HEART LEAF MILKWEED Asclepias cordifolia
Heart-leaf milkweed is a perennial that grows to a height of 0.3 to 0.6 m (1 to 2 ft), with dark red-purple flowers whose hoods are slightly elevated above the base of the corolla. The flower structure is unusual—it has five stamens fused into a column, with five circular attachments called 'hoods', and an anther head surrounding the large stigma at the flower's center. The fruit (photo at left) is a follicle with many flat seeds that have silky hairs which disperse easily in the wind. The large opposite leaves are cordate, or heart-shaped. The plant grows in open or d woodland, often on rocky slopes and in mixed coniferous forest. The milkweeds are named for the milky sap which exudes from the plant's stem.
It blooms from May to July.
Monarch butterfly caterpillars are commonly found on all the milkweeds, including the heart-leaf milkweed. Even after the caterpillar has metamorphosed into a butterfly, the alkaloids they ingest from the plant are retained in the butterfly, making it unpalatable to predators.
Seeds are rare and in limited supply.
Type: Hardy perennial
Height: 60-90 cm (24-36 in)
Location: Sun or part sun
Hardiness zones: 7-10
Bloom time: Mid summer to fall.
Seeds per pack: 3
Note: This plant species is known to have toxicity. Ingestion of these seeds or this plant can cause illness such as vomiting or diarrhea. This plant family is known to cause dermatitis in some individuals. The juice or sap of these seeds or this plant may cause a skin rash or irritation. The use of gloves when handling may be beneficial.
Germination: As with many perennial seeds, these seeds can benefit from a period of moist cold to help them grow. This is done by giving them a cold 'winter' period (artificial or natural), and then a warming to simulate 'spring', and time to grow! Here's how this can be done:
Obtain a planting container that has holes in the bottom for excess water to drain. Place the seeds just under the surface of your growing medium, and water. Place your container in a cold area (but not freezing, perhaps a refrigerator) for 4-6 weeks. Once the cold period is completed, place the container at room temperature for them to germinate. Be sure to keep the soil moist during this entire germination period. Seedlings will sprout a few weeks, or occasionally several months, after the warming period.
If you are planting your seeds in late winter or spring, these seeds can be planted outdoors while it is still cool out (once the ground is workable and unfrozen), to receive the cold period naturally in the garden.