Although Yangmingshan National Park is located in the subtropical zone, its vegetation differs from that of other areas at similar latitudes for the following two reasons. Firstly, post-volcanic activity means that the soil in the park is unusually warm, lacking in calcium, and strongly acidic. Secondly, the winter northeasterly monsoon brings superabundant rainfall and markedly lowers temperatures, which means that in addition to subtropical rain forest, temperate evergreen broad-leaved forest and mountain- ridge short grassy plains, the park even contains alpine plants that grow in the Central Range at a height of 2500 meters above sea level.
There are currently some 1,359 species of plants in the park, growing in water plant and land plant propagation environments. The land plant environments can roughly be divided into grassy plains, arrow bamboo forest, broad-leaved forest, and afforestation zones.
Silvergrass (Miscanthus floridules), a hardy member of the Gramineae family, often grows on terrain that is too forbidding for other plants, and is one of the most common types of grassy plant in Taiwan. The silvergrass in Yangmingshan National Park varies in appearance according to the different places in which it grows. The area around Xiaoyukeng, Macao, Lengshuikeng, Dayoukeng and Qingtiangang, for example, is covered by a thin layer of loose soil that has been eroded by geothermal warmth and high acidity. Only a small minority of plants such as lichen, mosses, liverworts and blue-green algae, which can tolerate strong acidity, can survive there. On slopes which are swathed in warm volcanic mist, however, only silvergrass can grow, forming extensive silvergrass grasslands. Here the silvergrass is much shorter stemmed than elsewhere, and the tassel is red rather than white. Each year in September and October, parts of Yangmingshan are carpeted in redtasseled silvergrass in full bloom.
Arrow bamboo only grows to a height of one or two meters. Its slender resilient stem was often used by Taiwan's aborigines to make arrow shafts, hence the name. The type of arrow bamboo that grows at Yangmingshan, Usawa cane, is one of three types of arrow bamboo found in Taiwan. In Yangmingshan National Park, it only occurs on sheltered, sunny slopes at elevations of over 800 meters, such as the ridges of Mt. Zhuzi, Mt.Xiaoguanyin, Mt. Datun, and Mt. Qixing. It is one of the park's principal dominant plants.
In Yangmingshan National Park, broad-leaved forest is found in areas between 500 and 900 meters above sea level. The main trees tend to be taller members of the Lauraceae family, such as the common red nanmu and the large-leaved nanmu, accompanied by trees such as the wheel stamen tree, Formosan sweet gum, Taiwan cherry, Japanese cleyera, and dark spotted cherry, together with shorter bushes such as the eurya, purple wood nettle, and narrow- petaled hydrangea. Along with grassy plants and vines that interpenetrate the forest, all this forms a plant world with considerable vertical variation. Broad-leaved forest also provides birds, insects, mammals and amphibians of many kinds with an excellent habitat to nest, and forage for food.
Yangmingshan's artificial forests were all planted in afforestation programs during the Japanese occupation period. These mainly consist of Luchu pine, Peacock pine, black pine and Taiwan acacia, and are distributed in the Mt. Datun and Mt. Qixing areas.
Yangmingshan's water plants are mostly found in marshes and lakes in volcanic craters, such as Menghuan Pond, Xiangtian Pond, Huangzui Pond and Mt. Dajianhou Marsh. Best known among these is Menghuan Pond on Mt. Qixing (elevation 850 meters), whose floor is lined with a thick layer of humus soil. Among its many types of water plants, the pond is particularly noted for one rare type of submerged water fern - the Taiwan isoetes. Other companion plants found on Mt. Qixing include the pipewort, Eleocharis japonica, Schoenoplectus mucronatus, Juncus effusus and Eleocharis dulcis.
Water levels in these ponds vary considerably according to seasonal rainfall, so the water plants found there are difficult to classify simply into submerged, emerged or hydrosere plants, tending to combine features of two or three ecological niches.