Warsaw/ The world's smelliest flower will bloom in the botanical garden

In early August, the smelliest flower, the giant arum, will bloom for the second time in Warsaw's Botanical Garden. It blooms extremely rarely and for a very short time, attracting crowds of observers. Its curator remarked that this plant can be described as "three times the best."

The blooming of this unique plant is always witnessed by thousands of fans, some traveling hundreds of kilometers to witness the event. Botanical gardens where the arum blooms are hosting special online broadcasts where you can watch the spectacle 24 hours a day.

The Warsaw Arum is growing in the tropical greenhouse of the University of Warsaw Botanical Garden. For those unable to watch the event live, the garden has prepared a live stream.

The giant arum belongs to the Araceae family and is native to the equatorial forests of Sumatra. It produces an inflorescence that can reach three meters in height and over 1.5 meters in width. The inflorescence and leaf grow from a hidden underground tuber weighing up to several dozen kilograms. The inflorescence is open for only two days, so its fragrance spreads over long distances to attract as many pollinators as possible.

"It's a plant three times the largest. It has the largest inflorescence, the largest leaf among the species of the genus Amorphophallus (arum), and the largest underground organ, which is the tuber," Piotr Dobrzyński, curator of the greenhouse plant collection and caretaker of the Warsaw arum, told PAP.

In Warsaw, the arum lily is cultivated in the greenhouses of the University of Warsaw Botanical Garden. It first bloomed in June 2021, generating great interest. Our experts predict that this year it will bloom between August 4th and 10th, but it all depends on the temperature.

The 2021 inflorescence measured 125 centimeters. On Tuesday morning, it was already 158 cm tall, making it significantly taller than the previous one. It grows about 8 centimeters per day.

"The inflorescence contains female flowers (pistils in the lower part) and male flowers (stamens in the band above the pistils). There are a lot of them, over 400 in total. The female flowers open before the male flowers to prevent self-pollination," said Piotr Dobrzyński, MSc., who cares for the plant.

He explained that a characteristic feature of this plant is that its inflorescence emits a rather distinctive scent, the intensity of which varies daily. It gradually increases from late evening to midnight, when its pollinators, such as carrion beetles and flies, reach their peak activity, and then subsides.

"Analyses of the chemicals released by the inflorescence have shown that it is a mixture of many aromatic compounds reminiscent of cheese, garlic, rotting fish, sweaty socks, the sweet scent of flowers, phenol, and indole, typical of feces. Its odor is often described as the smell of rotting meat—it's one of the plant's clever strategies for attracting pollinators," Dobrzyński said.

He added that the smell reminded him of ammonia and made his eyes water. He noted that the smell was noticeable from the moment he entered the greenhouse.

"It's hard to say whether it will be the same this time. Everything will become clear once the inflorescence opens," he said.

He emphasized that the third strategy for attracting pollinators is the appearance of the sheath surrounding the inflorescence. This sheath is reddish-brown in color and plays an important role on the second day of flowering.

– The specific color attracts insects that think it is bloody meat that can provide food for their larvae and they fly from the most remote parts of the forest to lay eggs – noted the botanist.

During the first phase of flowering, which occurs at night, female flowers are ready for pollination. In the second phase, which occurs on the second day, male flowers release pollen, although the female flowers are no longer receptive to pollination.

– This carefully planned arrangement helps ensure cross-pollination, meaning that fertilization will only be possible between different plant individuals, thus preventing self-pollination – said Dobrzyński.

He noted that if pollination does not occur, the inflorescence dies completely and falls off the tuber.

"If pollination occurs, fruits develop, which turn bright red when ripe. Each individual fruit contains a single seed. The infructescence takes on a shape similar to a corn cob," he added.

Currently, several specimens of the Arum lily are blooming simultaneously in Europe.

– Even though it would be possible to obtain pollen from another botanical garden, we do not want to pollinate our plant – emphasized Dobrzyński.

He explained that there are several reasons, including the fact that the fruiting body developing for over 9 months could significantly weaken our specimen, which would result in the tuber then going dormant for up to a year.

"It's also possible that, under unfavorable conditions, a weakened tuber could die. So we don't want to lose our precious plant," he added.

He noted that there is another way to propagate the arum lily that works very well, but it is a "gardener's secret."

PAP asked how one knows that the plant will flower.

"The development cycle of this plant consists of three stages: vegetative, generative, and dormant. The dormant period can last 2-3 months, or even a year. After this time, the tuber awakens and develops a growing tip, which initially grows very slowly. After about two months, depending on growing conditions, its growth accelerates," said Dobrzyński.

He explained that when an inflorescence grows, it uses the stored reserves from the previous growing season. After flowering for two days, the bulb enters a dormant state again. After this period, the plant produces a leaf to store reserves for the next flowering season.

"The last leaf that emerged from the tuber remained on the plant for 2.5 years. During this time, the plant stored reserves in the tuber. The leaf typically grows to about 5-6 meters tall and looks like a small tree; some may associate it with a small palm tree," the botanist said.

The Warsaw bonsai tuber gains weight every year. Over the past 2.5 years, it has gained an additional 15 kilograms, reaching around 40 kilograms – and that's not a large tuber yet.

"The literature indicates that there are some species of arum whose tubers can weigh over 100 kilograms. The larger the tuber, the larger the inflorescence," noted Piotr Dobrzyński.

Marta Stańczyk (PAP)

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