About Saxifraga L.
Saxifraga paniculata is a perennial, stoloniferous herbaceous plant, with flowering stems growing 10 to 30 centimeters tall. Its most easily identifiable feature is a very dense basal rosette of leaves. These leaves are leathery, flat, stiff, 1–3 cm long, oblong to ovate, and covered in dense teeth along their fine margins. A lime-encrusted white pore is located at the base of each leaf. Rosettes grow at the tips of long horizontal stolons (runners), and rosettes may sometimes not produce any flowering stems for a few years. When flowering stems do grow, they are erect, bear reduced scattered leaves, and end in a somewhat elongated cluster of flowers. The flowers are white, around 1 cm across, and marked with purplish or red dots. Flowering occurs from mid-to-late June to early August. All flowers of this species are perfect, meaning they contain both stamens and carpels; each flower has five petals, two styles, one inferior ovary, and a two-beaked seed capsule. In 1909, Warming observed that the flowers are protandrous: they produce and disperse pollen before their stigmas become receptive. Even so, this plant is capable of self-pollination. Saxifraga paniculata can sometimes be confused with Saxifraga tricuspidata (prickly saxifrage), a species in the same genus that grows in a similar range. The two can be told apart because S. tricuspidata lacks lime-encrusted leaf-base pores, and it has crowded, much narrower leaves with mostly smooth margins, ending in three stiff, spine-tipped teeth. Saxifraga paniculata grows across the Circumboreal Region. It can be found throughout Central Europe, Greenland, Iceland, Scandinavia, the Caucasus, and North America. In North America, it occurs in the northern Great Lakes region, New England, and New York State. Only historical records confirm its former presence in Maine. It is currently present but rare in Vermont, Nova Scotia, Newfoundland Island, New Brunswick, Minnesota, and Labrador. This species is a calciphile, meaning it requires calcareous growing conditions, and is typically found in crevices of basic rocks, including basalt and volcanic rock conglomerates. It prefers shady rock crevices and rock ledges. Saxifraga paniculata is able to close its leaf rosettes during harmful environmental conditions such as extreme heat and drought. This ability gives it very high resistance to sustained photoinhibition and irreversible dehydration. A 2006 paper by Hacker and Neuner found that S. paniculata is more resistant to cold-induced winter photoinhibition than any other evergreen subalpine species the research group studied. Because of the short growing season in its native range and potential lack of pollinators, S. paniculata (like many arctic plants) can self-pollinate. While self-pollination is usually avoided by plant species as it does not produce offspring with genetic variation, it allows this species to produce and disperse seeds even under poor conditions. In the wild, S. paniculata has been observed growing alongside a wide range of associated species, including Trisetum spicatum, Polygonum viviparum, Polypodium virginianum, Sagina nodosa, Woodsia alpina, Campanula rotundifolia, Rubus pubescens, Aralia nudicaulis, Tortella tortuosa, Aquilegia canadensis, Carex eburnea, Woodsia glabella, and lichens. Saxifraga paniculata is cultivated as an ornamental garden plant. It is hardy, but it cannot tolerate winter wetness, and requires very sharp drainage in alkaline or neutral soil. For this reason, it is most often grown in rock gardens or alpine houses. It has produced many hybrids and cultivated varieties. Three of its cultivars have received the Royal Horticultural Society's Award of Garden Merit: 'Lavagreana', 'Rosea', and 'Venetia'.
