Aquatic Milkweed

Asclepias perennis

Other common name(s):

White Swamp Milkweed

Family:

Apocynaceae (Dogbane Family)

Plant Ecoregion Distribution Map

Gulf Coast Prairies and Marshes, Western Gulf Coastal Plain
Northern Humid Gulf Coastal Prairies
Flatwoods, Southern Tertiary Uplands

Plant Characteristics

Growth Form

Herbaceous

Height

1.5
to
2
ft.

Spread

0.5
to
1
ft.

Leaf Retention

Deciduous

Lifespan

Perennial

Habitat and Care Requirements

Soil Type(s)

Sand, Loam, Rich, Moist, Mud

Light Requirement

Sun, Part Shade

Water Requirement

Medium

Native Habitat

Wetland or Riparian

Bloom and Attraction

Bloom Color

White, Pink

Bloom Season

Spring, Summer

Seasonal Interest

Nectar, Pollen, Larval Host

Wildlife Benefit

Butterflies, Bees

Maintenance

Low maintenance. Can grow in moist or wet soils. Works well in rain gardens. Native Habitat: hydrated soils, floodplains, water way margins, marshes, cypress swamps, ditches, and wet lands. WARNING: all parts toxic. Propagation: seeds, cuttings, root divisions.

Comments

Blooms May-September. The white to pink flowers are arranged in a flat panicle. Leaves are short and narrow on purple stems. The fruit is a smooth pod containing many seeds that lack the usual tufts found in milkweeds. Although still listed by some in the Asclepiadaceae Family, the majority of botanical organizations now list it in the Apocynaceae Family. Larval host: Monarch Butterfly.
Material Treatment Method Collection References
Seed Stratification Use Pro-mix BX with biofungicide moistened and placed in heavy plastic trays. Compact the soil somewhat to prepare a firm seedbed. Spread seed evenly on the soil surface and then cover with 1/4 inch of additional soil. Press top layer down slightly to ensure good seed to soil contact. Place trays in a cooler (34 degrees) for 30 days to allow for cold, moist stratification. After cold stratification, move trays directly to the greenhouse for germination. Seedlings begin to emerge after about 2 weeks in the greenhouse. Once the seedlings have developed sufficient root systems, transplant into quart plastic containers filled with Metro-mix 510 growing media for 5 months. Move plants into a shadehouse to allow for hardening for 2 weeks. Seed pods were placed in a breathable cloth bag to allow for air drying. Seed pods were opened to remove the enclosed seeds. The seeds were cleaned by hand to separate the seeds from the fluffy hairs. 1) chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.nrcs.usda.gov/plantmaterials/wvpmcot12252.pdf 2) https://earthone.io/plant/asclepias%20perennis?srsltid=AfmBOooEZKm6H4LxBVSzC18mybRs7WoOhquYyuORsY89ma6T16zUkk3R 3) https://monarchbutterflygarden.net/milkweed-for-monarchs/asclepias-perennis/
Stem Cutting Cuttings should be taken during the growing season and placed in water or a moist soil mix until roots develop. 1) https://earthone.io/plant/asclepias%20perennis?srsltid=AfmBOooEZKm6H4LxBVSzC18mybRs7WoOhquYyuORsY89ma6T16zUkk3R 2) https://monarchbutterflygarden.net/milkweed-for-monarchs/asclepias-perennis/

About the Region

Fall Symposium 2025 Logo - Teach for the Future

Salado, the location of our Fall 2025 Symposium, lies at the intersection of two ecoregions: the Edwards Plateau (Limestone Cut Plain) and Blackland Prairie (Northern Blackland Prairie).

The Edwards Plateau area is also called the Hill Country; however, this general term covers a much larger area extending farther north. Spring-fed creeks are found throughout the region; deep limestone canyons, rivers, and lakes (reservoirs) are common. Ashe juniper is perhaps the most common woody species found throughout the region. Additional woody species include various species of oak, with live oak (Quercus fusiformis) being the most common. Sycamores (Platanus occidentalis) and bald cypress (Taxodium distichum) border waterways. This area is well known for its spring wildflower displays, though they may be viewed in spring, late summer, and fall, as well. According to Texas Parks and Wildlife, average annual rainfall in the Edwards Plateau ranges from 15 to 34 inches.

The Blackland Prairie extends from the Red River south to San Antonio, bordered on the west by the Edwards Plateau and the Cross Timbers, and on the east by the Post Oak Savannah. Annual rainfall averages 30 to 40 inches, with higher averages to the east. This region is dominated by prairie species. The most common grass species include little bluestem (Schizachyrium scoparium) and Indian grass (Sorghastrum nutans) in the uplands and switchgrass (Panicum virgatum) in the riparian areas and drainages. Common herbaceous flowering plants include salvias, penstemons, and silphiums. This area has suffered greatly from overgrazing and agricultural use. Few intact areas remain, though many of the plants can be found along county roadsides throughout the region.

Our four host chapters (New Braunfels, Lindheimer, Guadalupe, and the Hill Country chapters) are located in one or both of the ecoregions above. However, the eastern portion of Guadalupe County also falls within the Post Oak Savanna ecoregion. Annual rainfall averages 35 to 45 inches, with higher averages to the east. A wide variety of hardwood trees are found, including several species of oaks, elms, and in the Bastrop area, loblolly pine (Pinus taeda). Grasses and forbs dominate in the open savannas, with most common grass being little bluestem. Ranching, agriculture, and fire suppression have allowed woody species to encroach on the once-open savannas.

Source: Wildflowers of Texas by Michael Eason