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A giant blooms

Arno King

Arno King

February 27, 2012

Late in January this year a strange plant came into bloom in John and Genny’s nursery, located to the south of Brisbane. Known as the Titan flower, the

Titan flower, Amorphophallus titanum, in bud

Amorphophallus titanum – christened ‘Anastasia’ – produced a massive flower 2.1 metres high and 1.2 metres wide. The flowering of this plant is a very rare occurrence and causes a great commotion around the world – for this is the largest unbranched inflorescence or largest true flower in the world.

As far as I know, this is one of only two flowerings of this plant in the Australia. The other plant flowered in the Cairns Botanical Garden a month earlier. What is most notable about Anastasia is that she is growing in a shadehouse in a subtropical region.

Amorphophallus belongs to the Aroid family (Araceae) and has the typical Aroid flower with a skirt-like spathe (in this case reddish brown and fluted) and a spadix which rises high above it. Other well known aroids include Philodendron, Monstera, Aglaonema, Dieffenbachia, Alocasia and Colocasia. Many of these plants are popular house or garden plants and are known for their tenacity.

John with ‘Anastasia’, the Amorphophallus flower

Amorphophallus titanum is regarded as a highly tropical plant coming from the rainforests of western Sumatra and is generally only grown in the wet tropics or in heated greenhouses in subtropical and temperate zones. What is most notable is that the flower was a lot larger than many others recorded and that the flowering period lasted for 5 days, which is longer than many other reported flowerings. This can be attributed to the cultural conditions and the growers’ expertise.

Amorphophallus are cormous plants that produce an umbrella like leaf, generally during the warmer, wetter period of the year. During the drier, cooler period most species die down below the ground. Amorphophallus titanum generally produces its foliage in December and then dies down in June. When talking to growers in Cairns, John finds that there is generally a synchronicity, give or take a couple of weeks, between when his plant spurts into growth and dies down. The dormancy corresponds very much to the general rainfall in Brisbane, however John ensures that the plant is kept moist at all times during its growing period as his potting media drains readily. There is generally a torrential downpour every day at around 4pm in the plant’s habitat so it would never dry out in habitat. While dormant, Anastasia is left alone.

Rich red spathe surrounds the golden spadix

John attributes his success with this plant to providing it with a large enough container. When he examined photographs of other Titan Flowers flowering in cultivation he felt the pots were much too small and that the plants would dry out too readily between waterings. Anastasia grows in a 1000 litre water drum which has been lined with rice hull bags. The base of the drum has a drainage layer of polystyrene and then was filled with 300 to 400mm of potting media. A mound of potting media was built up in the middle of the pot, and the corm was placed on top of this. Finally the pot was backfilled with potting mix. John notes that most of the plants roots grow from the top of the corm.

John makes up his own potting media for all his plants. He finds that the commercially available potting medias generally break down within a year and the plants then start to decline. With so many plants in the nursery, John generally repots his plants every 5 years. His potting mix is based on University of California mix. He uses screened ash and peat and the mix is very free draining. John also makes up a balanced fertilizer containing a special mix of macro and micro elements which he adds to his mix. In particular he believes all tuberous plants benefit from additional soft rock phosphate (not superphosphate) in the media. He also believes in providing good levels of calcium and applies calcium chelates and finds this minimizes fungal and bacterial damage to the plants. Amorphophallus titanum comes from an area with visible limestone cliffs so there would be high levels of calcium in the soil and also in the decaying humus. Finally additional iron is added, in the form of iron chelates and GU49.

The underside of the huge spathe ‘skirt’

Plants are fed weekly and weakly with liquid fertilisers. These include seaweed, fish and a variety of other fertilizers which are rotated to provide a varied regime. Foliar feeding has not been possible with Anastasia, as her leaves grow to over 3 metres high.

Many species of Amorphophallus are renowned for the evil smell of rotting flesh that permeates from the flower. These species are pollinated by flies which are attracted by the promise of a good feed. Interestingly, no scent permeated from Anastasia’s interior.

John received the small tuber from Cairns 8 years ago, and understands it was 2 years old from seed. He has a keen interest in Amorphophallus and grows many other species propagating them from seed or leaf cuttings.

Anastasia became a media sensation while in flower, appearing on the TV news and in local and state newspapers. Streams of people came to see her in flower. Now the flower has collapsed and we will have to wait a few more years until she once again produces this astonishing flower. In the meantime she will still reign supreme in the shade house with her tree-like umbrella of foliage.

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