Aquatic Milkweed (Asclepias perennis)

Aquatic Milkweed

Also known as: Smooth-Seed Milkweed

The aquatic Milkweed is a welcoming flower to threatened monarch butterflies, with its dense clusters of pure white flowers, in the southeastern part of North America. It grows well in rain gardens, bog gardens and under standard garden conditions. Grows in continuously wet soil.

Scientific classification

Species

Aquatic Milkweed (Asclepias perennis)

Gentians, dogbanes, madders, and allies

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Toxic to Human & Pets

Toxicity

Weeds

Weed or not

Herb

Plant Type

Spring, Summer, Fall, Late winter

Bloom Time

91 cm to 1.8 m

Plant Height

5 cm

Spread

Green, Blue, White, Orange

Leaf Color

2.5 cm

Flower Size

White, Pink

Flower Color

Evergreen, Deciduous

Leaf type

Images of Aquatic Milkweed

Toxicity

Aquatic Milkweed contains toxic cardiac glycosides harmful to humans and animals. All parts are poisonous, posing a risk to children drawn by Monarch butterflies. Small doses cause diarrhea, nausea, muscle weakness, and confusion; larger doses lead to heart rhythm changes, seizures, respiratory paralysis, and death. Plant oils may also irritate skin and eyes.

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Weed Control

Aquatic Milkweed is native to North America. It acts as an important host for insects, including monarch butterflies, and is planted ornamentally. It is not listed as invasive at the state or federal level in the United States. However, aquatic Milkweed is toxic. It can spread by rhizomes in addition to seed, which can allow it to become weedy in ideal conditions with high water availability. Since aquatic Milkweed can regrow from rhizomes, manual removal is only effective if the entire plant is removed. Several herbicides have been effective in controlling weedy populations.

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Care Guide for Aquatic Milkweed

Every week

Water

Full sun

Sunlight

10 - 35 ℃

Ideal Temperature

Water: Adapted to wetland habitats, aquatic Milkweed thrives in consistently moist environments but tolerates moderate drought. Weekly watering mimics its natural hydration cycle. As an herbaceous perennial, its growth and flowering depend significantly on water availability.

Fertilize: Aquatic Milkweed requires minimal fertilizer, with organic fertilizer applied once before winter to enhance cold resistance. After flower buds appear, a phosphate fertilizer supports flowering. Avoid overfertilization to prevent nutrient buildup and root rot, ceasing fertilization during winter dormancy.

Pruning: To maintain aquatic Milkweed health, regularly remove infected plants and wilting leaves. In tropical/subtropical climates, prune branches in early spring to encourage growth. Due to high toxicity, handle aquatic Milkweed with gloves, keep it away from children, and avoid consumption.

Propagation: In early spring, aquatic Milkweed produces multiple small seedlings. Carefully dig out the seedlings, then use a sharp, clean knife to divide the root system into parts and plant them individually for propagation.

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Images of Aquatic Milkweed

Toxicity

Weed Control

Care Guide for Aquatic Milkweed

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