Welwitschia mirabilis (Tree tumbo, Tumboa, Welwitschia, Onion of the Desert)

Although Welwitschia mirabilis is classified as a gymnosperm, you would never think such just by looking at it. The Welwitschia grows only two leaves in its entire life time. This would be normally understandable if this type of plant lived for a very short amount of time, but the truth is quite the opposite. Growing in an arid area of southwestern Africa (specifically the Namib desert), the Welwitschia can live up to 1500 years. Mature specimens can survive in the desert primarily off of fog drip from a large”nearby” water source. The Welwitschia does well in warm temperatures, never going below 60 degrees Fahrenheit and when mid-day temperatures are at or slightly exceed 100 degrees Fahrenheit. These plants are thought to be a possible link between primitive plants and angiosperms.

Welwitschia mirabilis (Tree tumbo, Tumboa, Welwitschia, Onion of the Desert)
Deciduous: no (native to deserts of southwestern Africa)
Hardiness Zones: 9-11
Height: usually less than 1 meter, rarely 2 meters tall
Diameter: maximum of 30 meters wide
Growth Rate: slow, only growing a few millimiters during the late spring/early summer rain
Age: potentially live up to 1500 years old
Root System: very large taproot
Family: Welwitschiaceae
Subspecies: none found

Tolerates: drought (once established)
Problems (major): First year saplings are reliant on summer rain and fog from the sea. If the plant’s taproot is unable to find groundwater, the saplings rarely survive. Cold is fatal. Overwatering will often lead to fungal infections and rotting.
Problems (minor): The end of the leaves are usually torn
Poisonous: no

Soil requirements: clay or sand, needs good drainage to reduce the risk of fungal infections
Air Requirements: warm conditions, high humidity helps
Watering requirement: Saplings require watering every
Sun requirement: part shade to full sun (Do not increase or decrease significant amounts of light at one time; it will cause shock to the plant.)

Needles: none
Cones (male): longer, cylindrical, contains strands on pollen on the outside of the cone
Cones (female): pinker, more globose
Leaves: large, strap-shaped, worn and sometimes shredded at the ends due to harsh conditions
Flowers: none
Fruits: Pollinated female cones after 9 months of fertilization, these appear much greener, cylindrical, and longer than unfertilized female cones
Seeds require stratification: No, the seeds will only germinate when there is a large amount of rainfall (usually in spring). The seeds become mature after around 9 months of fertilization.
Monoecious or Dioecious: dioecious

Leaf shape: long, thick (similar to succulent “leaves”), curling and winding, strap-shaped, turning brittle and brown near the ends
Leaf size: The two leaves can grow up to 9 meters each.
Stem: The trunk is short, woody, and extends into the large taproot. It is sometimes known as the “caudex” or “crown”.
Flowering structure: Cones are produced.
Flowering frequency: Cone production occurs usually in summer.
Bulb/Corm: none

Notable characteristics:
The nectar of both male and female plants contain up to a 50% sugar concentration to attract insects (predicted by either beetles or wasps, it was uncertain which is the primary pollinator).

Mostly a specimen plant in the United States. Some residents of the plants’ native habitat consume the crown/base . The ends of the leaves serve as food and a water source for herbivores such an antelopes and rhinoceros.

Sources used:

Welwitschia_mirabilis_8 An adult male plant bearing cones

015966-01 A conservation-related sign next to a relatively young W. mirabilis

Welwitschia_mirabilis_2 A large specimen in its native habitat

Welwitschia_mirabilis_3 Fertilized female cones, the individual “disks” are the seeds

Welwitschia_mirabilis_4 A W. mirabilis sapling

Welwitschia_mirabilis_5 Two mature W. mirabilis plants

Welwitschia_mirabilis_6A close-up view of female cones

Welwitschia_mirabilis_7 A close-up view of male cones

Welwitschia_mirabilis A Welwitschia at the Missouri Botanical Garden from December 2012

I do not own the rights of these images; all credit goes to its original creator(s). The last image was taken by me, and is free for educational use as long as this site is referenced.



1 Comment

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One response to “Welwitschia mirabilis (Tree tumbo, Tumboa, Welwitschia, Onion of the Desert)

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