A blood flower is a tender perennial plant with the botanical name of Asclepias curassavica that belongs to the Asclepediaceae, or milkweed, family. These plants are native to tropical areas in South America and will only survive outdoors in the warmest weather. As a result, they are often grown as annual plants or planted in containers so they can be brought indoors during winter. Other common names for these plants include butterfly weed, Mexican milkweed, scarlet milkweed, and swallow-wort. All types of milkweed plants are toxic, producing a sticky, milky sap within the stems and leaves which can be irritating to the skin.
In areas where the temperature does not drop below freezing, the blood flower can be planted in the ground. These tropical plants are evergreen in temperate areas, often growing to 4 feet (1.2 m) tall or more, and blooming throughout summer and into fall. The plants should be cut back to the ground periodically to increase bushiness and flower production.
The blood flower looks much like its cousin, the common milkweed, with clusters of small, fragrant flowers. The blood flower produces bright multicolored flowers, with red or orange outer petals and vivid yellow centers. When done blooming, long thin seedpods form which will split open as they dry. This releases seeds into the air, where they are carried far and wide by their little parachute-like tops.
All forms of milkweed are food sources for many types of butterfly caterpillars, most importantly the Monarch butterfly caterpillar. This is the only type of plant that these caterpillars will eat, and they have been known to completely defoliate them. Since many gardeners grow blood flower and other milkweed plants to attract butterflies, however, this isn’t usually seen as a problem. If the damaged plants are cut back severely, they will grow new leaves and quickly recover from the damage. Children as well as adults enjoy watching the colorful caterpillars as they grow and form their chrysalis on blood flower plants before turning into butterflies.
While the plants are poisonous, the flowers provide food for a number of different insect species which feed on the nectar. Hummingbirds are frequent visitors to the blood flower as well. These plants are very prone to harmful milkweed bugs, aphids, and spider mites, though they do not usually cause significant damage. Most other insects cannot tolerate the toxicity of the leaves.
These plants are easy to grow from seed, though they are fairly slow to mature. Seeds should be planted indoors at least six to eight weeks before they are to be planted outdoors or moved into planters. New plants can be propagated from leaf cuttings as well, though this can be difficult. Blood flower plants do not transplant or divide easily, as they have extremely long, tough tap roots; as a result, transplanting should be done while the plants are small.