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Butterfly Gardening and Habitat Program

 
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Tropical Milkweed - Asclepias curassavica

Other common names for this plant include Scarlet Milkweed, Mexican Milkweed, Bloodflower, and Silkweed.

Technically not native to the United States, tropical milkweed is widely popular in butterfly gardens. Growing as a naturalized perennial plant in the southern U.S., it can also be easily started from seeds in the northern U.S. and treated as an annual. For an even longer blooming period in colder regions, tropical milkweed plants are easily potted up in the fall and grown indoors over the winter.

Blooming over a wide range of months (depending on location), many sources claim that tropical milkweed is the preferred milkweed for monarch caterpillars due to its tender leaves. Whether or not this is true, it is certain that tropical milkweed is a popular as both a caterpillar food plant and butterfly nectar plant.

The one problem that plagues the appearance of tropical milkweed in the garden are aphids. Lots and lots of aphids. Aphid control on outdoor plants may be as simple as spraying the plants with a burst of water from the hose which will dislodge the aphids (and which will have to be repeated all season). Generally, aphid infestations are a bit unsightly but do not impair blooming or plant growth.

A second problem that can impact the appearance of tropical milkweed is a result of the severe defoliation caused by Monarch and/or Queen caterpillars. This problem of course has the trade off of providing great caterpillar watching while helping to produce more butterflies. Once the plants are defoliated or the caterpillars have moved on, it is a simple matter of cutting back the tropical milkweed, which will resprout from the plant's base. Regrowth is fairly fast and the plant will rebloom.

Importance as a caterpillar food source: Like all milkweeds, tropical milkweed is a food source for the Monarch caterpillar. Queen caterpillars, which are found in the southern states, particularly Florida, southern costal areas, Texas, and the southwest, will use tropical milkweed as a food source. Additionally Soldier caterpillars, which are locally common to southern Florida and Texas, can be found on tropical milkweed.

Importance as a butterfly nectar source:
In addition to monarchs, tropical milkweed provides nectar for a wide variety of butterflies, pollinators, and hummingbirds.

The current rating for tropical milkweed is:

Caterpillar Rating
3
2
3

If you have experience growing tropical milkweed, we would like your opinion. Let us know how it performed in your butterfly garden. Your comments will help other butterfly gardeners in your region to create better butterfly gardens:

 

Tropical Milkweed Cultural Requirements
USDA Hardiness Zone 8B - 11, remains evergreen in 9B - 11, can be grown as annual in zones north of 8B
Bloom Period Continual bloom spring thru fall
Bloom Color Scarlet red, orange or yellow
Plant Height 36 to 48 inches
Plant Spread varies with age of plant
Light Exposure Sun to part shade
Soil Moisture Moist to average to dry
Animal/Disease Problems Deer resistant, aphids may be a problem
 

 

 
 

 

Tropical Milkweed


 

Naturalized Range for Tropical Milkweed (Asclepias curassavica)

 

Tropical Milkweed resprouting inside and aphid-free after cutting back to five inches in December in Zone 6 New Jersey

In temperate zones, instead of starting seeds indoors eight to ten weeks before the last spring frost, try repotting outdoor tropical milkweed plants the previous fall. They easily over winter as house plants and will bloom much earlier during the next growing season than plants started from seeds. Cut back outdoor plants and rinse well with water before bringing inside in order to lessen the chance of indoor aphids.

 

In climates where tropical milkweed is evergreen (that is, it is not killed by a frost or dies back to ground level over the winter), many butterfly gardeners choose to cut back their tropical milkweed plants to the ground once a year. This practice is thought to decrease the occurrence of Ophryocystis elektroscirrha, a protozoan parasite that is fatal to Monarch butterflies. Populations of this parasite may build up on the leaves of tropical milkweed when it is allowed to remain evergreen. By occasionally cutting back tropical milkweed plants, the spores of O. elektroscirrha are eliminated.

 

 
 
     

 

©2008 North American Butterfly Association