臺灣原生，一年生草本；莖上部直立，下部伏地，四稜形，被易脫落的長柔毛或細剛毛。葉對生，狹卵形或寬卵圓形，鋸齒緣，兩面被細剛毛或柔毛。總狀花序，頂生，粉紅或粉紫色；花期 7~10月。堅果細小，長圓形，黑色；果期 8~11月。夏秋季收割地上部分，曬乾或曬至半乾，堆疊燜之使發酵變黑，再曬至足乾，即可貯存備用。

Taiwan native, an annual herb; upper stem erect, lower part creeping, 4 ribbed, growing long pubescence or fine bristles easily detached. Leaves opposite, narrowly ovate or broadly ovoid, serrated, with pubescence or bristles on the both sides. Racemes, terminal, pink or pinkish purple; flowering from July to October. Fruits are small nuts, oblong and black; fruiting from August to November. The plant is processed by harvesting all the aerial portions above the root. The portions are then dried or partially dried and piled up in order to allow them to ferment until they are darkened. After the fermentation, they are then thoroughly dried and stored for future use.

生長適溫20~25℃，土壤以富含有機質砂質壤土為佳。以扦插繁殖為主，亦用種子繁殖，忌連作。

The proper growth temperature is 20~25°C, and the soil is preferably sandy loam rich in organic matter. Mainly cutting propagation, followed by seeding. Avoid continuous cropping.

可作庭園地被植物、校園藥用植物。莖葉經發酵曬乾後，加水與少許鹹共同煎汁，再添加少許澱粉漿可製成仙草凍，是夏天常吃的清涼飲品。主治中暑、急性風濕性關節炎、高血壓、感冒、黃疸、急性腎炎、糖尿病、泄瀉、痢疾，燒燙傷、丹毒、梅毒、漆過敏。

It can be ground cover in gardens or medicinal plants in campus. After the stems and leaves are fermented and dried, decoct with water and a small amount of baking soda, and then add a little starch slurry to make jelly which is a refreshing drink often consumed in summer. The extract is reported to treat heat stroke, acute rheumatoid arthritis, hypertension, cold, jaundice, acute nephritis, diabetes, diarrhea, dysentery, burns, erysipelas, syphilis and lacquer allergy.