1. Arranged alternately along the stem [1]
2. Floating leaves round, glossy green, with a blade roughly 3 to 6 inches (7?16 cm) across [1]
3. Carried on slender leaf stalks (petioles) that are not inflated into bulb-like floats ? unlike common water hyacinth [1][2]
4. Also produces fan-like leaves below the water surface [2]

Stems:

1. Herbaceous aquatic perennial, normally rooted ("anchored") in bottom mud rather than free-floating [1][2]
2. Long trailing and floating stems, up to about 26 feet (8 m), that form dense stands [1]
3. Spreads sideways by creeping runners (stolons) and roots from the stem [1]

Flowers:

1. Showy and lilac-like, mauve-blue to purple with a yellow spot and a purple center [1]
2. Borne on erect spikes, with roughly 7 to 50 flowers per spike [1]
3. Bloom in the warm season; pollinated by bees and butterflies [1]
4. Each flower has both male and female parts (perfect) [1]

Fruit and seeds:

1. Produces many tiny seeds, about 1.5 to 2.6 mm long [1]
2. Also spreads readily without seed, by runners and by broken stem fragments [1][2]
3. Fragments break off in wind, current, or from animals and drift to start new plants [2]

Habitat:

Anchored water hyacinth grows in warm, still or slow-moving fresh water ? ponds, lakes, marshes, canals, and the quiet edges of slow rivers ? usually rooted in the mud in shallow water with its stems trailing across the surface [1][2]. It is native to Central and South America, where it is common in lowland waters such as the Amazon, the Pantanal wetlands, and the Parana river system [1][2]. In the United States it has turned up in scattered warm-climate states, including California, Texas, Florida, Mississippi, and Virginia, and in Puerto Rico [1]. As a Federal Noxious Weed it is the target of efforts to keep it from establishing more widely [2].

Reproduction:

Anchored water hyacinth spreads quickly, and mostly without seed [1]. Its stems creep outward by runners and root as they go, so a single plant widens into a dense mat [1]. Pieces of stem break off easily in wind, current, or from animals and float away to start new plants somewhere else [2]. People move it too ? as a water-garden ornamental, or when pond or aquarium plants and their fragments are dumped into natural water [2]. It also makes large numbers of tiny seeds, pollinated by bees and butterflies [1].

Because it regrows from fragments and runners, the key to control is removing the whole plant and every loose piece before a mat can rebuild [1][2]. For a regulated plant like this one, the most valuable action is catching it early and reporting it before it spreads [2].

Impact and Damage:

Anchored water hyacinth is not poisonous to people or pets, but it is one of the more damaging aquatic weeds where it takes hold [2]. It forms thick mats across the water surface that block sunlight from reaching the plants below, killing submerged native vegetation, and that lower the oxygen in the water as the dense growth decays ? which harms fish and other aquatic life [2]. The mats clog ponds, canals, and waterways, shutting down boating, fishing, and swimming, and the still water they create can breed mosquitoes and harbor disease-carrying organisms [2]. Its close relative, the common water hyacinth, is considered one of the world's worst aquatic weeds, and anchored water hyacinth carries the same potential ? which is why it is regulated at the federal level [2].

Similar species:

Anchored water hyacinth is mixed up with other floating or purple-flowered water plants. The rounded glossy leaves on slender (not bulb-like) stalks and the lilac-like purple flowers are the best clues.

Common water hyacinth (Eichhornia crassipes) is the closest look-alike and a relative. It floats completely free rather than rooting in mud, and its leaf stalks are swollen into spongy, bulb-like floats that anchored water hyacinth lacks [1][2].

Pickerelweed (Pontederia cordata) is a native relative with similar blue-purple flower spikes. But it is firmly rooted in shallow water, has firm heart- to arrowhead-shaped leaves on upright stalks, and does not float or form surface mats [1].

Water lettuce (Pistia stratiotes) also floats and forms mats, but it grows as a pale green, ribbed, lettuce-like rosette and has tiny, inconspicuous flowers rather than showy purple ones [1].

American frog's-bit (Limnobium spongia) is a small free-floating plant with glossy rounded leaves, but it is much smaller, lacks the long trailing stems, and does not have the showy purple flowers [1].

Monitoring and rapid response:

Signs to watch for:

1. A rooted aquatic plant with long trailing stems and round, glossy, palm-sized floating leaves on slender stalks (not bulb-like floats) [1][2]
2. Showy mauve-blue to purple, lilac-like flowers with a yellow spot in the warm season [1]
3. Expanding mats covering the surface of a pond, canal, or slow waterway [2]
4. New growth where water-garden or aquarium plants may have been dumped [2]

What you can do:

1. Never buy, plant, or release this species ? it is a Federal Noxious Weed, and moving it is illegal [2]
2. If you think you have found it, report it right away ? early detection is the most useful step for a regulated plant not yet established [2]
3. In a small pond you own, rake or pull out the floating mats and remove rooted plants with as much of the root as possible, taking care to collect every loose fragment [1][2]
4. Bag and dispose of all plant material in the trash on land ? never compost it or return pieces to the water, where fragments re-root [1][2]
5. Natural area crews and lake managers should treat any find as a rapid-response priority, remove entire mats and fragments, and monitor the site over the season [1][2]

When to call a professional:

1. Any find of this federally regulated plant ? contact your state aquatic invasive species program or land manager for guidance [2]
2. Large mats, or any infestation in flowing water or water you cannot fully clear by hand [2]
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. U.S. Geological Survey, Nonindigenous Aquatic Species Database. Eichhornia azurea (anchored waterhyacinth) ? Species Profile. nas.er.usgs.gov
2. Texas Invasive Species Institute. Eichhornia azurea ? Anchored Water Hyacinth. tsusinvasives.org
3. USDA NRCS PLANTS Database. Eichhornia azurea (Sw.) Kunth (EIAZ2). plants.usda.gov

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