Literature: Der Palmengarten Vol. 58/1: 15-19

Aristolochia arborea: The Biology and Thread of a Remarkable Rain Forest Tree from Central America



Aristolochia arborea LINDEN is a small tree from the rain forests of central America. The thin corky stem branches freely and the entire plant grows probably up to 5-6 m. The leaves are entire and elliptical in shape. They are 25-30 cm long and 10-15 cm wide.

Only a very few specimens of this very attractive plant are in cultivation. The specimen at Bonn has been collected at the Botanic Garden Bogor by one of the authors (ROTH). A few specimens have been cultivated in Bogor since the beginning of this century (CAMMERLOHER 1922), and at least one plant has survived until the present day (see VOGEL 1978). There is nothing known about the origin of these plants. A specimen was already fully mature by the time of CAMMERLOHER. Therefore one can assume that this plant specimen belonged to LINDEN´s collection and probably represents type material.

Cuttings of the two plants at Bonn were sent to the Botanic Gardens Berlin, Frankfurt (Palmengarten), Hamburg and Munich. Aristolochia arborea is also in cultivation at the Royal Botanic Gardens Edinburgh, but the origin of this plant is unknown, too (R. KERBY, pers. com.). PFEIFER (1966) reports, that a person called BROADWAY has collected material from cultivated plants in Trinidad.

Due to the fast decline of central American rain forests and the fact that only few documented collections of Aristolochia arborea exist, one can assume that this species is extremely threatened.

The taxonomy of Aristolochia arborea

Aristolochia arborea was originally collected GHISBRECHT and a description appeared in 1858 in J.J. LINDEN'S. "Catalogue du plantes exotiques" (a the catalogue for exotic plants) for the price of

25 francs (~ 1£) (LINDEN 1858). Although this description was not very precise, some of LINDEN´s plants arrived at Kew and were later illustrated in Curtis Botanical Magazine (HOOKER 1862, Fig. 1). This article is therefore the first description in conjunction with that illustration.
Fig. 1: Illustration of Aristolochia arborea taken from: Curtis Botanical Magazine.

In his revision of the genus Aristolochia from north and central America, PFEIFER (1960) placed A. steyermarkii STANDLEY and A. salvadorensis STANDLEY into the synonymy of A. arborea. Having studied original descriptions of these species and living specimens of A. salvadorensis (obtained by H. W. WELTZ, BG Hamburg) the authors regard these species as clearly distinct. The very few locations of these three species are to be found in South-Mexico, Guatemala and El Salvador.

Based on the results of the systematic study on Aristolochiaceae HUBER (1960, 1985, 1993) divides Aristolochia into several genera. According to his findings A. arborea should be placed into the genus Isotrema, close to Isotrema (Aristolochia) tricaudata.

Flower Morphology and Pollination Biology:

The flowers of Aristolochia arborea appear at the base of the stem in short and branched inflorescences (Fig. 2). The perianth forms a flytrap, typical for Aristolochiaceae. The flower of A. arborea evolved uniquely showing the perfect imitation of a small toadstool in the centre of the brown perianth-tube (Fig. 3). Additionally the downward facing part of the perianth is white and resembles the mycelium of a fungus. This imitation reaches such a perfection that the toadstool can be identified as a member of the genus Marasmius. These fungi grow in the litter of tropical rain forests (G. KOST and F. OBERWINKLER, Tübingen pers. com.).
Fig. 2: Dense arrangement of flowers at the base of the stem 
Fig. 3: Single flower showing the imitation of a small toadstool
Although no field observations on the flower biology of Aristolochia arborea exist, it can be assumed that the flowers are pollinated by small sawflies (VOGEL 1978). On their search for a suitable place to deposit eggs, the females fall through a small opening into the flytrap. The upper end of the flower is equipped with a 'window' composed of some transparent cells. The insects desperately try to escape through them. During this process they continuously hit the sticky stigma and deposit some of the pollen brought in from other flowers. On the following day the anthers open and pollen is shed onto the flies. Afterwards the flower wilts and the flies can escape.

Until recently the few specimens of Aristolochia arborea grown at Botanic Gardens were propagated by means of cuttings. Therefore it is most likely that all cultivated plants are clones. There are no reports on any sexual propagation of the species. The reason for this may be found in an phenomenon, not yet understood: The flowers are protogynous. The three stigmatic lobes spread during the female stage and produce a wet stigmatic liquid. This liquid dries out and the stigmatic lobes close firmly together before the flower opens. This mechanism prevents a successful pollination under natural conditions and allows pollination only accidentally. At the time the flowers open, the anthers already shed the pollen. This phenomenon was already observed by CAMMERLOHER (1922), who opened flowers during the female stage and pollinated them artificially. During his research at Bogor BG he noticed that A. arborea produces fruits after self-pollination. However he does not report of seed germination nor on the results on any germinated off-spring.

Aristolochia arborea is a very rare and attractive species. The research conducted by CAMMERLOHER provided the base for hand pollination of the two specimen grown at Bonn BG.

Fruit Morphology and See Dispersal

A few days after pollination the two flowers dropped their perianth and the fruits grew very quickly. After 4-5 weeks they reached their final size. They were 12.5 cm (15 cm) long and 1.5 cm (2.5 cm) thick. The fruits were slightly curved, resembling a banana. In cross-section they were a hexagonal and had a shiny green colour, visible through reddish-brown hairs (Fig. 4).

5 to 6 months after pollination the fruits opened from the tip. The fruit splits into 6 parts which roll back, continously releasing approximately 60 seeds. After 10 days the seeds were released and the fruit decomposed totally (Fig. 5). The seeds are arranged in six rows densely packed and are heart-shaped. They are approximately 1 cm long and 0.8 cm wide and are embedded in a massive elaiosom. The elaiosom is twice the size of the seed. The seeds are collected by ants and carried away. Smaller ants carry the seeds away in a highly coordinated manner (Fig. 6).
Abb. 4: Fruit (final size), ca. 15 cm
Abb. 5: The fruit splits into 6 parts which roll back, continously releasing the seeds.
  Abb. 6: Seed with a massive elaiosom attracting ants
After 4-6 weeks 40% of the seeds germinated. The germinated seedlings are already plants of more than 1.5 m and flower regularly. Although they originated from self- pollination the plants show variability within the population: There are a few plants that do not produce any side shoots as the centre stem grows in height. Other plants branch freely and therefore remain small.

Having produced a nurnber of individuals by means of sexual reproduction one can expect the survival of this species at least under cultivated conditions. Seedlings were send at least to Amsterdam, Missouri, Kew (1995), Meise, Göteborg, Tübingen and Dresden. Hopefully Aristolochia arborea, as one of the most beautiful species in the genus, will not only been seen in Botanical Gardens.


The authors wish to thank Herrn G. Kost and F. OBERWINKLER (Tübingen) for the useful advice on the convergence of surface morphology of A. arborea and the fruit bodies of Marasmius species, Mr. H.W. Weltz (Hamburg) for the photographs and living material of A. salvadorensis and W. Lobin (BG Bonn) for his substatial help.


Cammerloher, H. (1922): Unfruchtbarkeit in Folge vorübergehender Kleistopetalie bei Aristolochia arborea. Ber. Dt. Bot. Bes. 40. 385-393.
Hooker, J.D. (1862): Aristolochia arborea. Curtis´s Bot. Mag. 88: Tab. 5295
Huber, H. (1960): Zur Abgrenzung der Gattung Aristolochia. Mitt. Bot. Staatssamml. München 3: 531-553.
Huber, H. (1985): Samenmerkmale und Gliederung der Aristolochiaceen. Bot. Jahrb. Syst. 107: 277-320.
Huber, H. (1993): Aristolochiaceae. In: K. Kubitzki, The Families and Genera of Vascular Plants, Vol. II, 129-137.
Linden, J.J. (1858): Catalogue des plantes exotiques nouvelles et rares, culiveés dans les cerres de J. Linden. 13: 6.
Pfeifer, H.W. (1966): Revision of the north and central American hexandrous species of Aristolochia (Aristolochiaceae). Ann. Miss. Bot. Gard. 53: 115-196
Vogel, S. (1978): Pilzmückenblumen als Pilzmimeten. Erster Teil. Flora 168: 329-366.

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