Heartshape false pickerelweed (Pontederia vaginalis)

Synonyms: Monochoria vaginalis

Common Names: False pickerelweed, heartleaf false pickerelweed, oval-leaf pondweed

Description:

Heartshape false pickerelweed (Pontederia vaginalis) is an aquatic plant from Asia and the Pacific that is one of the worst weeds of flooded rice fields and can spread into wetlands [2][3]. MISIN tracks it because it is a US Federal Noxious Weed and an early-detection target ? it is not yet in the Midwest, and catching it early is the best way to keep it out [1][2].

Habit:

Heartshape false pickerelweed is a small, shiny aquatic plant that grows rooted in shallow, still water, usually about 8 to 20 inches tall [3]. Its leaves rise in a low tuft from the base, each on its own stalk, and the leaf blade is glossy, deep green, and shaped like a spade or heart ? rounded to heart-shaped at the base and pointed at the tip [2][3]. In the flowering season it sends up a short stalk holding just a few (usually two to eight) violet to blue-purple flowers in a small, loose cluster [2]. Look for it in flooded, wet places ? the edges of ponds and ditches, marshes, and especially flooded rice or other crop fields [2][3]. It is easiest to spot when it is in flower and its shiny, heart-shaped leaves stand above the water [2].

At-a-glance cues:

1. A small aquatic plant, about 8 to 20 inches tall, in shallow still water [3]
2. Glossy, deep green, heart- to spade-shaped leaves in a low tuft [2][3]
3. Just a few (about 2 to 8) violet to blue-purple flowers in a small, loose cluster [2]
4. Grows in flooded, wet places ? pond and ditch edges, marshes, and flooded fields [2][3]

Leaves:

1. Arrangement: rising in a low tuft (rosette) from the base, each leaf on its own stalk [2][3]
2. Shape: blade oval to broadly egg-shaped, with a heart-shaped or rounded base and a pointed tip [2]
3. Surface: glossy and hairless, deep green [3]
4. Veins: several curved veins running the length of the blade [2]

Stems:

1. Habit: a stemless, fleshy aquatic herb, usually 8 to 20 inches tall, rooted in shallow water or wet mud [3]
2. Roots: has a short underground stem (rhizome) and spreads a short distance by creeping stems [2][3]

Flowers:

1. Color: violet to blue-purple [2]
2. Shape: small flowers with six petal-like parts, each flower about half an inch across [2]
3. Arrangement: just a few flowers ? usually two to eight ? in a small, loose cluster on a short stalk [2]
4. Bloom time: during the warm growing season [2]

Fruit and seeds:

1. Fruit: a small capsule, about half an inch long, that splits open to release the seeds [2]
2. Seeds: very many ? a single plant can produce roughly 30,000 seeds [3]
3. Germination: the seeds sprout at different times rather than all at once, which makes the plant hard to control [3]
4. Dispersal: seeds move in water and in mud on boots, tools, boats, and equipment; the plant also spreads a short distance by its creeping underground stems [2][3]

Habitat:

Heartshape false pickerelweed is native to southern and eastern Asia, the Pacific islands, and western Australia [2][3]. It grows in shallow, still or slow-moving fresh water and wet ground at low elevations ? flooded rice and crop fields, marshes, ditches, ponds, and the slow edges of rivers ? and it does best where the ground stays flooded [2][3]. In the United States it has become established only in California and Hawaii so far, which is why early detection elsewhere is so important [2].

Reproduction:

Heartshape false pickerelweed spreads mostly by seed, and it makes an enormous number of them ? a single plant can produce about 30,000 seeds [3]. The seeds travel in water and in wet mud carried on boots, tools, boats, and farm equipment, so they move easily between flooded fields and wetlands [2][3]. They also sprout at different times rather than all at once, so new plants keep coming up over a long period, which makes the weed hard to clear [3]. The plant spreads a little more by its short underground stems, building a patch where it takes hold [2][3]. Because it seeds so heavily, the key is to remove plants before they flower and set seed [3].

Impact and Damage:

Heartshape false pickerelweed is mainly a problem in flooded fields and wetlands rather than in yards, and it is not known to be poisonous [2][3]. It is one of the most serious weeds of flooded rice around the world: it competes with the crop for light, space, and nutrients and can sharply cut rice yields [2][3].

In natural areas, it can invade marshes, ditches, and other shallow wet habitats and crowd out native water plants [2]. In California it is considered a threat to vernal pools ? seasonal wetlands that support rare native plants [3]. Because it is a US Federal Noxious Weed, moving or importing it is restricted at the federal level, and it is a target for early detection and rapid removal before it can establish [1][2].

Similar species:

Pickerelweed (Pontederia cordata) is a common native wetland plant and the look-alike this weed is named after ("false pickerelweed") [4]. Both are shallow-water plants with glossy, heart-based leaves and blue-purple flowers, but the flowers set them apart: native pickerelweed carries a tall, dense spike packed with many small lavender-blue flowers, while heartshape false pickerelweed has only a few flowers in a small, loose cluster [4]. Native pickerelweed also grows taller and forms large stands along shorelines [4].

Monitoring and rapid response:

Signs to watch for:

1. A small, shiny aquatic plant with heart- to spade-shaped leaves in a low tuft, in shallow still water [2][3]
2. A few violet to blue-purple flowers in a small, loose cluster on a short stalk [2]
3. New plants in a flooded field, ditch, marsh, or pond edge ? especially anywhere it has not been seen before [2][3]

What you can do:

1. Because this is a Federal Noxious Weed that is not yet established in the region, the most important step is to report it right away (see below) so experts can confirm it and respond quickly [1][2].
2. For a small or new patch, hand-pull the whole plant, roots and all, before it flowers and sets seed ? this works but takes persistence because seeds keep sprouting [3].
3. Bag and dispose of all plant parts, and clean mud, seeds, and fragments off boots, tools, boats, and equipment before leaving the water so you do not spread it [2][3].
4. For a larger area, a crew can hand-remove small, outlying patches first and return over the season and following years to catch new plants as seeds keep germinating [3].

When to call a professional:

1. Larger stands, or any plants in open water, ponds, or flooded fields, are best handled with a land or water manager ? aquatic work usually needs special permits [2].
2. Because it seeds so heavily and the seeds sprout over a long period, established infestations need a coordinated, repeated plan over several years [3].
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. USDA NRCS Plants Database. Pontederia vaginalis (Burm. f.) C. Presl ex Kunth. plants.usda.gov
2. U.S. Fish & Wildlife Service. "Pickerel Weed (Pontederia vaginalis)." fws.gov
3. California Department of Food and Agriculture. "False Pickerel Weed (Pontederia vaginalis) ? Pest Rating Proposal." cdfa.ca.gov
4. North Carolina Extension Gardener Plant Toolbox. Pontederia cordata (pickerelweed). NC State Extension. plants.ces.ncsu.edu

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