Crown-of-Thorns – Euphorbia milii – Bucknell Biology Museum Greenhouse

Taxonomy

Common Name: Crown-of-Thorns

Botanical Name: Euphorbia milii Des Moul.

Synonyms: ^{1, 2}
Euphorbia bojeri Hook.(1836),
Tumalis bojeri (Hook.) Raf. (1838)

Family: Euphorbiaceae Juss.

Taxonomic Fun Facts:
This plant is named after the once governor of Bourbon Island (now known as the island of Réunion), Baron Milius, who is thought to have introduced the plant to France in 1821.⁴

Morphological Characteristics

Crown-of-thorns tends to be an evergreen shrubby or sprawling succulent with thick, waxy leaves. It is characterized by its grey, twiggy stems with long thorns and small, insignificant flowers (known as “cyathia”). The flowers are nestled in brightly colored modified leaves called bracts, which are often mistaken for flower petals and fulfill a similar purpose by attracting pollinators. The bracts are typically red, pink, or white, though there are also yellow and orange cultivars. The petalless flowers surrounded by bracts are characteristic of the family Euphorbiaceae.

Macro photo of an crown-of-thorns branch tip (also called an inflorescence) with yellow flowers. The branches are grey and highly thorned and the flowers are flanked by thin but succulent leaves. — Crown of Thorns Inflorescence

Diagram of crown of thorns showing the flowers, also known as cyathia, and bracts, which look like petals. — Crown of Thorns Diagram

A crown of thorns plant with no flowers. The plant is in a terracotta pot with a white brick wall backdrop. The branches are grey and highly thorned and full of thin but succulent leaves. — Crown of Thorns Plant Without Flowers

Some branches of crown-of-thorns with yellow flowers. The branches are grey and highly thorned and the flowers are flanked by thin but succulent leaves. — Crown of Thorns Plant with Flowers

Ecology, Distribution, and Use

Conservation Status: Least Concern³

Conservation Concern:
This plant is currently thought to be declining in its native environment due to habitat fragmentation and degradation.³

Geographical Range:
Crown-of-thorns is endemic (native) to the island of Madagascar. It can also be found on the African mainland, including Kenya, Tanzania, and Uganda, though these populations may be introduced. Introduced populations can also be found in Asia and South America.^{1, 4,}5, 6

Ecoregion: Madagascar spiny forests

Ecological Interactions:
In its native ecosystem, the fruits and flowers provide food for animals and pollinators, while thorny thickets provide habitat for birds and small animals. In areas where it is introduced, it can outcompete native species, leading to altered ecosystem function and loss of endemic biodiversity. ^{5, 6}

Ethnobotanical Use:
Crown-of-thorns is a widely grown ornamental species and can be found all around the globe due to its drought tolerance. It is also a beloved house plant. It also has traditional pharmacological use and has been used to treat inflammation, microbial infection, and promote wound healing. There is a body of research that is also looking at the plant’s latex and leaf extracts as possible agents for therapeutic applications against cancer. It should be noted that the latex of this plant is considered toxic if ingested and can act as a skin irritant in mammals.⁵

Crown-of-Thorns – Euphorbia milii

Taxonomy

Morphological Characteristics

Crown of Thorns Inflorescence

Crown of Thorns Flowers

Crown of Thorns Diagram

Crown of Thorns Plant Without Flowers

Crown of Thorns Plant with Flowers

Ecology, Distribution, and Use

Sources