Ornamental · Pontederiaceae
Pickerelweed
Pontederia cordata
A cold-hardy native emergent that raises blue flower spikes all summer, requiring only full sun and a saturated root zone.
Full sun
USDA 3–10
2–4 ft · 0.6–1.2 m
Overview
Pickerelweed is a native aquatic of pond edges, ditches, and slow streams throughout much of North America. It anchors in the mud at the water's edge and carries its leaves and flower spikes clear of the surface, the habit that defines an emergent marginal. Glossy, heart-shaped leaves furnish the base of the clump, and from early summer into fall it produces soft spikes of violet-blue flowers.
Its ecological value is considerable. The flowers supply nectar to bees and other pollinators, while ducks and waterfowl consume the seeds and foliage. As a hardy herbaceous perennial it withstands winters from zone 3 through zone 10, retreating to the rhizome each fall and resprouting from that reserve in spring.
Two factors govern success. The root zone must remain constantly wet to shallowly submerged, because this wetland species has no drought tolerance, and the vigor that clothes a pond edge in bloom will spread if left unchecked. Growing it in a basket where space is limited holds it to a generous, well-mannered clump.
Care
The short version: site it in full sun with a permanently wet root zone, rooted in rich mud or loam under just a few inches of water, and contain the rhizomes in a basket so they don't overrun the planting.
Light
Flowering is strongest in full sun, which drives both spike production and vigorous growth. The plant tolerates partial shade, but reduced light yields fewer flowers and a looser, leggier habit.
Water
As a true wetland plant, its roots must stay constantly wet to shallowly submerged and never dry out. Root it in mud or rich loam under about 2 to 12 inches (5 to 30 cm) of water over the crown, or in boggy soil at the water's edge. Setting it deeper than roughly 12 inches (30 cm) puts excess water over the crown and can kill it.
Soil
It requires rich organic loam or mud held constantly wet to submerged. Its pH tolerance is wide, spanning 6.0 to 8.0, so most pond mud supplies suitable conditions without amendment.
Temperature
The species is exceptionally cold-hardy, enduring -40°F (-40°C) in dormancy and about 100°F (38°C) in summer. That amplitude corresponds to zones 3 through 10, allowing it to overwinter in place across most of the country.
Humidity
Rooted in or beside water, it is never short of atmospheric moisture, so humidity requires no management. The high humidity of a pond margin matches its native conditions.
Feeding
Nutrient demand is low and the plant is largely self-sufficient. To encourage growth, insert an aquatic plant tablet into the soil during the spring-through-summer season, but feed lightly, since it performs well unaided.
Pruning
Maintenance is minimal. Remove spent flower spikes as they fade through the season, then cut back and clear the old, dead foliage in late fall or early spring ahead of new growth.
Repotting
Every 2 to 3 years, lift the plant to divide and refresh a congested clump. The indicators are rhizomes bulging the basket, smaller leaves with reduced flowering, and the crown heaving up out of its pot.
Size & spacing
Mature plants reach 2 to 4 feet (61 to 122 cm) tall and 18 to 24 inches (46 to 61 cm) across. Allow each clump room to expand, and note that the rhizomes will keep advancing past that spread unless a basket restrains them.
When to plant
Pickerelweed tracks the warm season. Establish divisions or potted plants in spring after the last frost, setting them into pond-margin mud or a submerged basket, and expect blue spikes from early summer through fall.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to early spring; seed germinates best under water and may need cold stratification
- Plant: Spring, after frost, into mud at pond margins or in submerged baskets
- Harvest: Early summer into fall (about June to October)
Hardiness
USDA hardiness zones: 3–10
Temperature: down to -40°C
Troubleshooting
Because pickerelweed hosts no serious pests or diseases, nearly every problem traces to one of two causes: its spreading habit, or a lapse in the wet conditions it requires. Diagnose against the entries below and correct the cause before the colony overreaches or the plant declines.
Wilting and browning from drying out or wrong planting depth
As an obligate wetland species, this plant depends on a saturated root zone and cannot recover from drying out. Soil that turns dry or merely damp, or a crown submerged beyond roughly a foot, stresses the plant into browning and stalled growth. Restore a constantly wet to shallowly submerged root zone, and reset the depth so only 2 to 12 inches (5 to 30 cm) of water stands over the crown.
Fix:
- Keep the soil constantly wet to shallowly submerged at all times
- Reset the planting depth so only about 2-12 in (5-30 cm) of water covers the crown
- Move container plants to a shallower shelf or raise them on bricks
Spreading rhizomes that crowd a small pond or container
The plant's thick rhizomes are storage and spreading organs, and in open pond mud they extend rapidly to build dense colonies that advance into open water and over adjacent marginals. Because the rhizome is what travels, confining it in a submerged aquatic basket from planting keeps the root mass where it belongs. Lift and divide the clump every 2 to 3 years to relieve congestion, and cut back outlying shoots before the colony broadens.
Fix:
- Grow in a submerged aquatic basket or container rather than open mud to confine the rhizomes
- Lift and divide clumps every 2-3 years, discarding excess rhizome
- Pull or cut back outlying shoots to keep the colony in bounds
Minor leaf feeding from aphids, mites, or caterpillars
Pickerelweed is subject to no serious pests or diseases, so what shows up on the foliage is generally incidental feeding. Sap-sucking aphids appear in clusters, spider mites leave fine webbing and stippling as they pierce leaf cells, and caterpillars remove tissue at the margins. A strong jet of water dislodges the small feeders, caterpillars come off by hand, and a plant kept in good vigor outgrows the modest damage.
Fix:
- Hose pests off with a strong jet of water
- Hand-pick caterpillars
- Tolerate minor damage, since this plant has no serious insect or disease problems and usually outgrows it
Toxicity
For households and gardens this is straightforward: pickerelweed is non-toxic to people and animals, and portions of it are edible. The young leaves and ripe seeds have a long record of human use, and the plant is established forage for ducks and other wildlife. Because it grows in standing water, the only meaningful precaution is routine supervision around a pond.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
The foliage holds no compounds toxic to cats, so an exploratory nibble carries no risk of poisoning. The standing water it grows in is the only reason to keep normal supervision.
Dogs None
With no toxic constituents in the tissue, a dog that ingests a mouthful of foliage faces no danger from the plant itself.
Horses Safe
Nothing in the plant is toxic to horses, so grazing the leaves along a pond margin does them no harm.
Rabbits Safe
The tender foliage contains no toxins that would affect rabbits, which makes it a reliable marginal near a hutch or pond.
Livestock Safe
Cattle, goats, and sheep can browse it without harm, since the plant is non-toxic and serves as forage for a range of grazing and wild animals.
Birds Safe
The seeds and foliage rank as prized forage for ducks and other waterfowl rather than a hazard, and pose no risk to backyard or wild birds.
People Safe
The young leaves and ripe seeds are edible for people. Prepare young leaves as a cooked green, and take the ripe seeds raw or roasted.
No special handling precautions; the plant is safe and even edible. It lives in standing water, so normal supervision around ponds applies.
Varieties
The straight blue-flowered species accounts for most plants in trade, though two selections merit attention.
'Alba'
A white-flowered selection that raises tall spikes of white blooms from summer into fall in place of the species' blue.
var. lancifolia
A botanical variety marked by narrower, lance-shaped foliage rather than the heart-shaped leaves of the typical plant.
Companions
Pickerelweed plays well with other native marginals and pond plants that share its taste for full sun and wet ground, layering the pond edge with different heights and leaf shapes.
Plant near
Water lily (Nymphaea): A classic pond pairing: pickerelweed's vertical blue spikes at the margin complement floating-leaved water lilies in deeper water.
Arrowhead (Sagittaria latifolia): Another native marginal sharing the same shallow-water, full-sun habitat for a layered pond-edge planting.
How to propagate
Pickerelweed propagates by two methods, one appreciably faster to establish than the other.
DivisionEasy
Spring · One growing season
Division is the most reliable method because it works with the plant's spreading rhizome. In spring, lift an established clump and sever the thick rhizomes into sections, retaining roots and at least one shoot on each. Each section resumes growth from its existing reserves and reaches full size within a single growing season.
SeedModerate
Late winter to spring · One to two growing seasons
Seed is the slower route and is best sown from late winter into spring. Germination is strongest under water, even after dry storage, and a period of cold stratification improves it by breaking dormancy. Allow seed-raised plants one to two growing seasons to build the reserves needed for full size.
Myths
Pickerelweed is the same plant as water hyacinth and just as invasive.
The two are distinct species with different habits. Pickerelweed is a native rooted emergent that anchors in pond mud and holds its position, whereas water hyacinth is a free-floating species notorious for choking waterways. Both belong to the family Pontederiaceae, but pickerelweed is a well-behaved native, not the invasive floater.