Downoi

Description

Pogostemon helferi, also known as "daonoi" or "downoi", is an aquarium plant that has been known to science for over 120 years but was only discovered for aquaristic purposes in 1996 by Nonn Panitvong and Arthit Prasartkul. It originates from a fast-flowing river with limestone ground in the Thai province of Kanchanaburi, near Myanmar. The plant grows on and between rocks, submerged during most of the rainy season, and often in strong currents. During autumn and winter, it forms upright shoots with striking flower spikes typical for the genus Pogostemon. Pogostemon helferi is easy to cultivate if specific requirements are met: sufficient light (0.5-1+ watt per liter), ample CO2 supply, and adequate levels of fertiliser including nitrate, phosphate, potassium, and magnesium. It requires a lot of iron, which it responds to with lush green leaf color. Insufficient light induces etiolation, causing internodes to lengthen and leaf color to change to yellowish. Propagation is easy using a cutting tool with sharp edges, cutting shortly under a node. Shortening lower leaves can improve holding in the substrate. Planting is best done with plant tweezers to avoid bruising. This species is best suited for accentuating the middleground in nano or small aquariums and can be placed in the foreground of larger tanks. When handling Pogostemon helferi, be careful not to bruise it, as this may lead to dieback. The plant can be attached to wood or rocks using a nylon thread, ensuring not to draw it too tight. It is also suitable for paludariums and can be cultivated partially emersed, partially submerged.