Blue-flowered Milkweed for Pollinators
Tweedia caerulea: Blue milkweed, Star of the argentine, Southern star (Oxypetalum caeruleum is old botanical name)
- Perennial: USDA hardiness zones 10-11 (lows -1.1 °C or 30 °F)
- Annual in colder zones with overwintering
- Full sun to part shade
- Height: 2 to 3 feet- in perennial regions can vine up to 10 feet with support
- Spacing: 2-3 feet
- Flowers: blue with specks of dark purple
- Long, fuzzy, heart-shaped leaves
- Long summer bloom period
- Attracts bees and smallinators
- Grows well in Containers
- Blue-flowered milkweed- the only one!
- Leaves turn beautiful deep red in fall
- Not enough data from North America growers – monitor for potential issues
- Prone to get late-season milkweed bugs like most milkweed varieties
- Not a preferred host or nectar plant for monarchs
- Our monarch caterpillar hatchlings refused to eat it
Plant Propagation Options:
- Start seeds in late summer and overwinter indoors
- Start seeds indoors 2 months before final frost OR
- Seed Starting- Use a traditional seed starting mix with peat moss, perlite, etc.
- Sow seeds after final frost in annual zones
- Sow seeds directly in perennial zones
- Soak seeds in warm water 24 hours before planting
- Use a heated seed mat for faster germination
- Propagate from softwood stem cuttings using rooting hormone
- Start seeds in water
Tweedia Caerulea Growing Tips:
- Overwinter in pots for annual zones. Cut back to about 12″ before bringing inside
- If you don’t want additional seedlings next spring, simply cut off the seed pods before they pop open or bind them shut with twist ties, rubber bands, or tie organza bags over the pods if you want to collect milkweed tree seeds. Seeding is not an issue in annual zones.
I’ve seen no monarch activity in our northern garden, but a wayward tussock moth caterpillar scarfed down an entire tweedia caerulea stalk last season. Other pollinators that frequently sip nectar from the flowers: bumble bees, cabbage white butterflies, sweat bees, red admiral butterflies.
If you’ve seen other wildlife activity on your blue milkweed, please share your experience in a comment below…