Calotropis is a genus of shrubs commonly referred to as milkweed because of the latex substance discharged by the plant. Native to parts of Africa and Asia, this plant is considered a weed in many places.
Calotropis is a poisonous, flowering plant commonly found on neglected farmland.
The two most common forms are known as Calotropis procera and Calotropis gigantea.
Calotropis was first classified as a genus in the early 1800s. Calotropis gigantea is native to parts of Asia and North Africa. It is sometimes known as the crown flower.
Due to its potential toxicity, latex extract from both C. gigantea and C. procera was used as arrow poisons in Africa and folk medicine in India.
Plants in this family are commonly referred to as dogbanes because some species (such as Calotropis gigantea) were used as poison for dogs.
|Scientific name||Calotropis proceraCalotropis gigantea|
|Common names||Milkweed, Apple of Sodom, madar, Crown flower, calotrope, swallow-wort|
|Height||C. gigantea up to 10 feet (3m)C. procera up to 6 feet (1.8 m)|
|Width||6 to 9 feet (1.8 m to 2.7 m)|
|USDA Plant Hardiness Zone||USDA zones 10 to 11|
|Native to||Asia and North Africa|
|Blooming season||Throughout the year|
|Flower colors||Purple, white|
|Plant specific features||Contains a toxic, milky latex|
How to Plant and Grow a Calotropis
Where to Plant
In the wild, this is a weed that grows on abandoned farmland, and wasteland. It will grow up to and over 1000 m throughout India. It will grow on land where nothing else will survive. Frequently, it grows on disturbed, sandy, and dry soils.
It will tolerate saline, so can be useful if you have a coastal garden with salty soil, although it won’t tolerate strong sea winds.
Because milkweed grows rather aggressively, it might not be suitable for a limited space. It becomes rather weedy in appearance, so if you have sufficient sunshine, consider planting it at the back of a border to prevent it from taking over and getting out of hand.
When to Plant
If you are growing from seed, then set the seeds in trays indoors about two months before the final expected frost. A heat mat will speed up germination.
Alternatively, if you wish to sow direct, then wait until the last frost.
If you are planting a milkweed that has grown from a cutting taken in the summer, then you can plant this out in the fall.
Calotropis Shrubs Care and Maintenance
Idea soil for milkweed is that which has been disturbed, such as former farmland. Sandy light soil, without much rainfall, is great. Calotropis will grow in many types of soil, but it needs to be free draining.
PH levels aren’t too important, but the shrub does have a slight preference for alkaline. It will even tolerate salty soil.
Established milkweed doesn’t like too much water. In particular, the plant mustn’t be left to stand on wet ground. The risk of overwatering is more pronounced if you are growing the milkweed in a container.
Allow the soil to dry out between waterings. This is a plant that grows in dry soil, and once established is drought tolerant.
If you give your plant some slow-release fertilizer in the Autumn, this will encourage plenty of dense new growth. This is a plant that attracts the endangered monarch butterfly. It is important that any fertilizer used is organic so that it won’t harm wildlife.
Mostly, milkweed needs full sun to perform at its best. In the wild, in their native habitat, they are found in exposed, sunny sites.
Without sufficient sun, they will not produce sufficient flowers to attract the butterflies.
Pruning and Repotting
It’s a good idea to cut back your Calotropis once a year. This, coupled with the removal of diseased growth, will help to keep the plant healthy.
It will remove any fungus spores and, if you keep the plant clear of vegetative debris around the base, will minimize the risk of disease.
There are several ways in which to propagate milkweed. You can collect the seeds and plant them to germinate indoors in late winter. You will need to provide winter protection to give them the best chance of survival and possible flowering the following summer.
Or, you can plant them directly into the ground if you wait until after the last frost. It’s a good idea to soak the seeds for a day before you plant them.
This will speed up the germination process. It’s possible that the seedlings will not flower in their first year after planting.
Alternatively, propagate the milkweed by taking stem cuttings in the Spring. You will have larger plants quicker this way. The cuttings should be taken from the current season’s new growth. These are referred to as softwood cuttings.
Cuttings root very quickly – sometimes in just three days! If the plant from which you take your cutting is mature, then you can expect it to flower the first year after planting.
Pests and diseases
Always remember that milkweed is a toxic plant. Take care when touching any part of the plant and don’t ingest it or touch your skin after handling.
Prevention is better than cure. If you can keep your milkweed healthy, you will have little need to treat against disease. This will benefit the butterflies and wildlife that the milkweed hosts.
Fungal diseases can set in after periods of wet weather or overwatering. The symptoms are usually yellowing or spotty leaves. Remove all diseased leaves that are spotty or discolored and either burn or discard them.
You don’t want to compost them, because that will become a breeding ground for the fungal spores and risk spreading the disease into the soil.
Fungus can also be caused by poor air circulation around the plant. You may need to thin out the plants or remove sections.
Water at the base of the plant, rather than from overhead, and if necessary spray with an organic fungicide to wash the spores away and stop them reproducing.
Spider mites can also be a problem. These are almost invisible to the naked eye as they are so tiny. Milkweed and Japanese beetles are additional threats to the health of the milkweed.
They can damage both foliage and flowers, so keep them under control. The best way to do this is to pick them off by hand.
You can put them into soapy water, or you can treat the ground around the plants with an organic insecticide.
Be very careful when applying any products to milkweed. It is a plant that is a magnet for endangered butterfly species, and products designed to kill harmful insects may also harm butterflies and caterpillars.
Temperature and Humidity
This plant is not frost tender and grows in the UK and USDA zones 9. In cooler regions, it can be grown as an annual and it will die off in the winter. But because it self-seeds relatively easily, you may be able to gather and keep the seeds to resow the following spring.
Other Uses for Calotropis
Although milkweed is commonly considered a weed, it does possess a lot of uses, making it a useful weed! It is an excellent choice for a butterfly garden, providing food for both the caterpillar and the butterfly.
In agriculture and forestry, it is a source of green manure and a soil conditioner.
This poisonous plant has been used in Indian medicine and its latex extract is used to make a hemp-like fiber which is called mander or mudar. This is used in rope making and also for carpets, fishing nets, and thread.
Its seeds are fluffy, and the fluff is used as a stuffing material for mattresses and pillows and also weaved into cloth.
Milkweed has been identified as a possible hydrocarbon crop due to its high latex content.
A fermented mix of salt and Calotropis is used in tanning, for the production of sheep or goat leather.
The root and bark are also used in folk medicine, despite the serious adverse effects that milkweed is known to cause. It is a dangerous plant to ingest, due to the chemicals contained within all parts.
These chemicals, especially if taken in high doses, can result in serious and life-threatening conditions.
There have been many incidences of Calotropis poisoning.
The leaves are also poisonous and used to make insecticide and mosquito repellents. Leaves from the C, procera are used in parts of Asia as an antidote for snake bites. Their leaves are used also to treat liver disease, inflammation, burns, and rheumatism.
Types of Calotropis You Can Grow
As already stated, there are two main varieties of Calotropis. C. gigantea and C. procera.
The main difference between these two species is size. C. gigantea (Giant milkweed) is a fast-growing perennial in zones 10 or 11 or an annual in colder zones with winter protection.
It will grow to over 10 feet (3.05 m) in warmer climes and has purple and white, slightly fragrant flowers. It will flower all season, and it is grown to attract monarch butterfly larvae.
C. procera also grows in USDA zones 9 to 11 as a perennial or as an annual in colder regions. Unlike the giant milkweed, this perennial has fragrant flowers and attracts monarch butterflies, not just caterpillars.
The caterpillar can pupate on the plant and the flowers continue throughout the season, providing butterflies with a constant source of nectar.
Milkweed will also attract hummingbirds and bees to your garden.
If you are creating a butterfly garden and have the warmth of milkweed, then this is a great option. An added plus, it is a bit different from the run-of-the-mill perennial plants, so will give you a fresh outlook.
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