Asclepias verticillata (Whorled Milkweed) Growing Guide
Site Selection
Sunlight: Whorled milkweed thrives in full sun, needing at least 6 hours of direct sunlight daily.
Soil: It prefers dry to medium moisture, well-drained soils. It can tolerate a variety of soil types, including sandy, loamy, and even rocky soils, as long as they are not consistently wet.
Location: Choose a sunny spot in your garden, meadow, or naturalized area. Whorled milkweed is a great addition to butterfly gardens or areas where you want to support pollinators.
Direct Sowing Outdoors
Fall Planting:
Sow seeds in the fall, a few weeks before the first expected frost. This allows the seeds to undergo natural stratification over the winter.Preparation:
Scatter the seeds evenly over the soil surface. Gently press them into the soil or cover with a very thin layer of soil (no more than 1/4 inch).
Water the seeds gently but thoroughly. Keep the soil consistently moist until germination.
Spring Planting:
Sow seeds in the spring, after the last expected frost.Preparation:
Scatter seeds and press them lightly into the soil, covering with a thin layer of soil (no more than 1/4 inch).
Water gently and keep the soil consistently moist until germination.
Starting Seeds Indoors
Timing: Start seeds indoors 6-8 weeks before the last expected frost in your area.
Preparation: Use seed starting trays or pots filled with a well-draining seed starting mix.
Sowing: Sow seeds about 1/4 inch deep in the seed starting mix.
Stratification: Whorled milkweed seeds benefit from cold stratification to improve germination rates. You can mimic this by placing the seed trays or pots in the refrigerator for 4-6 weeks before sowing.
Germination: Keep the seed starting mix consistently moist and provide adequate light (grow lights or a sunny window). Germination typically occurs within 1-3 weeks.
Transplanting: Once the seedlings have developed a few sets of true leaves, they can be transplanted outdoors. Harden off the seedlings gradually by exposing them to outdoor conditions for increasing periods each day before transplanting.
Seed Scarification
While not strictly necessary, scarification can improve germination rates. You can scarify the seeds by gently rubbing them with sandpaper or soaking them in hot water for a few minutes.
Maintenance Tips
Watering: Once established, whorled milkweed is drought-tolerant. Water occasionally during prolonged dry spells, but avoid overwatering.
Fertilizing: Whorled milkweed does not require heavy fertilization. A light application of a balanced fertilizer in the spring can be beneficial.
Deadheading: If you want to prevent self-seeding, remove seed pods before they mature and split open.
Pest and Disease Control: Whorled milkweed is generally pest and disease resistant. However, watch out for aphids, which can sometimes be a problem.
Support: Whorled milkweed usually does not need staking.
Invasiveness
Whorled milkweed can spread by rhizomes and self-seeding, but it is not considered invasive. It can form colonies over time.
Important Notes
Whorled milkweed is a vital host plant for monarch butterflies. Planting it in your garden helps support their populations.
All parts of the milkweed plant are toxic if ingested.
Whorled milkweed is deer-resistant.
