What is Saxifraga?

Saxifraga is a plant genus that is part of the Saxifragaceae family. It contains over 450 species of perennial and annual plants that are usually found in the north and south temperate zones, often with the common name "rockfoil." The foliage is characterized by a circular shape in which the leaves emerge from a common point, and the flowers are generally red to creamy white. Most saxifraga plants live in or around rocks. In fact, the name "saxifraga" is derived from the Latin words saxum and frangor, which translate to "a rock" and "to break" respectively.

There are several categories within the saxifraga genus including the Kabschia, the Engleria and the Porphyrion, all of which generally bloom in January and February. Other varieties, including Dactyloides, Euaizoonia, and Trachyphyllum, have a longer blooming period that typically extends well into spring and early summer. Most of these plants are grown in rock gardens but a few species, such as S. sarmentosa, can be grown as a houseplant.

Typically, a well-draining moist soil that is slightly alkaline is required for optimal saxifraga growth. Mossy plants, such as the Dactyloides, do well if a mixture of loam and sand is sprinkled on top of the soil as the plant grows. Kabschia plants typically require lots of crushed rocks, usually limestone, in the soil for adequate drainage. They also take advantage of an occasional topping of the soil with a mixture of sifted loam, leaf mold and sand.

Saxifraga plants shouldn't be grown in full sunlight, as the leaves tend to fade after prolonged exposure to the sun. An area that is partially shaded during the day and has good ventilation is a good setting for the plant. They generally do not tolerate high humidity and over watering can cause the color of the leaves to change to yellow.

Certain insects live and feed on the saxifraga including aphids and cochineals. A large infestation of aphids is particularly worrisome as they tend to cause curling and yellowing of leaves and stunting of shoots. Another concern with aphids is the secretions that are left on the stems and leaves. The sticky residue, called honeydew, generally attracts the fungal spores of the sooty mold, which blackens the plant. These problems are generally treated with a spray of insecticidal soap.

Saxifraga plants are propagated by seeds, cutting and division. Seedlings take several years bloom, while divisions of mature plants typically need just one season to start blooming. Single leaf rosettes are usually cut between the spring and fall and are typically placed in a pan of sand. Within a few weeks, roots begin to emerge and the cutting is transplanted into a pot with well-draining soil.