Tongcao painting, also known as pith paper watercolor, refers to watercolor works created on pith paper. It was one category of export paintings produced in Guangzhou during the Qing Dynasty.

Pith paper is not actually paper, but thin slices cut from the pith of the tongtuo plant. Once processed into sheets, the material is smooth and jade-white, light and delicate in texture. It is especially well suited to watercolor, capable of producing richly vibrant colors, which made it highly favored by painters. However, pith paper is extremely fragile; it wrinkles and tears easily, making it difficult to work with.

In recent years, Hu Jiahong, an inheritor of the intangible cultural heritage of tongcao painting in Jiangxia District, Wuhan, Hubei Province, has created more than 1,000 tongcao paintings. His works span a wide range of subjects, including large composite pieces such as portraits of Zhang Zhidong, Yi Tang He Qi (which directly translates as Harmony in the Household), and the Hankow Customs House, as well as smaller works featuring tigers, apples, portrait studies, and landscapes. Today, in addition to completing his "San Bai Liu Shi Hang" (a common Chinese idiom referring to "all trades and professions") collection, Hu Jiahong has another dream: to open a tongcao painting museum, bringing this niche art form into the broader public view.