When it blooms, the news goes around the world. A webcam is aimed at them so that every interested gardener can experience the unique process live. The Titan Arum is rightly called the largest flower in the world, because its dimensions are really impressive. Its single flower grows to 2 meters and taller and is surrounded by a single, deep red bract. Only when the underground tuber exceeds a weight of 20 kg is there any chance that the Amorphophallus titanum will ever flower. The record so far is a whopping 117 kg. Even in its native Sumatra it is very rare. In the rest of the world, the titan arum is so unique that a detailed record is kept of every flower and the botanical garden in which it is currently blooming is even open at night.
Table of Contents
Knowledge of botanical systematics
The flowering plant develops from a tuber as an outlasting organ. The most successful cultivations came with tubers that came from Sumatra. The University of Kiel reports that 15 years after germination a vigorous tuber had developed. During this time, it formed a single leaf that supplied the tuber with nutrients and allowed it to grow year after year. On average, this foliage leaf lasts between 12 and 20 months before it retires and a vegetative hiatus of several months occurs. In this phase, the titan arum ‘starts’ to sprout the inflorescence.
The actual male and female flowers are tiny and are located at the base of the sprouting plant. The fascination of the Titan Arum comes from the gigantic bract, the spartha, which encloses the flowers and is deep red on the inside. The petiole, the spadix, in the middle stretches 3 meters and more towards the sky.
Then the Amorphophallus titanum begins to stink of carrion and decay. This tactic is intended to attract insects that crawl into the plant via the leaf blade and lay their eggs there. They also carry the pollen with them and in this way ensure the pollination of the titan arum, provided they have visited another amorphophallus beforehand. They are not rewarded for this activity, because the plant has only pretended that there is food for the larvae there. Therefore, it is also called the deceptive flower. However, the flower has achieved its goal and over the next 8 months develops an infructescence with countless, bright red berries that can reach a height of 2 meters. As a result, the Titan Arum will inevitably die.
If there is no pollination, the flower withers within 3 days; Of course, a new vegetation phase begins that lasts for many years. For this reason, flowering can only be expected every 10 to 15 years. Caring for such a demanding and delicate plant is undoubtedly the ultimate challenge for any gardener.
Only hobby gardeners who have a very warm greenhouse with high humidity can even consider cultivating a titan arum. The following site conditions are required:
- Temperature of at least 24° and at most 34° Celsius.
- Best chance of success at an average of 26° Celsius.
- Relative humidity of 80% to 85%.
- Light-flooded location from April to October.
- Shading against midday sun.
- Substrate made of 3 parts standard soil and 1 part sand.
- Keep slightly moist at all times.
- Avoid waterlogging.
- If the leaf withers, watering is reduced to a minimum.
- Don’t let the flower dry out.
The titan arum keeps changing from a vegetation period that lasts 12 to 20 months to a rest period that lasts 2 to 4 months, in some cases extending to 18 months. The giant flower must therefore be kept in constant view of whether a new leaf is emerging from the tuber or whether the existing one is beginning to wither, because the dose of water depends on this.
Such a huge flower needs sufficient nutrients so that it can form the large bulb and thus the long-awaited inflorescence. Proper fertilization is therefore essential for successful care of the Titan Arum. Experienced experts who have already been able to flower an Amorphophallus titanum recommend the following procedure:
- From March to October, Wuxal super 8/8/6 once a week.
- Dilute fertilizer with water to 3%.
- Administer in the morning or evening only.
- Water until the water-fertilizer mixture overflows.
- Fertilize every 3 weeks from November to February.
- If the leaves turn yellow, stop fertilizing.
- Repot annually during dormancy.
Wuxal super is a high-quality liquid fertilizer that consists of 8% nitrogen, 8% phosphate and 6% potassium oxide as well as other ingredients.
Propagating the Titan Arum in culture is extremely problematic. In the wild, the flower has developed an effective tactic. Since it only has a maximum of 3 days to attract the insects with the pollen, the tall petiole emits a repulsive stench for humans, which smells like carrion and rotting fish. During this period, the temperature inside the flower rises by 10° Celsius compared to the ambient temperature, in order to enhance this smell. The Titan Arum prevents self-pollination by only opening the female flowers in the first night. These have already withered by the second night when the male flowers open. Pollination is therefore done by hand in the botanical gardens. The hobby gardener therefore only has the choice between the following two methods:
If you have the opportunity to get hold of one or more of the fruits, you shouldn’t hesitate for long, but take the seeds out of the still fresh pulp by hand. Since sterile work during sowing is of the utmost importance, gardeners either wear appropriate gloves or thoroughly disinfect their hands beforehand and in between.
Each seed comes in an ideally clear 9cm pot filled with the above mixture. Each grow pot has a drainage hole covered with fine gravel or perlite drainage. To ensure the sterility of the substrate, put it in the oven for 20 minutes at 200° or in the microwave for 10 minutes at 800 watts. The seed is planted vertically or horizontally 5 mm deep in the soil, which is constantly kept slightly moist but not dripping wet. With an average air and soil temperature of 26° Celsius, patience is now required until germination begins.
Since titan arums cannot be pressed into any time frame and even experienced scientists are often completely wrong with their predictions, the garden lover simply waits and sees. After about 2 to 6 weeks, the first tentative budding should appear. However, if the seeds were sown in autumn or winter, it may take up to 6 months to germinate because the seed immediately goes dormant.
This form of propagating a titan arum is also a viable option for less experienced hobby gardeners. Since Amorphophallus titan does not form rhizomes or runners, propagation by leaf cuttings is the only alternative to seed propagation. The following material is required:
- Transparent plastic container with a lid.
- Several 9cm clear pots with drainage hole.
- Sharp knife.
- alcohol for disinfection.
- Rooting powder for leaf cuttings.
- Fine-grained, inorganic substrate.
The transparency of the growing pots makes it easier to control root formation. An extract from seaweed, which is available in specialist shops and online shops, has proven itself as a rooting powder. If the material is ready, the experienced gardener proceeds as follows:
- Pick a healthy leaf.
- Cut off with the disinfected knife in the early morning.
- Cut occurs just above a branch.
- Do not crush tissue with the knife.
- The ideal length of the cutting is 10 cm to 20 cm.
- Remove a maximum of one third of the leaf of the mother plant.
- Dip the cuttings in the rooting powder.
- Stick in the pot with the inorganic substrate.
- Place the pot in the plastic container and close the lid.
- The tip of the leaf must not touch the lid.
- Place the container in a semi-shady spot at 25° Celsius.
- Air the lid from time to time and mist the cuttings with water.
Leaves that are 1 to 3 months old have the best conditions to be used as leaf cuttings. If they are older, there is a risk that they are already preparing to retreat into the tuber. Pumice and perlite are best suited as substrates. Containers and cuttings are inspected daily for water requirements and root development. After about 3 months, the first tender roots should appear and the formation of the small tuber should begin. If the first leaves turn yellow, this is no reason to panic, as this is an indication that the young tuber is entering its first dormant period.
diseases and pests
In principle, sterility is the top priority for all work involving the Titan Arum, as the flower is extremely susceptible to nematode rot, especially during the dormant phase. The rot is usually caused by soil that is too moist and temperatures that are too low, which make it easy for fungi, nematodes and bacteria to attack the tuber. If the damage is recognized in time, a rescue attempt can be started:
- Cut out rotten areas down to the healthy tissue.
- Dust the remaining tuber generously with charcoal powder.
- Store in a dry place in the air for a few days.
- Then replant in moderately moist soil.
- Cultivate drier than before, but don’t let it dry out.
If nematodes were the cause of the rot, the titan arum must be kept in quarantine immediately so that the infection cannot spread. Effective nematocides for private use have not yet been approved, so gardeners can only hope that the rescue attempt was successful.
Among the pests, it is primarily the root aphids that can attack a titan arum. If the tuber is kept a little drier during the dormant period than when it is growing, the pests feel particularly comfortable. Therefore, every repot should be used to thoroughly inspect the tuber for root aphids. Experienced experts advise against the use of chemical pesticides because Titan Arum can react very sensitively to them. It makes more sense to use predatory mites, the natural predators of root aphids. Predatory mites can be purchased in specialist shops. They are applied above and below ground on the Titan Arum and immediately attack the pests without causing any damage to the plant.
Ever since the titanic arum was discovered in Sumatra in 1878, it has stirred the minds of gardeners all over the world. Its spectacular appearance, rare flowering and unusual tactics of pollination by spreading an unbearable stench make the world’s largest flower a real celebrity. Cultivating them presents the hobby gardener with unexpected challenges. However, those who manage to animate the Amorphophallus titanum to flower will secure a place in the botanical history books.