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Large and hybrid bindweed identification and control
Information about the weeds, large bindweed and hybrid bindweed. Large bindweed is also known by its Latin name, Calystegia silvatica ssp. disjuncta and hybrid bindweed is also known by its Latin name, Calystegia x lucana.
About this weed
Both large bindweed and hybrid bindweed are weeds of concern in King County. This means due to how widespread they are, property owners are not required to control this species on their property, though it is recommended.
Large bindweed is known as Calystegia silvatica ssp. disjuncta. Hybrid bindweed is known as Calystegia x lucana. They are both in the morning glory family. Large bindweed is also known as greater bindweed. Both species are often confused for each other and the native hedge false bindweed (Calystegia sepium ssp. angulata). Another common name for all 3 species is morning glory.
Why it's a problem
Large bindweed is a fast-growing, herbaceous (not woody) vine that crowds out beneficial plants. It also damages them by adding weight and blocking light availability. Large bindweed can reduce years of yield in some crops. It can also increase the time and cost for harvest.
The extensive, spreading rhizomes (root system that spreads outwards and can grow new stems) break apart easily. Each root fragment can create new plants.
Large bindweed hybridizes with locally uncommon, native hedge false bindweed (Calystegia sepium ssp. angulata). As a hybrid, this bindweed will continue to mix with the parent large bindweed. A population will eventually inherit the competitive traits and impacts of large bindweed. It will be indistinguishable after a few generations.
Plant description
Large bindweed and hybrid bindweed are perennial (2+ year life cycle) herbaceous vines. They twine around other vegetation or fences for support and have large, white to pinkish, trumpet-shaped flowers.
Stems are light green to red, slender, twined, branched and mostly hairless. Leaves are sparsely distributed along the stems. They are roughly arrowhead-shaped with large rounded basal (grow at the bottom of the stem closer to the ground) lobes that vary in size and width.
Two large green leafy bracts (modified leaf) are found at the base of each flower. How far the bracts overlap and cover the sepals (leaflike flower part that encloses/supports the petals) help distinguish it from native hedge false bindweed (no overlap) and hybrid bindweed (some but less overlap).
Below ground the plants have extensive, white fleshy rhizomes and fibrous roots that may extend into the ground up to 10 feet. It is a common weed especially in developed areas, farms, shorelines, riparian areas, restoration areas and vacant lands.
Be aware of look-alike plants
The Flora of the Pacific Northwest was updated in 2018 and separated out the invasive, native, and hybrid bindweed.
Introduced large bindweed
- Larger flower
- Widening base below flower
- Round large saclike, overlapping bracts
- Larger leaves
- Larger (usually) rounded lobes on leaves
- Wider rounded sinuses (spaces between the lobes near the stem) at the bases of leaves
Native hedge false bindweed
- Smaller flower
- Tapering base below flower
- Angled bracts that don't overlap
- Smaller leaves
- 2-angled lobes at base of leaves near stem
- Narrower sinuses (spaces between the lobes near the stem) that form an angle at the bases of leaves
Hybrid bindweed
- Medium flowers
- Bracts that overlap somewhat but not completely
- Somewhat tapering base below flower
- Leaf size and features vary
For hybrid bindweed, sepals overlap but how much they overlap varies.
Field bindweed (Convolvulus arvensis) closely resembles large bindweed, but its leaves and flowers are smaller, and it tends to grow along the ground instead of climbing. It is a very problematic noxious weed in many crops.
When in doubt, take photos of the flowering parts (especially the bracts) and report them on iNaturalist.
What to do if you find it
A long-term management strategy that promotes the growth of desirable plants is the most effective method of controlling introduced bindweeds. Be sure to monitor the area for resprouts and seedlings after plants are removed.
Because introduced bindweeds are so widespread, property owners in King County are not required to control it. King County is not generally tracking infestations. We can provide advice on how to control bindweeds but there is generally no legal requirement to do so. The King County Noxious Weed Control Board recommends control of large and hybrid bindweeds where natural resources are being protected or as part of a stewardship plan. It may be difficult to distinguish large and hybrid bindweed from King County’s indigenous bindweed.
Control methods
We recommend using a combination of methods to control weeds. Prevention is the most effective bindweed control. Identify introduced bindweeds using the tools and techniques addressed below. In areas with few weeds, it is important to act quickly before they become harder to control. Make a long-term plan as it often takes several years to get rid of most weeds. Start in the least infested areas first and then move into more heavily infested areas.
Manual control
Carefully dig out plants, removing as much of the rhizomes as possible. Pulled plant parts can also be piled up on an elevated surface and dried out. Flowering and seeding plant parts should be bagged and put in the garbage.
Cultural control
Depleting the energy reserves of the roots over multiple seasons can help with control of introduced bindweeds. Establishing dense tree or shrub layers will eventually weaken bindweed populations. This will increase the effectiveness of other control methods. Grass or lawn sod layers with regular mowing and a bagged mower (to prevent distribution of vegetative plant parts) will also outcompete bindweed root systems over time.
Chemical control
Stay safe when using herbicide:
- Always read the label before use.
- Wear appropriate personal protective equipment (PPE).
- Follow state and local regulations.
A systemic herbicide can effective against bindweeds. Addressing the roots and rhizomes is a critical part of its control. Larger patches most likely will need an herbicide treatment in combination with other control methods to be effective.
Avoid spraying where herbicide may enter a waterway or wetland unless you are using a state-approved aquatic herbicide and have the required permits and licenses to do so. Use of pesticides in water is regulated in Washington state. See Washington Department of Ecology Aquatic Pesticide Permits [EXTERNAL LINK: Aquatic pesticide permits - Washington State Department of Ecology] for details. Always read the label before using herbicide and follow state and local regulations.
Spot treatments with combinations of triclopyr/picloram/aminopyralid, aminopyralid by itself, or glyphosate have been effective in summer or fall. The best time is before seed set in summer.
For large infestations, consider combining methods. Hand-pulling and the use of competitive beneficial plants in tandem will use less herbicide. Reduce bindweed cover before herbicide use by hand-pulling. Spray regrowth low to the ground so as not to damage nearby beneficial plants.
Always monitor sites for any plants that resprout and need follow up treatment. For more specific herbicide recommendations, see the link to Susceptibility of great bindweed to herbicides, produced by Massey University in New Zealand.
For more information or a site-specific control recommendation in King County, contact the noxious weed program. For information in other counties in Washington state, contact your local weed board or your local cooperative extension office.
Disposal instructions
Bag and dispose of all bindweed debris as plant fragments (especially roots) resprout when in contact with the ground to form new plants. Bindweeds are most commonly spread via rhizome fragments when yard waste is dumped and not disposed of properly.
Washington State Noxious Weed Control Board pamphlet on noxious weed disposal