聖誕紅 Pandanus tectorius
The poinsettia (Euphorbia pulcherrima), a beloved ornamental plant famous for its striking red and green foliage, is a member of the family Euphorbiaceae. Native to Mexico and Central America, it thrives in terrestrial habitats, particularly in temperate zones with mild, stable climates. In its native range, poinsettias are commonly found in tropical forests, naturally growing as shrubs or small trees that can reach heights of 0.5 to 4 meters. They prefer well-drained soils with moderate moisture and bright, indirect sunlight, flourishing at low to mid-elevations.
Historically, poinsettias have played a significant role in Mexican culture, being associated with traditional celebrations and valued by indigenous peoples for their use as natural dyes and medicinal remedies. However, the plant's sap contains latex, which can be mildly irritating to the skin and toxic if ingested, warranting cautious handling.
A notable characteristic of poinsettias is their sensitivity to photoperiods, making them a classic example of a short-day plant. The vibrant red coloration of the bracts, often mistaken for flowers, is triggered by shorter light periods. Reduced daylight hours stimulate hormonal changes in the plant, leading to the breakdown of chlorophyll and the production of anthocyanins, which cause the green bracts to turn red. This process is best supported by daytime temperatures of 18–24°C and nighttime temperatures of 15–18°C. If nighttime temperatures rise too high, it can inhibit the formation of the red color in the bracts.
Widely cultivated for decorative purposes, particularly during the holiday season, poinsettias bring festive charm to homes and gardens worldwide. Their adaptability to various environments has made them a global favorite, symbolizing celebration and warmth.
Scientific classification
Kingdom: 植物界 Plantae
Clade: Tracheophyta 維管束植物
Clade: Angiosperms 被子植物
Clade: Eudicots 真雙子葉植物
Clade: Rosids 薔薇類植物
Order: Malpighiales 金虎尾目
Family: Euphorbiaceae 大戟科
Genus: Euphorbia 大戟屬
Species: E. pulcherrima 聖誕紅
Characteristics
Taxonomic Group
Angiosperms
Growth Form
perennial shrub
Height/Length
0.5 - 4 m
E. pulcherrima in the NSYSU Campus
Morphology and Description
Root
• Fibrous roots (type of root system).
Fibrous roots
Stem
• The stem is upright and flexible, green when young, gradually turning pale brown and woody with age.
• It exhibits multiple branching, with each branch tip bearing bracts.
Leaf form
• Leaves are ovate, elliptical, or lanceolate, 15–20 cm long and 4–8 cm wide.
• The apex is sharp, the base is rounded or truncate.
• The leaf margin can be lobed, incised, or entire.
• The surface is glossy green on top, pale green underneath with a powdery appearance, both sides hairless.
Phyllotaxy
Phyllotaxy
• Leaves are arranged alternately (Alternate phyllotaxy).
Ovate
Inflorescence
• The inflorescence is a cyme.
• Each cyme contains both male and female flowers, with a single female flower surrounded by numerous male flowers.
• The bracts are brightly colored, resembling petals, and are usually red.
Cyme
Fruit
• The fruit is a capsule, triangular-round, 1.5–2 cm long, and about 1.5 cm in diameter, smooth and hairless.
• Seeds are small, ovate, or round, with a smooth or slightly textured surface, gray or brownish-gray in color.
Capsule
Buds of E. pulcherrima
New Leaves of E. pulcherrima
Bracts Changing Color on
E. pulcherrima