Hybrid watermilfoil
Myriophyllum spicatum × sibiricum · Aquatic plants
Photo: Bob / CC BY
Also called HWM, Hybrid milfoil
State noxious weed listing
- Idaho: Control
How to identify Hybrid watermilfoil
- Looks in between Eurasian and northern watermilfoil
- Usually 9 to 15 leaflet pairs per leaf
- Leaves somewhat limp out of water
- Positive identification needs a genetic test
Similar plants
Eurasian watermilfoil usually has more leaflet pairs and northern watermilfoil fewer, but leaf counts overlap, so only a lab test confirms the hybrid.
Growth profile
| Growing season | Starts growing early in spring, often ahead of the parent species, peaks in mid to late summer and keeps green stems through winter. |
|---|---|
| Starts growing | About 50 F water; early starter in low light |
| Light | Tolerates low light and turbid water |
| Depth | 2 to 15 feet, occasionally deeper |
| How it spreads | Stem fragments and root crowns; may also form winter buds |
| Habitat | Lakes, reservoirs and ponds where both parent species occur, especially nutrient rich water with soft bottoms. |
Why it matters in a lake
Often grows faster and more aggressively than either parent. It is widespread in Idaho waters and often mistaken for one of its parents.
Where it is found
- Idaho: Common
- Oregon: Occasional
- Wyoming: Not recorded
Classification
| Kingdom | Plantae |
|---|---|
| Phylum | Tracheophyta |
| Class | Magnoliopsida |
| Order | Saxifragales |
| Family | Haloragaceae |
| Scientific name | Myriophyllum spicatum × sibiricum |
Eurasian watermilfoil
Curly leaf pondweed
Brazilian elodea
Coontail
Elodea
Sago pondweed
Leafy pondweed
Common bladderwort
White water buttercup
Slender naiadNeed a hand?
Is it taking over your lake?
We identify what is growing, map how much of it there is and build a control plan that targets it without harming the rest of the lake.
Idaho / Wyoming (208) 501-4531Oregon (541) 280-0596