A late event in the King’s Copse Park Botanical Gardens has been long anticipated in the season now drawing to its close. Back in February I acquired what I thought were four Amorphophallus bulbifer tubers from different sources. Of those one turned out to be something else, another rotted and a third has produced only foliage in it’s first season. Now this one (pictured below) has belatedly lived up to its name.

The successes were both sourced from Himalayan Gardens of Forfar. A bulbifer is native to north-east India and the Himalayan region. It is described as amongst the hardiest of its genus, and also as being one of the easiest to grow. The bloom is said to reach around 40cm (16 inches) in height, and is followed by foliage up to a metre tall. It has been an ambition to cultivate this Aroid and bring one to bloom for some time and I’m pleased to have done so now. The flies it attracted (pictured below) seemed quite happy about that too, if a little confused about where the smell was coming from.

The mystery tuber referred to above, that came from a large Oxon garden centre, eventually revealed itself as Amo nepalensis (pictured below), a scarcer form in cultivation. This one is endemic to the eastern Himalayan region where it occurs at high altitude in India, Nepal, Bhutan and Bangladesh. Quite by chance given its accidental acquisition it became my Aroid of the year for 2020 in July … what an absolute stunner!

Amo nepalensis at King’s Copse Park BG (formerly known as Garsington’s shanty town)

Unfortunately when I un-potted the tuber later in the season it had partially rotted, having borne a fork scar on purchase but I took a chance with it anyway. I have read that Aroid tubers imported from Indian wholesalers (see here) can be of “mixed and unpredictable quality”, mainly due to bruising in transit. My experience so far of garden centre-sourced Amo and other Aroid tubers reflects this.

Amorphophallus (from the ancient Greek Amorphos “without form, misshapen”) is a genus of more than 230 tuberous Aroids, most of which are native to the tropical and sub-tropical zone of Asia. In these regions the plants are typically found in lowland forest margins and disturbed ground in clearings, but also in savannah grasslands. Several species occur in Africa, and a few more in Australia and some Polynesian islands, but “Amos” as I like to call them are not found in the Americas. Most species are endemic and many remain poorly understood and rarely cultivated despite their spectacular blooms.

Given the fleeting successes described above I looked into what else may be sourced and found British suppliers of two more varieties. Amo albus (pictured below) looks similar, superficially to nepalensis but with subtly different colouration. Also native to India and the Himalayas, it is said to be as easy to cultivate.

Amo konjak appears to be fairly popular amongst fellow Aroid freaks. Native to the south-east Asian and Far East region, this too is said to be one of the easier Amos to cultivate in British conditions and fully hardy. There are a number of videos on YouTube and I suspect the enthusiasts concerned must have grown their specimens from seed for several years for the sake of the brief flowering event, which does not especially appeal to me. The featured plants, also known as “Devil’s Tongue”, somehow looked less attractive than in these better pictures (below) I have seen.

Amo konjac (all images)

From sufficiently large tubers the tall dark-maroon inflorescence rises usually in spring, having a similarly toned erect spadix and strong foetid odour. The foliage emerges in early summer and grows rapidly. The stalk is mottled with pale pink and grey or olive-green and brownish spots, and is divided at the top to form a classic Amo structure resembling a canopy from which the leaves hang.

I acquired a growing plant on 19th August 2020 from Tropical Britain, and it was quite impressive to receive such a thing expertly packed and undamaged by mail order. According to the supplier’s information this should be watered and fed well until autumn then kept dry until November. When the foliage withers it is best to lift the tuber to avoid winter rot.

I am very pleased to have this plant that sold out within two days of my noticing stock had been released. Now months of gaining experience in cultivating the fascinating Aroids featured above lie ahead. These are long term projects, not instant gardening and that is what motivates me.

African and more SE Asian Amorphophalli 

These seven Amos (below) that are native to the African continent have especially caught my eye during this research. None of them appear to be available for private purchase in Europe at the present time, even if they might be cultivated here, but are they spectacular or what?

Amos (from top and left to right) abyssinicus, baumannii, consimilis, elliotii, johnsonii, dracontioides and aphyllus

Since I can’t get enough of all this here (below) are a few more from around the south-east Asian region. From left to right these are Amos dunnii (China, North Vietnam and Thailand), henryii (Taiwan) and prainii (Laos, Malaysia and Indonesia). If it was possible to acquire any of them for private cultivation I would leap at the chance.

The tubers of as many as 13 Amo species are said to be edible if prepared correctly and some are raised as cash crops within their home range. The aforementioned A konjac has long been used in China, Japan and south-east Asia as a food source and also as a traditional medicine. Low calorie, high fibre flour extracted from the corm is widely used to make noodles, tofu and snacks. Konjac noodles are known for an ability to suppress appetite since they cause the stomach to swell to create the feeling of being full.

A paeoniifolius or Elephant Foot Yam (pictured above) has been harvested in tropical Asia for centuries. Usually the tuber is cooked and eaten as a vegetable, and is often smashed with salt and eaten with rice. It is used widely in curries and also to make chutneys and other sweet dishes, and can be fried into chips. The young unopened leaves and young leaf stalks are also edible when cooked and are frequently served with fish.

In Indonesia these Yam tubers are the third most important carbohydrate source after rice and maize. They are also consumed widely in India and Sri Lanka, though elsewhere are regarded as a famine crop to be used when more popular crops such as rice are in short supply. 

Amorphophallus titanum

Last but by no means least herein is the world-famous phenomenon that is Amo titanum. Native to the Sumatran rain forest of Indonesia, this true giant amongst Amos is cited as boasting the plant kingdom’s bulkiest un-branched inflorescence, ranging from one to more than three metres in height and up to three metres in circumference. It has been in western cultivation since at least 1889 when one flowered at the UK’s Royal Botanic Gardens, Kew. Since then just over 570 more have been brought to bloom in cultivation around the world.

Blooming is infrequent and unpredictable and the foul-smelling inflorescence lasts for up to just 48 hours. It rises from a spherical tuber that is reputed to be the plant kingdom’s largest, weighing 70 kg or more. The spathe is the shape of an upturned bell with ribbed sides and a frilled edge, green speckled with cream on the outside and rich crimson on the inside.

The flowers are carried on the lower end of the greyish-yellow spadix. At the base, within the protective chamber formed by the spathe, is a band of cream male flowers above a ring of the larger pink female ones. When these are ready for pollination the spadix heats up and emits a stench that has given rise to the name ‘corpse flower’. The seed stalk (pictured below), that can reach up to two metres tall and holds large red berries, is equally impressive.

After the inflorescence dies back a single leaf emerges in its place, reaching the size of a small tree up to 7 metres tall and across. The leaf consists of a sturdy glossy green stalk mottled with cream, which divides into three at its apex and bears numerous leaflets. Each year, the leaf withers before a new one develops, using the tuber’s energy stores. When the plant is ready to flower again, the tuber becomes dormant for up to four months before another inflorescence emerges, growing upwards at a rate of some 10 cm per day.

Fruting Amo titanum at RBG Kew

This giant Aroid has proved very difficult to cultivate historically and there are only limited places in the world that do so. That is because it is prone to rotting, does not reliably increase in size and fails to produce seeds or offsets as easily as other Amo species. The plants rarely set seed because the female flowers open first and may no longer be receptive by the time the male florets are producing pollen. Even in the wild (pictured below) it is difficult because there must be an another similarly timed pollen producing inflorescence nearby. In addition, flowering can occur at any time of the year so chances are stacked against pollination.

At RBG Kew A titanum is catered for under high temperature and humidity in a tropical glasshouse, and kept in the shade. Even given optimum conditions the plant takes about six years to flower from seed. The first seed to reach Europe was returned from Indonesia to Italy in 1878. One of the young plants that germinated from them was subsequently dispatched to Kew, where it flowered in 1889, exciting great public interest. It next bloomed in 1901, and in 1926 the crowds attracted were so large that police were called to control them.

Kew now has multiple specimens, one or more of which can almost always be seen in leaf in the Princess of Wales Conservatory. But such is the unpredictable nature of the plant that the RBG cannot tell whether it will be months, years or even decades before a Titan Arum will next perform. But due to their burgeoning stock, more than three times as many have flowered there in recent years than over the previous century or more.

In 1996 one bloomed for the first time in many decades. Six years later there were an unprecedented three such events in as many months, the first evidence that Kew’s horticulturists had finally cracked the secrets of cultivating the plant. So between 2005 and 2009 there were up to three more flowerings each year, with the third of 2009’s being the largest ever measuring 2.48 metres. The most recent was in July 2019.

Amo titanum at (from left) Adelaide, Edinburgh and Rhode Island BGs

That increased success is being reflected at various other botanic facilities. Prior to the present millennium there were only 52 recorded flowerings worldwide, but the most recent published figure is just over 570. In the USA Juniper Level Botanic Gardens, NC which brought its first one to bloom on site in 2018, publishes a table of all known such events to date (see here).

Their retail nursery Plant Delights Inc claims to have sold over 1100 nursery propagated plants around the world and publishes a growing guide for private gardeners (see here). But this supplier counsels not to order them “unless you are a passionate and very serious Aroid nut”. Closer to home seed is available from a Dutch supplier (see here) who claims they are easy to germinate in perlite on a window sill. It would be interesting to know how many private collectors have succeeded with the Titan Arum, but I myself will give this one a miss!

All outsourced images in this post are © rights of owner reserved

Useful links 

A full list with pictures of validly described Amo species is published by the International Aroid Society see here.

In Europe the largest Amo collection of more than 150 species is maintained by Rareplants.eu, that offers seed of mostly dwarf species for sale.

The same source also publishes a cultivation guide (see here).