Santolina — Lavender Cotton
Santolina from the Mediterranean Basin is commonly called lavender cotton, a confusing name with little if any connection to either of those plants. The Latin derivation translates to “holy flax” in English, but that, too, is obscure. It makes most sense to use the botanical name as the common name, as most gardeners now do.
Santolina thrives in Sonoma County’s rainy winters and hot, dry summers, but it tends to be short-lived and must be replaced after 5 or 6 years. It prefers full sun but grows quite easily in nearly full shade where flowering is diminished. Native to sandy, rocky, infertile soils, it tolerates garden loam or well-amended clay as long as it is well-drained. Once established, santolina requires only infrequent watering; it is completely drought-tolerant, though not as compact, in shaded sites. Over-watering in summer will stimulate fungal growth that can be fatal.
Considered an evergreen sub-shrub for its lower woody stems, Santolina chamaecyparissus forms a rounded, dense, silvery gray mound up to 2 ft. high and wide. It has a compact cultivar ‘Nana’ that grows to only about 1 ft.; ‘Pretty Carol’ and ‘Lemon Queen’ with creamy yellow flowers are each a little taller.
Some gardeners object to the ½ in. yellow button-like summer flowers on tall stems that stand above the blue-gray foliage and remove them. Other gardeners shear plants regularly as a low hedge along walkways or garden borders and never see flowers emerge. Still others combine santolina with a low-growing teucrium (germander) and sculpt them once or twice a year into a classic interwoven knot garden. It can also be used in rock gardens or mixed with other low-water perennials or herbs.
Shearing can present a challenge if plants are ignored for several years and allowed to develop thick, woody lower stems. Regular pruning every one or two years—cutting mounds back severely in late winter or spring just above lower buds—maintains a neat outline and keeps santolina from becoming too leggy, woody, or splitting apart in the middle.
Santolina rosmarinifolia is another species that has a similar growth habit but sports needle-like bright green foliage that is softer but similar to rosemary (Rosmarinus). Flower heads on this species are brighter yellow. The cultivar ‘Morning Mist’ has a compact habit.
Similar to lavender or sage, santolina foliage has a pungent or musty aroma, easily distinguished when leaves are bruised. The strong scent, and possibly taste, deters deer and other browsing animals.
Propagate new plants by taking semi-ripe cuttings in the fall, potting them up in a quality nursery planting mix, and providing bottom heat. You can sow seed in a cold frame in autumn or spring. Plants will occasionally layer themselves, i.e., when a branch bends down and touches moist soil. After roots develop, the branch can be snipped off and replanted elsewhere to start another plant.