Curly-Leaf Pondweed Identification & Treatment
Scientific Name: Potamogeton crispus Category: Submerged Tier: 1 — High-Priority — Most prevalent and/or most damaging across the US
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Identification
Curly-leaf pondweed has distinctive wavy or crinkled leaf margins that make it relatively easy to identify. Leaves are oblong, 1–3 inches long, and alternate along the stem. They are somewhat translucent with a reddish-brown to olive-green color and conspicuously wavy (crisped) edges — resembling lasagna noodles. Key distinguishing features:
- Wavy, crinkled leaf margins (unlike any native pondweed)
- Reddish-brown to olive-green color
- Leaves alternate (not whorled) along the stem
- One of the first submerged plants to appear in spring — grows under ice
Commonly confused with: Other pondweeds (check for wavy leaf margins — unique to curly-leaf), clasping-leaf pondweed (leaves clasp the stem, margins not wavy)
Treatment
Recommended Natural Waterscapes Products:
- Aquathol K or Aquathol Super K (endothall) — Highly effective on curly-leaf pondweed, especially applied in early spring during active growth before turion production. Early treatment (when water temperatures reach 50–60°F) is critical to prevent turion formation.
- Harvester (diquat) — Contact herbicide for spot treatments.
Timing is critical: Treat curly-leaf pondweed in early spring before it produces turions (hardened overwintering buds). Once turions form, they drop to the sediment and will produce new plants the following year regardless of treatment.
Full Profile
- Native Range: Europe, Africa, Asia, Australia
- US Distribution: Found in at least 45 states. Most problematic in northern EPA ecoregions: Northern Lakes and Forests, North Central Hardwood Forests, Northeastern Highlands, Western Corn Belt Plains. USDA Zones 3–8.
- Regulatory Status: Listed as invasive in many states, particularly in the Midwest and Northeast. Not federally listed.
- Habitat: Lakes, ponds, slow rivers. Tolerates turbid, nutrient-rich water. Grows in 1–15 feet of water.
- Reproduction: Primarily by turions (hardened leaf buds) that are produced in late spring/early summer and sink to the sediment. Turions can survive for years. Also fragments.
- Ecological Benefits: Because curly-leaf pondweed grows and peaks earlier than most native species (spring rather than summer), it can provide early-season fish habitat. However, when it dies back in early summer, the rapid decomposition of large plant biomass releases nutrients that fuel mid-summer algae blooms — a significant water quality problem.
- Seasonal Behavior: Unusual life cycle: begins growing in fall, continues growing under ice in winter, reaches peak biomass in late spring, then dies back completely by mid-summer. This is the opposite of most aquatic plants and is a key identification clue.
Sources: Texas A&M AquaPlant – Curly-Leaf Pondweed | MSU Extension
Related Species
- Hydrilla (Hydrilla verticillata) — Submerged, Tier 1
- Eurasian Watermilfoil (Myriophyllum spicatum) — Submerged, Tier 1
- Coontail (Hornwort) (Ceratophyllum demersum) — Submerged, Tier 1
- Elodea (Common Waterweed) (Elodea canadensis) — Submerged, Tier 1
- Egeria (Brazilian Elodea) (Egeria densa) — Submerged, Tier 1
- Sago Pondweed (Stuckenia pectinata (formerly Potamogeton pectinatus)) — Submerged, Tier 2
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