Swallow wort

Black & Pale swallow-wort 

Invasive Plant Factsheet: 

Vincetoxicum nigrum; syn. Cynanchum louiseae
Vincetoxicum rossicum; syn. Cynanchum rossicum

By Victoria Wallace, Alyssa Siegel-Miles, and Klaudia Sowizral, UConn Extension

Identifying Features

• OVERVIEW: Perennial, herbaceous climbing vine. 3-9 ft. long, spiraling around self and up other plants in extensive patches. Vines can also trail along the ground; the plant cannot stand upright without support. Laboratory studies have shown allelopathic effects (release of chemicals that suppress neighboring plants’ growth).

• LEAVES: Long, oval, and opposite, with a pointed tip; 3-4 in. long, 2-3 in. wide, with smooth edges; dark, glossy green, drying to bright yellow. Stems are twining; covered in downy hairs, clear sap runs when stem is broken.

• FLOWERS: Flat, star-shaped, with 5 fused petals, forming a short tube at the base. Flowers form in early summer and grow in clusters along the length of the stem. Black swallow-wort has dark purple, triangular petals about 1/8 in. long; pale swallow-wort has slightly longer, dull pink to burgundy petals.

• SEED: 1.5-3 in. long pods; smooth, slender, and resembling milkweed pods in both species. Pods change from green to yellow to brown, then split on one side to release mature windblown seeds in late summer to autumn. Flat, brown seeds are attached to white fluffy hairs, which help the seeds disperse.

• ROOTS: Dense and fibrous root system.

• REPRODUCTION/SPREAD: Capable of self-pollinating, although sexual reproduction is more common. Colonizes new sites by seed; once established, spreads locally via rhizomes. A square-meter stand can produce 1,000-2,000 seeds per year. Plants initially grow slowly and do not reproduce by seed for the first several years.

Why Use Native Plants?

Native Plants are What Nature Intended

Both nature and humanity wholly depend on native plants.

* Native plants are the foundation of healthy natural ecosystems. Plants, animals, fungi, and microorganisms have evolved together over millions of years. Their intricate web of relationships determines what can survive and thrive in a given place.

* Human activity has altered landscapes on an unprecedented scale, making the protection and restoration of native ecosystems essential.

* For people, planting native species creates resilient, low-maintenance landscapes that support pollinators, increase biodiversity, and help protect the ecosystems that sustain us.

Most Insects Need Specific Plants

Insect populations are declining across many regions, including many that species ecosystems depend on most. One major reason is the loss of the plants they need to survive.

The vast majority of North American caterpillar species, for example, can feed on only a small number of specific native plants.

Bolstering the Food Web

Pollinators—including birds, bees, and butterflies—that sustain local ecosystems and pollinate much of our food supply rely on native plants to complete their life cycles.

Specialized Adaptations Meet Specific Pollinator Needs

Many birds have coevolved with particular native plants and possess specialized features—such as the hummingbird’s long, curved bill and hovering flight—that allow them to reach into flowers insects cannot penetrate. They provide the only means for certain plant species to reproduce. Birds overall provide vital ecosystem services like insect pest control and long-range seed dispersal that insects generally do not.
Because native plants evolved alongside local insect pollinators, they provide the precise nectar, pollen, and host plants those species require. Many butterfly caterpillars, for example, can feed only on the leaves of specific native host plants. Insects that feed on native plants—especially caterpillars—are the primary food source for roughly 96% of terrestrial backyard birds raising their young.

Ecosystem Resilience

Native plants are naturally adapted to local climates and soils. They are better able to withstand weather extremes and changing climate conditions than many ornamental plants, while requiring far less human intervention.

Native Plant Benefits for You

Save Water and Money

Because they evolved in your region, native plants are adapted to local rainfall patterns and soil conditions, requiring less supplemental watering.

Avoid Chemicals

Once established, native plants require far less irrigation and fertilizer than turfgrass or many non-native ornamentals. They also reduce the need for chemicals that can harm people, pets, and pollinators.

Do Less Maintenance

Native plants have natural defenses against local pests and climate fluctuations, greatly reducing ongoing maintenance.

LINKS:

Why Use Native Plants 

How to Create a Native Garden

Native Plant Resources

CAGC - 2026 Project

How to Create a Native Garden

How to Create a Native Garden

Garden Creation Process

Whether you replace a plant, a small garden bed, or your entire landscape, every native plant you add makes a positive environmental impact. These are the key steps in creating a native plant-inclusive garden.

1. Evaluate

The first step is also the most important — understanding your site.

Determine:

- How much space you have
- How much sun and shade the area receives
- Whether your soil is sandy, clay, or loamy
- Whether it drains quickly or holds moisture

Nothing influences your success more than matching plants to your site’s conditions.

2. Specify

Create a list of plant characteristics based on your site’s conditions.

Be certain to consider: 

- Amount of sun and shade over the course of the day
- Soil type and moisture
- Preferred colors
- Plant form (habit)
- Desired maintenance level

Although most native plants require little care, some spread vigorously and may need occasional management.

3. Research and Select

Books, e-books, botanical gardens, native plant nurseries, and educational websites all provide valuable information. Particularly useful are online databases that let you search for plants based on your location and site conditions (see Native Plant Resources).

Visit nurseries and public gardens featuring native plants to discover what plants appeal to you, combinations you enjoy, and better understand what’s possible.

4. Design

Develop a planting plan based on mature size, bloom time, flower color, and plant form.

You can sketch your design, use online templates, and/or try digital planning sources and tools.  Homegrownnationalpark.org is at the top of our list.  Native Garden Planner.com can be helpful once you have an idea of what you want. 

AI design tools can also help, although less expensive versions may overlook important site considerations or unnecessarily complicate the process.  Native plant nurseries often provide basic design assistance.  Particularly if you are planning a large area, you might consider engaging a landscape professional to plan for you or with you. 

Planning should be enjoyable and educational. The more thought you invest, the more satisfying your garden will be. 

5. Foundational Design Guidelines

- Plant in drifts of at least three for visual impact and to help pollinators locate flowers.
- Place taller plants toward the back of beds and shorter plants in front.
- Include both warm and cool flower colors to attract a wide variety of pollinators:

Bees: blue, purple, violet, yellow, white
Butterflies: red, yellow, orange, pink, purple
Hummingbirds: bright red, pink, orange

6. Source

Demand for native plants continues to grow, although retail nurseries still focus primarily on non-native ornamentals.  Therefore, some native species can be difficult to find.

To avoid frustration, consider plant availability early in your planning, order ahead from native plant suppliers, build alternatives into your plan, and check online plant availability lists from native retailers. 
Here’s a list of local native plant growers:        ______________

7. Install

- Prepare the planting area by removing existing turf or weeds.

- Consider planting in early morning or late afternoon, when transplantation is less stressful for plants.

- Dig a hole two to three times wider than the root ball but no deeper than the container. Loosen the roots before placing the plant into the hole to encourage them to spread into the surrounding soil.

- Consider adding mycorrhizal fungi to the root zone to improve nutrient uptake and root establishment.

- If you plan to use mulch, position the plant’s root collar—the point where the roots become the stem—slightly above the surrounding soil level. When approximately 2 inches of mulch is added, the plant will be at the ideal level.

- Water thoroughly and immediately start the water schedule below. 

8. Care

- Water new plants three times a week for their first four weeks unless rainfall provides at least one inch of water in a week.  After that, let nature do most of the work, watering only during extended dry periods.

- Use mulch if you want to retain soil moisture, especially in the first season. This can be very helpful if you have dry soil and/or a windy site.   Keep mulch at least 2 inches away from the stem to prevent stem rot.  Over time, plants will fill out and mulch may not be required - this depends on your site’s conditions and your watering approach. 

- Ensure the mulch chosen does not include chemical dyes or additives. Leave stems and fallen leaves in place over the winter in plant beds - they provide habitat for beneficial insects, food for birds, and provide organic matter that enriches the soil.