by Robert Paul Hudson
Pogostemon helferi was discovered in Thailand where it was given the name “dao noi” which means “little star”. Some how the Thai name has been represented by the word downoi to look like an English word instead of translating the meaning of the word.
P. helferi is a plant that goes thru a drastic transformation, no less remarkable than a caterpillar morphing to a butterfly. In shallow, muddy wetlands, it grows long stems with tiny almond shaped leaves. When submersed underwater, each small leaf turns into a four or five point star. Roots form at the base. Under intense light in the aquarium, each star grows larger but retains its shape. Under lower light levels a stem forms in the center of the star and grows toward the water surface and above, reverting back to its prior form.
It also appears to grow in fast moving rivers according to a video shot by Tropica. In this video the plant is growing attached to rock both above water and below water keeping its underwater form in both cases.
Both growth forms have recently become commercially available. The emergent growth form is usually potted. Either lay the stems horizontal across the substrate or plant the stems upright. It will take about thirty days or less depending on the light intensity for the metamorphosis to begin. Once the stars have formed, cut each off the stems and plant in rows or groups in the substrate. Make sure they are positioned in an open area that is not over shadowed by other plants.
The submersed growth form may be purchased either potted or bare root, and is usually branched with multiple stars, or growing partially upright and branched. Each star may be removed and planted. Sometimes you may find only one or two stars in a pot that are somewhat grown out.
It appears to do just as well in hard water as soft water, and a pH of 6.0 to 7.5. Other than light, the only other important issue is having a fertile substrate. I would add a fertilizer tablet in the gravel under each plant when first planting. Supplemental C02 will help to speed up growth, but only if the light is adequate.