If you are looking to attract butterflies to your garden or yard, the bloodflower is one of the best ways to do it. This plant is known for its ability to attract butterflies with the yellow, red, and orange flowers that bloom on its tall stems in the summer and fall.
I. Appearance and Characteristics
Asclepias curassavica, commonly known as tropical milkweed, is a flowering plant species of the milkweed genus, Asclepias. Other common names include bloodflower or blood flower, cotton bush, hierba de la cucaracha, Mexican butterfly weed, redhead, scarlet milkweed, and wild ipecacuanha.
Asclepias curassavica is described by NatureServe as a “widespread species, ranging from southern North America through Central America and into South America.”
It is an introduced species in the US states of California, Florida, Hawaii, Louisiana, Tennessee, and Texas, as well as the US unincorporated territories of Puerto Rico and the United States Virgin Islands.
It has been introduced and naturalized in the Chinese provinces of Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Qinghai, Sichuan, Xizang, Yunnan, and Zhejiang, as well as in Taiwan.
Asclepias curassavica was introduced to Australia prior to 1869 and is widespread in parts of Queensland. It is considered an exotic plant, and a weed, at the Meteor Downs South Project near Rolleston, Queensland, Australia.
Typical plants are evergreen perennial subshrubs that grow up to 1 m (3.3 ft) tall and have pale gray stems. The leaves are arranged oppositely on the stems and are lanceolate or oblong-lanceolate shaped ending in acuminate or acute tips. Like other members of the genus, the sap is milky. The flowers are in cymes with 10-20 flowers each. They have purple or red corollas and corona lobes that are yellow or orange. Flowering occurs nearly year-round. The 5–10 cm (2.0–3.9 in) long, fusiform shaped fruits are called follicles. The follicles contain tan to brown seeds that are ovate in shape and 6–7 mm (0.24–0.28 in) long. The flat seeds have silky hairs that allow the seeds to float on air currents when the pod-like follicles dehisce (split open).
II. How to Grow and Care
Sunlight
Blood flower grows best in full sun but can tolerate partial shade when grown outdoors. When choosing a spot in your garden for blood flower, select a location that receives plenty of direct sunlight throughout the day. When potted plants are moved indoors, they demand a very sunny location.
Temperature and Humidity
In most areas, blood flower is treated as an annual, although they are evergreen perennials in tropical climates—zones 9 to 11. Blood flower can tolerate both humid and dry environments but thrives in humid climates, such as the coastal areas of the deep south and southeast.
Watering
Blood flower is considered drought-tolerant but will do best when consistent moisture is provided. Supplement regular rainfall with occasional watering if you notice that the plant is drying out significantly between rainfalls.
Soil
Blood flower is able to grow in a variety of different soil types and generally isn’ picky about where it grows. Above all else, make certain that well-drained soil is provided, as blood flower does not like to be waterlogged.
Fertilizing
Bloodflower does not require much fertilizer, so doesn’t need to be fertilized often. After flower buds appear, a little phosphate fertilizer ensures growth during the flowering period. Apply organic fertilizer once before winter. This will increase the plant’s ability to withstand the harsh environment and survive the season. During dormancy, the physiological activities of bloodflower will slow down or even stop. Overfertilization causes excessive accumulation of nutrients, which leads to root rot. Hence, stop fertilization after the plant enters winter dormancy.
Planting Instructions
Plant it in spring after all danger of frost has passed. Tropical milkweed has a taproot and the younger the plant, the better it will tolerate transplanting. Dig a hole about twice the diameter of the nursery pot and about the same depth. Place the plant in the hole and fill in original soil to the top of the root ball. Gently tamp down the soil and water it well. Keep it watered for at least one week, or until the plant has visibly grown.
Space plants 2 to 3 feet apart.
Pruning
Pinching the young plants to encourage branching with more flower clusters is optional. What is not optional, however, is cutting down the plants to the ground in the fall if they don’t die on their own from the frost. Because if the plant remains alive, monarch butterflies will continue to feed on it instead of migrating south, a disruption of the natural cycle that is fatal for this endangered butterfly species.
Propagation
Vegetative propagation through stem cuttings is fairly easy with this plant, though it’s not commonly done since the seeds germinate and sprout so easily. However, the vegetative method may be the best option if you are growing one of the named cultivars and want to ensure an exact duplicate of the parent plant:
- During a period of active growth, snip a 6- to 8-inch long tip off a growing shoot, preferably without flowers or buds. Take care not to touch the milky sap, as this can cause skin irritation.
- Strip off the lower leaves, then plant the cutting in a small pot filled with commercial potting mix.
- Place in a bright, warm location and keep the potting moist until the cutting develops roots and new growth is evident.
- Once roots are established, the cutting can be transplanted into the garden. Don’t wait too long, as the plant will not transplant well once it develops a sizable tap root.
- Pinching back young plants will cause them to be bushier and produce more flowers.
How to Grow from Seed
For spring planting, start the seeds indoors eight to 10 weeks before the last frost. You can use commercial seeds or seeds collected from the mature seed pods of garden plants. Soak the seeds for 24 hours before planting, then sow them in small pots filled with seed starter mix or ordinary potting soil, and keep them in a bright, room-temperature location until they germinate. This normally takes two to three weeks. The seedlings can then be moved to a sunny location and kept moist (but not wet) until planting time. Seedlings transplant fairly easily, but established plants develop a long taproot that makes transplanting a tricky matter.
This plant self-seeds very readily, and volunteer seedlings can easily be dug up and transplanted into other areas in the garden.
Overwintering
When grown as a perennial in its established hardiness range, this plant requires no special winter protection. In colder zones where it is grown as an annual, mature plants should be cut off or pulled from the ground and discarded before they set seed.
Potting and Repotting
Tropical milkweed adapts well to container-growing, as long as you plant it in a tall 1-gallon container to fit its taproot. Choose a container with large drainage holes and fill it with a well-draining potting mix. Keep in mind that container plants require more frequent watering and fertilization than plants in the landscape.
Repotting of annual tropical milkweed won’t be necessary.
Even if your winters are mild and the plant remains green, don’t leave it outdoors. Either cut it back to the base or bring it inside for the winter where monarch butterflies cannot feed on it.
Pests and Diseases
Common Pests and Plant Diseases
Pests are more likely to be problematic in warmer regions where the blood flower grows as a perennial. In these regions, aphids often colonize on the leaves and stems, sometimes leading to sooty mold that develops on the honeydew excretions of the aphids. Aphids are best handled by simply spraying the plants with strong blasts of water to dislodge the insects. Avoid pesticides, as these are likely to also kill the desirable butterflies and their larvae, as well as other pollinators.
Pests are less troublesome in colder climates where the plants die back each winter.
Common Problems With Blood Flower
The complaint most often voiced with blood flower is the excessive self-seeding and rampant spread that can occur. This can be avoided by clipping off the developing seed pods before they can dry and break open to spread seeds on the wind. Though not considered invasive, blood flower can be annoying in its eagerness to produce volunteer plants in the garden.
Plants growing in shady conditions sometimes develop long, leggy stems that may collapse unless they are staked upright. This is rarely a problem for plants growing in full sun.
III. Types of Tropical Milkweed
- Silky Gold Tropical Milkweed
Asclepias curassavica ‘Silky Gold’ has large clusters of golden yellow flowers and yellow-green foliage. It reaches 3 to 4 feet in height and 2 to 3 feet in width.
- Silky Deep Red Tropical Milkweed
The deep red flowers of Asclepias curassavica ‘Silky Deep Red’ have tips that are bright yellow. It grows 3 to 4 feet tall and 2 to 3 feet wide.
- Red Butterflies Tropical Milkweed
Asclepias curassavica ‘Red Butterflies’ has clusters of scarlet-red and yellow flowers. It is slightly smaller than the other cultivars, growing 3 feet tall and 2 feet wide.
III. Uses and Benefits
Bloodflower is a plant that is grown ornamentally mainly for its showy red and orange flowers and year-round foliage. These flowers attract butterflies and hummingbirds to gardens in summer and fall. The best way to grow this subtropical plant is around patios or in containers. Good partners for this plant’s bright flowers are black-eyed Susans, lilies, and yarrow.
