Sauromatum horsfieldii

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 less dense areas there. Accordingly, they are adapted to semi-shady locations.

As houseplants, they should be placed where they receive bright but rather 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 harsh midday sun. The leaf will bend towards the window in indoor cultivation. Please do NOT rotate the plants regularly. Otherwise, the petiole will grow longer and become unstable.

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

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, which is usually from mid-March onwards.

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

Tuberous aroids prefer 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, use the Aroid Mix or pure coconut chips. With good care, they grow very quickly and should therefore be divided and repotted annually. This should be done in autumn or winter after the single leaf or leaves have died back. 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 water as soon as the leaf begins to push itself clearly above the substrate and unfold. From now on, the plant should always be kept moderately moist and never completely dry out. It can be watered with medium-hard tap water. Regular flushing with soft water, e.g., rainwater, distilled water, or RO water, about 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 setting the fertilizer to 500 µS/cm. For larger species, a conductivity of 800 µS/cm is also suitable. The conductivity can be determined with a TDS meter. In the autumn months, fertilization should be reduced, as the plants then no longer receive enough light to utilize the nutrients. Watering is also reduced now to induce the resting phase. If the leaf starts to turn yellow, watering can be further reduced and eventually stopped completely. After about 2 weeks of dryness and when the leaf has died, the tubers can be removed from the pot. The daughter tubers can be broken off at the point where they connect to the mother tuber.
The tubers should be cleaned, and most species stored after drying in a cool (approx. 10 to 15 °C), dry place. In spring, they can be moved to a warmer location from March. 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 cared for in a terrarium), a calcium and magnesium fertilizer (so-called CalMag fertilizer) should also be used.