Amorphophallus ongsakulii

This Arum plant belongs to the so-called geophytes; these are plants that form one or more underground storage organs (in this case, tubers) with which they survive unfavorable conditions (winter, dry season). They are also known as “tuberous aroids”. We also sell most of these plants only as dormant tubers.

Tuberous aroids have a (more or less) strict growth rhythm, and this should be mimicked in cultivation.

Tuberous aroids originate from the undergrowth of (rain)forests, but usually grow in slightly less dense areas. Accordingly, they are adapted to semi-shady locations.

As houseplants, they should be placed where they receive bright but indirect light, e.g., next to a south-facing window or at an east or west-facing window. They tolerate a few hours of sun well, but must be protected from scorching midday sun. The leaf will bend towards the window when grown indoors. Please do NOT rotate the plants regularly. Otherwise, the petiole will become increasingly long and thus unstable.

When cared for under grow lights, e.g., in a plant cabinet, in a terrarium or in a grow tent, moderate lighting is sufficient. At 2,000 to 8,000 Lux or 50 to 180 PPFD (µmol/m²/s), they grow well and their leaves develop ideal coloration.

Species with distinctly dark-colored leaves prefer less light and only develop good coloration under shady conditions.

The tubers are always potted with the eye facing upwards. They can be potted as soon as the central eye of the tuber shows significant growth. This is usually the case from about mid-March.

The pot should be chosen generously. It should be at least three times the diameter of the tuber. For typical round pots, the tuber is planted at about half the pot's height.

Tuberous aroids like loose, airy substrate. They grow perfectly in a mixture of our houseplant mix and coconut chips in a 2:1 ratio. If you want to water a bit more, it's better to use the Aroid Mix or pure coconut chips. With good care, they grow very quickly and should therefore be separated and repotted every year. This should be done in autumn or winter, after the single leaf or leaves have died off. Except for very small species and tropical species from Borneo and Sumatra, the tubers can then be stored dry over winter.

In spring, you can start watering as soon as the leaf begins to push out and unfurl significantly above the substrate. From now on, the plant should always be kept moderately moist and never allowed to dry out completely. It can be watered with medium-hard tap water. Regular flushing with soft water, such as rainwater, distilled water, or RO water, approximately every 3 months, is beneficial and prevents lime accumulation in the substrate.

Tuberous aroids grow quickly, which is why they need a lot of fertilizer. After sprouting during the growing season from approximately April to October, they should be fertilized weekly with a good complete fertilizer (N-P-K + trace elements) for houseplants, such as Wuxal Universal Fertilizer. For smaller species, we recommend adjusting the fertilizer to 500 µS/cm. For larger species, a conductivity of 800 µS/cm is acceptable. The conductivity can be determined with a TDS meter. In the autumn months, fertilization should be reduced, as the plants no longer receive enough light to utilize the nutrients. Watering is also reduced now to induce the dormancy phase. When the leaf begins to turn yellow, watering can be further reduced and eventually stopped completely. After about 2 weeks of dryness and once the leaf has died, the tubers can be removed from the pot. The daughter tubers can be broken off at the point where they attach to the mother tuber.
The tubers should be cleaned, and most species, after drying, should be stored in a cool (approx. 10 to 15 °C), dry place. In spring, they can be moved to a warmer location from March onwards. Fully tropical and dwarf species should be overwintered at 15 to 20 °C in moist sphagnum moss or in substrate. Once the first signs of growth appear, the tubers can be repotted and watered.

If they are only watered with soft water (e.g., when kept in a terrarium), a calcium and magnesium fertilizer (so-called CalMag fertilizer) should also be used.