Mirabilis

The plant

Mirabilis jalapa is native to the tropical regions of America. It is the most commonly grown ornamental species of Mirabilis, and it is available in a range of colors. It is an erect herbaceous perennial that grows from a tuberous rootstock and can grow up to 60 cm tall. It has become widely naturalized as a weed in many countries from the temperate zone to the tropics.

The genus Mirabilis belongs to the family Nyctaginaceae and is known as the four-o'clocks or umbrellaworts. The genus has several dozen species of herbaceous plants, mostly found in the Americas.

Flowering and pollination

The flowers usually open from late afternoon or at dusk, between 4 and 8 o'clock, giving rise to one of the plant's common names. Each flower stays open for one night, and senescence develops after approximately 16 to 20 hours the following morning. The flowers are pollinated by hawk moths. Despite their appearance, the flowers are not formed from petals but are a pigmented modification of the calyx.

Scent chemistry

The scent consists mainly of the monoterpene (E)-β-ocimene, with additional compounds such as (Z)-3-hexenyl acetate and myrcene. Clearly detectable amounts of β-myrcene, (Z)-3-hexenyl acetate, (Z)-ocimene, (E)-epoxy-ocimene and benzyl benzoate were also found. Minor components include alloocimene, (Z)-3-hexenol and methyl salicylate.

The major compound (E)-β-ocimene reached its maximum emission between 1700 and 2000 and could be detected until 0200, but only at trace levels thereafter. The emission of (Z)-3-hexenyl acetate peaked later, between 2000 and 2300. The petaloid lobes of the limb are the site of (E)-β-ocimene release. The emission of scent peaks in the evening, matching flower opening and the activity of hawkmoth pollinators. Benzyl benzoate, one of the scent components, has a weak, sweet-balsamic odor.

Colors

A single flower can be plain yellow, red, magenta, pink, or white, or have a combination of sectors, flakes, and spots. In the yellow variety, flowers can gradually change to a dark pink colour as the plant matures, and white flowers can change to light violet.

Uses

The flowers are used in food colouring. An edible crimson dye is obtained from the flowers to color cakes and jellies. In herbal medicine, parts of the plant may be used as a diuretic, purgative, and for vulnerary (wound healing) purposes. The powdered seed is used as a cosmetic, but the seeds are considered poisonous. Flower extract can be used as a natural pH indicator in acid-base titration.

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