There aren’t many flowers you can consider as being true blue. One of those we can see as a sky blue is the Tweedia (twee-dee-uh) caerulea (see-roo-lee-uh). The synonym would be Oxypetalum (oks-ee-pet-al-um) caeruleum (see-roo-lee-um). This plant can be found under the common names of Southern Star, Blue Flowering Milkweed or just Tweedia.
The genus came from a botanist by the name of James Tweedie who traveled throughout South America and sent back plant material to his native Scotland in the mid-19th century.
The plant is considered a tropical tender perennial. This plant is native to Brazil and Uruguay. It is in the milkweed family. We can grow it here in the Tidewater Area of Virginia as an annual but further south it can be considered invasive. As an annual, it will attain a height and spread of 24 inches and will bloom from late spring until late fall.
This is a real eye catcher since you don’t see this shade of blue in commercially grown plant material. You also may have to hunt the Web for this beauty since it’s not found at every garden center.
The flowers are borne in clusters at the tips of the growing stems. Each flower measures one inch across and will have five ice blue petals, hence the star. The leaves are generally a narrow heart shape, two inches long with a gray-green velvet texture.
Tweedia prefers full sun to partial shade. It is drought tolerant and can be an excellent addition to xeriscaping. It has a minimal watering requirement, just don’t keep it wet or rot will set in.
Deadheading the spent blooms will promote continual flowering throughout the season. If you want to start some seeds for next year, you can leave a seed pod on the plant to mature. Once the flower drops and the seed pod starts to form, it will take a month for the seeds to ripen. When the boat-shaped pod starts to break open naturally, you can harvest the seeds.
If you are familiar with the common milkweed, you are aware that each seed matures on a white “puff.” The same applies for the Tweedia. The seeds can be successfully stored over winter for spring germination. You can direct sow the seeds in the spring after danger of frost or start indoors about six weeks before the last frost has passed.
This plant will fit well within a perennial or annual garden. I always suggest making groups of plantings for maximum color display. If you don’t have the availability of a flower bed, you can use hanging baskets or containers for the Tweedia. They will perform great individually or in combinations with other sun loving plants.
If you are wondering if this plant will attract Tweedy Birds, I don’t know but it will bring in the hummingbirds. Hummingbirds enjoy this plant all summer as well as the Monarch Butterfly. Monarchs will deposit their eggs on this plant. In a couple of weeks, you will see the larva of the butterfly emerge and start feeding on the leaves. They do very little damage to the plant but are fun to watch. If you have children or grand-children, let them watch the life cycle of this beauty. It gets them involved in our natural world. This is the real southern “Star” of the summer when it comes to blue.