Amorphophallus titanum

The Titan Arum in Bonn 1996

It is their rapid growth that makes titan arum inflorescences so especially fascinating. In 1996, the following measurements were taken on the plant flowering in May (Ittenbach et al. 1998):

The tuber, which weighed approximately 32 kg, was potted on 9th February 1996 and watered for the first time on 8th March 1996. The bud was first visible on 22nd March 1996, and measurements commenced on 15th April 1996. At this point, measured from the soil surface up, the bud was 40 cm tall and displayed a daily growth of 7 to 19 cm. On 6th May 1996, from 10 to 10:30 pm, a faint carrion smell was noticeable for the first time. On 8th May 1996, the spathe started to open at around 1 pm, and the inflorescence had reached its final height of 233 cm. Within 5 hours, the spathe opened fully, and during this time its diameter increased from 30 to 136 cm. On 12th May 1996 at around 6:30 pm, the inflorescence collapsed after only four days. When the spathe opened on 8th May 1996, the plant entered the female phase in the night, that is, its female flowers were ready for pollination. Pollen was only shed 24 hours later, on 9th May 1996, at 6 pm.

The infructescence

Die Titanenwurz 1996 in BonnWe collected pollen from this plant, and, three weeks later, a small titan arum with a smaller inflorescence came into flower. While the spathe of this plant opened, we heard about another plant which was in flower at the same time, at the Palm Garden in Frankfurt, but which had already entered its male phase. W were grateful to receive fresh pollen from the Frankfurt plant, which enabled us to pollinate our plant in Bonn both with fresh pollen from Frankfurt as well as with the frozen pollen of our plant which had flowered three weeks earlier.

Interestingly, neither its provenance nor the different methods of preparing the pollen had any influence on fertilisation. The infructescence developed fantastically, growing to1.12 m tall with a circumference of about 60 cm. Its berries were coloured bright orange and up to 4.9 cm long. The mature fruits were harvested on 10th December 1996 and on 12th February 1997, and sown a day later, that is, on 11th December 1996, and 13 February 1997, respectively. In total, we harvested 450 berries, of which 70% contained two seeds. We distributed 210 berries to other botanic gardens, such as the Palm Garden in Frankfurt, the Botanic Gardens in Berlin, Kunming (China), Leiden, Mainz, Nanking (China) and Munich, as well as Royal Botanic Gardens, Kew.

We sowed the remaining approx. 360 seeds; of these, 293 germinated in the long time span between 31st January and 23rd May 1997. In total, we sent more than 220 small tubers to 41 different gardens worldwide, such as Smith College, USA, the botanic gardens of Batumi (Georgia), Bogor (Indonesia), Irkutsk and Tver (Russia), Orotava (Tenerife), Beijing and Thiruvananthapuran (India). So far, this has only been done successfully once, in the Palm Garden in 1992. The plant which flowered here in 1937 was pollinated with its own immature pollen. It did produce an infructescence, however, its berries did not contain seeds (Koernicke 1938). Recently, such an attempt at self-pollination was successful at the botanic garden in Huntington, where the seedlings are growing well.

Cultivation requirements

Erfolgreiche Nachzucht: Michael Neumann mit seinen SchützlingenWe use a compost made up of 80% fertilised standard compost, 10% sand and 10% finely ground pumice. The base of the planting tub is filled with a thick layer of drainage. During the growth period, the soil is kept moist, but not too wet in order to prevent the tubers from rotting. As soon as the leaf has wilted, watering is discontinued. From March to October, fertilisers are given once a week, and from November to February every three weeks. Fertilising is also discontinued when the leaf starts showing a yellow colour. The temperature should be between 34°C and a minimum of 24°C. The optimum temperature is 26°C. Humidity should be at a relative 80 to 85%. Very warm and moist greenhouses have proven to be ideal locations for the plant, which needs a lot of light for growth. They need a light place, but from April to September they should still receive shade at lunchtime; in winter they should receive as much light as possible. Growth periods vary between 9 and 24 months, the dormant period in between (2 to 4 months) is irregular; it begins when the leaf has wilted and ends when new growth is visibly pushing out of the tuber.

During the dormant period, fungal infections can lead to rot on the tuber. The most important pests are nematodes and root lice. Nematodes are practically impossible to eliminate, which makes sterile conditions especially important. Root lice can be dealt with biologically, using Hypoaspis (predatory mites), or chemically with appropriate agents. If there are any areas of rot on the tuber, these need to be cut down to healthy tissue, and the wounds need to be treated with powdered coal.

Propagation

When mature, separate the seeds from the fruit; this is best done while the fruit is still fresh. Then sow them immediately. Place them about 5 mm deep into individual 9 cm pots, into the abovementioned soil, but in a pocket of sand. The position of the seed does not influence germination. Place the pots in a very light place and ensure that there is a temperature of 26°C; additionally heat the ground to 26°C. Keep moist, but not too wet. During the dormant period, small plants may still need a little watering in order to prevent their small pots from drying out completely.

Because of the difficulties of its cultivation and therefore its relative rarity, a flowering titan arum is always a special event. Some of these inflorescences, if they happened to be growing at a convenient time, were turned into world-wide media events. Regionally, however, many visitors can be attracted into the botanic gardens. Thus, in Bonn, the 1987 flowering attracted 10,000 visitors and the flowering in May 1996 attracted 20,000 visitors in the space of only a week. These figures show the high value that people place on botanic gardens and their exotic plants.

Contents

  1. Amorphophallus titanum
  2. Picture gallery: Inflorescences 1937-2006 in Bonn
  3. The Titan Arum in Bonn 1996
  4. The Titan Arum in Bonn 2000
  5. Picture gallery 2000
  6. The Titan Arum in Bonn 2003
  7. Picture Gallery 2003
  8. The Titan Arum in Bonn 2006
  9. Picture Gallery 2006
  10. Literature & Links
  11. Guinness-Certificate

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