Blood flower (Asclepias curassavica) is a plant native to the American tropics of the Caribbean, Central America, and South America. Boasting stunning orange, yellow, and red flowers, blood flower is widely considered one of the most beautiful varieties of milkweed. Perennial in warmer climates, it is easily grown from seed as an annual in cold-winter zones. Medium-green lance-shaped leaves are arranged oppositely along 2- to 3-foot stems, topped with showy flower clusters in late spring into autumn. Also known as Mexican butterfly weed, this plant has been a popular choice for butterfly gardens, though recent research shows that it may have some adverse impact on Monarch butterflies.
Blood flower is usually planted by seeds sown directly in the garden or started indoors eight to 10 weeks before the last frost. It is a fast-growing plant that blooms about four months after the seeds sprout. Like other milkweeds, blood flower has a toxic milky sap containing cardiac glycosides that can be poisonous to humans and animals when ingested. Poisoning most often involves grazing animals, such as horses. Do not grow this plant around livestock pastures.
|Botanical Name||Asclepias curassavica|
|Common Name||Blood flower (bloodflower) tropical milkweed, Mexican butterfly weed|
|Plant Type||Herbaceous perennial, subshrub|
|Mature Size||3 ft. tall, 1–2 ft. wide|
|Sun Exposure||Full, partial|
|Soil pH||Slightly acidic to slightly alkaline (6.1–7.5)|
|Bloom Time||Early summer to fall|
|Flower Color||Yellow, orange, red|
|Hardiness Zones||9–11 (USDA); grown as annuals elsewhere|
|Native Area||Caribbean, Central America, South America|
|Toxicity||Toxic to animals and people|
Recent research has shown the blood flower is a host for a parasite (Ophryocytis elektroscirrha) that can seriously weaken monarch butterfly populations. Further, this plant may be harmful to monarch butterfly migration patterns when grown in states with frost-free winters since the butterflies prefer to remain feeding on this plant rather than completing the migration. Ensure you are following all pruning recommendations for blood flower if you choose to grow it in warmer U.S. climates that are along established migration routes. Many authorities now recommend planting native milkweed species rather than blood flower.
Blood Flower Care
Blood flower is a low-maintenance plant that is very easy to grow. It will remain evergreen in zones 9 to 11, but readily grows as an annual in other regions. It generally grows well in any well-drained soil and in a full-sun location.
If protection of monarch butterfly populations is important to you, there are special pruning techniques you can use if you're intent on growing blood flower in your garden.
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.
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.
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.
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.
Blood flower does not require regular fertilizing as it prefers poor, nutrient-deficient soils well. If you are starting blood flowers from seed, you may wish to fertilize the seedlings once they have become established to give them a boost at the beginning of the growing season, but this is not necessary.
Types of Blood Flower
The pure species of this plant has red-orange flowers with yellow hoods and grows to about 3 feet tall. Various cultivars of Asclepias curassavica have been developed to improve the flower color and create shorter, more manageable plants.
- 'Silky Gold' features large clusters of golden-yellow flowers.
- ‘Silky Deep Red’ is a cultivar with strong red flowers.
- ‘Red Butterfly' is another red option, featuring flowers that are darker red.
- ‘Apollo Orange’ is a cultivar with pure orange flowers.
- ‘Apollo Yellow’ has pure yellow blossoms.
Due to the fact that blood flower can interfere in the natural migratory pattern of monarch butterflies, it's best if they are not allowed to go to seed and spread, especially when grown in states without harsh winters to kill them off. Cut back the plants at ground level in the fall to ensure they don’t go to seed. When grown in areas with mild winters, blood flower should be cut back every couple of weeks to ensure it does not flower year-round.
Propagating Blood Flower
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 Blood Flower 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.
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 Blood Flower
Blood flower is a fairly easy plant to grow in containers, and because it is evergreen in warm climates, potted plants are sometimes moved back and forth between indoor and outdoor locations with the changes in season. When moved indoors for the winter, these plants will need the sunniest location you can offer.
Use a fairly large, deep container to provide room for the deep taproot, and fill it with ordinary commercial potting mix, preferably mixed with some extra perlite or vermiculite to improve drainage. Plants will need to be watered somewhat more frequently when grown in containers.
Common Pests and Plant Diseases
Pests are more likely to be problematic in warmer regions where 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.
How to Get Blood Flower to Bloom
This plant usually blooms from late spring into fall, though seeds direct-sown in the spring may not bloom until late in the summer. To extend the bloom period, start seeds indoors eight to 10 weeks before the last frost date.
Shady conditions may hinder flower development. Soil that is too rich or overfertilized can have the same effect—these plants thrive in poor soils.
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.
How is this plant used in the landscape?
Blood flower works well as an addition to perennial borders, cottage gardens, and meadow gardens. Its thin, open growth habit looks best if the plant is mixed with other tall species with an informal growth habit, such as other milkweeds, coneflowers, asters, Liatris, and ornamental grasses. This plant has been a common choice for butterfly gardens, as well, though many authorities now prefer other native species of milkweed
Are there better milkweeds to use if I'm concerned about monarch butterfly populations?
It is always best to select a Asclepias species that is a native plant in your region, as these are always well-suited to native butterfly populations. There are many such plant species that are native to North America, including:
- Asclepias speciosa (showy milkweed) is found in much of Western North America. It is hardy in zones 3 to 9.
- Asclepias verticillata (whorled milkweed) is found throughout the U.S. and is hardy in zones 4 to 9. Though not especially showy, it is a monarch butterfly magnet.
- Asclepias purpurascens (purple milkweed) is a pretty, though weedy, species native to eastern North America. It is hardy in zones 3 to 8.
- Asclepias tuberosa (butterfly weed) is a very popular garden plant with orange to yellow flowers. Many cultivars are available. It is hardy in zones 4 to 9.
- Asclepias incarnata (swamp milkweed) is a white-flowered species native to damp, boggy areas of the central U.S. It is hardy in zones 3 to 9; several cultivars are available.
Isn't milkweed edible?
Not a good idea. Although milkweed has been used in a variety of folk remedies, and despite the fact that online sources sometimes print information with "recipes" that supposedly render milkweed safe to eat, this is a very bad idea. Ingesting milkweed in any form comes with serious risks, including possible seizures and potentially fatal heart arrhythmias. Fortunately, this is only a problem if you eat the plant. While the sap can cause skin irritation, milkweed isn't a life-threatening plant unless you eat it.
Satterfield, Dara A., et al. Migratory Monarchs That Encounter Resident Monarchs Show Life-History Differences and Higher Rates of Parasite Infection. Ecology Letters, vol. 21, no. 11, 2018, pp. 1670-1680. doi:10.1111/ele.13144