Oxypetalum Coeruleum

Blue-flowered Tweedia Milkweed for Pollinators

Oxypetalum Coeruleum common names: Blue milkweed, Star of the argentine, Southern star, Tweedia caerulea

Tweedia caerulea is blue milkweed that supports garden pollinators including red admiral butterflies and bumble bees. Southern star is the only milkweed variety with true blue flowers.

Oxypetalum Coeruleum Plant Specs

  • Perennial: USDA hardiness zones 10-11 (lows -1.1 °C or 30 °F)
  • Annual in cool 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: pale blue flowers or turquoise blooms with specks of dark purple
  • Long, fuzzy, heart-shaped leaves
  • long, slender milkweed pods

Oxypetalum Coeruleum Pros

  • Long summer bloom period
  • drought-tolerant milkweed variety
  • Attracts bees and smallinators
  • Grows well in Containers
  • Blue-flowered milkweed- the only one!
  • Leaves turn beautiful deep red in fall
I was hoping this would be a good emergency milkweed variety for monarch caterpillars, but the two newly hatched monarchs I placed on fresh tweedia caerulea leaves crawled off quickly to seek out some real milkweed. While this is a good pollinator plant, I would not rely on it it to support munching monarch caterpillars...
Will Monarch Caterpillars Eat Blue Milkweed?

Oxypetalum Coeruleum Cons

  • 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 plant or nectar plant for monarchs, but used as a host plant by monarch butterflies in continuous-growing warm zones when other milkweed is unavailable
  • Our Minnesota monarch caterpillar hatchlings refused to eat it, but if eggs are deposited on tweedia plants, baby caterpillars will eat, grow, and thrive:
If mama monarch lays eggs on the plants, monarch caterpillars can grow and thrive on tweedia. More photos and info...
Photo Courtesy of Ginny Spurlock in Lake Oconee, Ga.

Tweedia Milkweed Plant Propagation Methods

Blue Milkweed can be grown as an annual in North American gardens and will flower and seed its first season. More info and photos...
Tweedia is a milkweed variety with brilliant blue flowers. The warm weather milkweed can be propagated several ways, including placing the seeds directly in water.

Tweedia Milkweed 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 bagsir?t=monabuttgard 20&l=ur2&o=1 tweedia caerulea over the pods if you want to collect  milkweed tree seeds. Seeding is not an issue in annual zones.
Tweedia caerulea seeds are ready to harvest when the pod seam splits open, revealing the dark brown milkweed seeds.
Tweedia Treasure

Pollinator Plus

Bumble bees are regular visitors to Tweedia caerulea. The blue milkweed flowers have proven to be one of their surprise favorite nectar sources.
Buzzing Over Blue Milkweed

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…

Buy Tweedia Milkweed Seeds and Plants

While tweedia is easier to say and spell, purchase plants and blue tweedia seeds that are labeled by the botanical or scientific name, Oxypetalum coeruleum to avoid purchasing the wrong plant:

  1. Buy Tweedia Milkweed Seeds Here
  2. Find Tweedia Seeds on Etsy

25+ Milkweed Varieties to Attract and Support More Monarchs

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4 Comments

  1. Hello Tony
    I went out yesterday on a flower mission and found a plant that looks almost like the one pictured here, the leaves look like Swamp Milk Weed, it is about 18″ tall with Blue Flowers.there was a Monarch and a Swallow Tail on another plant near by .
    You mentioned Hardiness Zone 10 and 11, I live in Zone 7, could it be the same plant?
    The flowers on the plant I found are a little darker blue.
    Regards Cliff

    1. Hi Cliff, if you’re in zone 7 it’s doubtful. Compare to the photos here and find more photos by searching google images, or post a photo on the facebook page: Monarch Butterfly Garden

  2. I had a Monarch caterpillar feasting on bluestar in Anaheim California and there were tropical milkweed, California narrowleaf, pineneedle milkweed and various California desert milkweeds in the yard as well.

  3. I’m in Southern Ca and have had Monarch feeding on this plant.

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