Rosemary or green santolina and gray santolina are evergreen subshrubs that typically grow from 12 to 18 inches tall and spread out 3 to 5 feet to form a mounding groundcover. Divided, linear leaves are about 2 inches long but only 1/16 of an inch wide. Leaves with finely toothed edges are tightly massed on the stem giving plants a feathery appearance. Half-inch, yellow, button-like flowers bloom in spring and stretch their stems to about two feet tall. The leaves of rosemary santolina are bright green while those of gray santolina or lavender cotton are silvery gray.
Santolina neapolitana differs significantly from the other two species of santolina. While the leaves are still recognizable as members of the genus, the plant is more shrublike and grows taller than its cousins. Topping out at two to three feet tall and wide, clusters of soft yellow flowers reach above the foliage in spring.
PlantFiles on Dave's Garden refer to S. neapolitana as Santolina pinnata subsp. neapolitana. APG III has given this plant its own species name, and since I use this taxonomic system as my authority, I will follow their lead and call it S. neapolitana. Interesting cultivars include 'Edward Bowles' and ‘Lemon Queen'. A picture of the plant is posted on PlantFiles by bonitin.
Plant santolina in light, sandy, well drained soil in full sun. Once established, very little supplemental water is needed, and plants may even rot if kept too damp. Save your soil amendments for other plants, for santolina does not need rich soil. It does quite well left to its own devices with little or no fertilizer. Temperatures down to 0°F are tolerated, so it is hardy in large portions of the country.
Santolina prefers dry calcareous or alkaline soil, and tolerates poor, gravely soil. However, I grow it in my Zone 8B garden where the sandy soil is slightly acidic. Performance is enhanced by the addition of a bit of lime to the soil. I have grown santolina for years, but it never looks quite as good as plants I have seen in other places. While I enjoy growing santolina for its fragrance and for its use in crafts, I suspect that it does better in parts of the country where the humidity is not as high and the soil is a bit more alkaline.
After a few years, santolina tends to split open in the center. Discourage this condition by pruning in early spring before new growth begins. Plants that are pruned drastically in spring most likely will not bloom, but such shearing will rejuvenate the plant. Remove flower stalks when bloom is finished and they have become unsightly.
Despite efforts to keep the same plants in the garden over long periods of time, they eventually reach the point where they are so leggy and open-centered that they are no longer attractive. Then is the time to replace them with fresh young plants for several more years of enjoyment.
Use seeds or cuttings to start new plants. Sow seeds in flats or pots in early spring or take three- to four-inch cuttings in midsummer and place in a moist but freely-draining potting medium. Within two weeks roots should form. Let them grow in the containers for a couple of months before transplanting to the garden. Layering is easy since the plant is very low to the ground. Simply scar the bottom of a branch and cover it with soil. These layered branches can be separated from the parent plant and planted in the landscape after a few months.
Santolina is a great addition to herbal crafts. A dozen or so stems of gray santolina cut and bound with a piece of twine or a rubber band and hung upside down in a dry, airy place retain their silvery color and benzoin-like fragrance. In a few weeks they are dry enough to work into a wreath with other dried herbs. The button-like flowers dry well, too, and provide additional decoration for wreaths and other crafts.
Children visiting my garden enjoy using santolina as a component in potpourri. They place stems of santolina along with other fragrant foliage, flowers, cones, sticks, and various plant parts in a sachet bag or small pillow to take home.
Besides its decorative uses, a decoction can be made from the flowers and leaves that is said to expel intestinal parasites. The perfume industry extracts oils from the plants for use in making perfumes. Some people put a few of the stems in chests of drawers and closets where they effectively repel moths. Dried crumbled leaves are said to make a pleasant flavoring for some dishes, though I have never used them as such. Leaves rubbed on insect bites reputedly relieve the pain of the sting, and the yellow flowers can be boiled to make a bright yellow dye.
The santolinas are plants with many uses, but chief among them is simply their use as attractive, undemanding landscape plants that are easy to care for and have few pests. That alone is sufficient reason to include them in your garden.