How to Grow Milkweed
Asclepias syriaca
Milkweed is a tough, hardy perennial famous as the essential host plant for monarch butterflies. It thrives in full sun and well-drained soil of average to poor fertility — rich soil produces floppy growth. Plant in spring, spacing 60 cm apart, and be aware that it spreads aggressively via underground rhizomes. Use root barriers or plant in a contained bed to keep it in check. Cold stratification of seeds for 4-6 weeks improves germination. The plant dies back completely in autumn and is slow to emerge in spring — mark its position so you do not accidentally dig it up. The milky sap is a skin and eye irritant, so wear gloves when cutting.
Yearly Lifecycle
Care Essentials
Rarely needed — milkweed thrives in poor to average soil. A light compost mulch in spring is sufficient.
Watch For
- Aphids (oleander aphid is bright yellow)
- Milkweed bug
- Fungal leaf spot in wet seasons
Care Requirements
Light
Full sun essential
Needs full sun for sturdy, upright growth and best flowering. In shade, plants become tall, floppy, and flower poorly.
Watering
Drought-tolerant once established
Water young plants until established. Mature milkweed is very drought-tolerant and rarely needs supplemental watering. Avoid waterlogged soil.
Fertilizing
Rarely needed, lean soil preferred
Thrives in poor to average soil. A light compost mulch in spring is sufficient. Rich feeding produces floppy growth at the expense of flowers.
Pruning
Cut dead stems in late winter
Cut all dead stems to ground level in late winter or early spring before new growth emerges. Leave seed pods over winter for visual interest. Wear gloves as the sap is a skin irritant.
Growing Tips
Contain the spread
Milkweed spreads vigorously via underground rhizomes and can colonise a bed in a few seasons. Plant inside a buried barrier or in a large sunken pot to keep it where you want it.
Cold stratify seeds for better germination
Sow seeds in moist sand and refrigerate for 4-6 weeks before planting. This mimics winter conditions and dramatically improves germination rates.
Handle with gloves
The milky white sap that gives milkweed its name is a skin and eye irritant. Always wear gloves when cutting stems or dividing plants.
