Moderate water; irrigate deeply and allow the upper few inches of soil to dry between waterings. Young plants need more consistent moisture. Established plants tolerate some drought, but Phoenix summers generally require supplemental irrigation.
Size
2-3 ft tall × 1-2 ft wide
Habit
Perennial clump
Toxicity
Toxic — Pets Humans & Livestock
Description
Common milkweed is a rhizomatous perennial with broad leaves and fragrant flower clusters. ‘Red’ is not a well-established cultivar of Asclepias syriaca; verify the plant’s identity, since red milkweed commonly refers to other species. Details below apply to A. syriaca, which is poorly suited to Phoenix’s extreme summer heat.
Toxic to pets, livestock, and humans if ingested (cardiac glycosides); milky sap is a skin/eye irritant
Care Instructions
Light: Full sun in cooler climates; in Phoenix, provide morning sun and afternoon shade, avoiding reflected heat.
Water: Moderate water; irrigate deeply and allow the upper few inches of soil to dry between waterings. Young plants need more consistent moisture. Established plants tolerate some drought, but Phoenix summers generally require supplemental irrigation.
Soil: Well-drained sandy loam to clay loam. Tolerates varied soils, including moderately alkaline soil; avoid persistently saturated conditions.
Mature size: 3–5 feet tall and about 1–3 feet wide per clump; underground rhizomes can form much wider colonies.
Bloom: Typically late spring through summer; flowering may be limited or shortened by extreme Phoenix heat. Seed-grown plants may take two or more years to bloom.
Evergreen / deciduous: Herbaceous deciduous perennial; stems normally die back during dormancy.
Growth rate: Moderate initially, becoming fast and colony-forming once established under favorable conditions.