Southern Star

Oxypetalum caeruleum

Family: Asclepiadaceae (ass-kle-pee-ad-AY-see-ee) (Info)
Genus: Oxypetalum (oks-ee-PET-al-um) (Info)
Species: caeruleum (see-ROO-lee-um) (Info)
Synonym:Tweedia caerulea


Vines and Climbers

Foliage Color:


Bloom Characteristics:

Unknown - Tell us

Water Requirements:

Drought-tolerant; suitable for xeriscaping

Average Water Needs; Water regularly; do not overwater

Where to Grow:

Unknown - Tell us


12-18 in. (30-45 cm)

18-24 in. (45-60 cm)

24-36 in. (60-90 cm)

36-48 in. (90-120 cm)


15-18 in. (38-45 cm)

18-24 in. (45-60 cm)


USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

USDA Zone 10a: to -1.1 C (30 F)

USDA Zone 10b: to 1.7 C (35 F)

Sun Exposure:

Sun to Partial Shade


Unknown - Tell us

Bloom Color:

Light Blue


Bloom Time:

Late Spring/Early Summer

Mid Summer

Late Summer/Early Fall



Other details:

May be a noxious weed or invasive

Soil pH requirements:

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

7.6 to 7.8 (mildly alkaline)

Patent Information:


Propagation Methods:

From softwood cuttings

From seed; direct sow outdoors in fall

From seed; sow indoors before last frost

From seed; direct sow after last frost

Self-sows freely; deadhead if you do not want volunteer seedlings next season

Seed Collecting:

Allow pods to dry on plant; break open to collect seeds

Properly cleaned, seed can be successfully stored


This plant has been said to grow in the following regions:

Arroyo Grande, California

El Cajon, California

Encinitas, California

Fremont, California

Grass Valley, California

Long Beach, California

Los Angeles, California

Napa, California

Sacramento, California

San Diego, California

San Jose, California

Soledad, California

Vista, California

Deland, Florida

Navarre, Florida

Riverview, Florida

Snellville, Georgia

Battle Creek, Michigan

Elizabeth City, North Carolina

Trinity, North Carolina

Fair Play, South Carolina

Okatie, South Carolina

Austin, Texas

Garland, Texas

show all

Gardeners' Notes:


On Apr 29, 2014, Sandra13 from Sacramento, CA wrote:

I have this plant in my garden here in Sacramento. This is the second year and it's doing well. We had a few consecutive nights in the 20's last Winter but it survived. I have no complaints about this plant except for the orange aphids that it attracts. It grows more like a small shrub for me. Love the color! I'm happy I planted it.


On Nov 24, 2013, RosinaBloom from Waihi
New Zealand (Zone 1) wrote:

Southern Star has perhaps more of an upright, trailing or twining habit.


On Aug 8, 2013, Domehomedee from Arroyo Grande, CA (Zone 9a) wrote:

An Asclepia from South America. "Tweedia" is also called "blue milkweed". This was my first year growing this unusual diminutive plant, I say this because it remained under one foot tall. It did however bloom and seed, I have hopes it will survive the winter and get larger next year. I will be growing more of this as it has a true blue flower.


On Apr 27, 2011, zone10 from San Diego, CA (Zone 10b) wrote:

This plant has one of the most true blue flowers I've seen. It is a tough plant and very showy in the springtime. In my frost free zone, this plant stays green year round and flowers repeatedly over several of the warm months. Flowers are followed by large seed pods that break open to reveal silky threads attached to flat, dark, round, seeds. They are carried by the breezes and germinate very easily. Seeds seem to remain in the ground until the following rainy season. Since they are all volunteers, I don't make an effort to water these plants and they have proven to be extremely tolerant of drought and heat. Oxypetalum coeruleum grows beside my cactus and succulents. A great plant for many reasons!


On Sep 6, 2008, LoriPo from Battle Creek, MI wrote:

This is one of my favorites because the flower is such a beautiful blue. It will grow as an annual in this area, but it is hard to find a source that sells it locally. This last spring I was fortunate to be at my favorite retail greenhouse when an employee brought out two flats of Tweedia. I was so excited! I may attempt to grow my own from the seeds I have just in case I can't find the plants next spring.


On Mar 19, 2005, pokerboy from Canberra
Australia (Zone 8b) wrote:

This plant gives beautiful blue flowers during summer and autumn in my climate. It is followed by bizzare, fluffy seedpods. They have a very soft texture. It is a strange blue you often do not find other plants giving. pokerboy.


On Apr 29, 2004, martina from El Cajon, CA (Zone 10a) wrote:

Abundance of blooms of a very intersting lovely blue color and as a bonus somewhat bizarre seedpods afterwards. Fairly sturdy beautiful plant. My favorite.


On Aug 30, 2001, Terry from Murfreesboro, TN (Zone 7a) wrote:

Dainty flowers start out as pink buds, opening to lavender or blue. Can be overwintered in a greenhouse, or grown as an annual in colder climates.