Silver sage (salvia argentea) is also known as silver clary or silver clary sage. Silver sage is grown for its striking white leaves. The leaves are wide with scalloped edges and are covered with downy hairs that give them a fuzzy appearance. Do not confuse silver sage with culinary or garden sage (salvia officinalis). Silver sage is not edible.
Silver sage plants are not fussy about soil type (clay, loam, sandy) or soil pH. The do require well-drained soil and at least eight hours of full sun a day. Silver sage is hardy in growing zones 5 through 9, although it can be grown as an annual in colder zones. In mid- to late fall cover your silver sage plants with straw or dried leaves at least two to three weeks before your first predicted frost date. Uncover your plants in mid-spring after all threat of frost has passed. Silver sage can withstand light frost but the outer fuzzy leaves will yellow and die if left exposed to heavy frost or snow.
You will have to start silver sage from seed if you want it in your garden as it is seldom sold as a potted plant. Sow silver sage seeds in mid- to late spring in well-drained soil. Cover with 1/8 inch (just sprinkle a little soil over the top of the seeds) of soil. Seeds will germinate in 21 to 30 days. Gardeners in colder climates can start silver sage indoors four to six weeks before your last frost date. Sprinkle seeds in a seed-starting flat filled with sterile seed starting soil. Cover with 1/8 inch of soil. Place the flat in a bright location. Keep the seeds moist (not wet) until germination. Continue to keep the soil moist until the first rosette of leaves form. Plant silver sage plants outdoors after all threat of frost has passed. Space plants 12 to 18 inches apart.
In its first year, silver sage only produces its fuzzy, white leaves. In its second year of life silver sage will produce flower stalks covered in white, pale pink or yellowish flowers. After the flowers fade and the seed ripens, most silver sage plants die. You can extend the life of your silver sage plant by pruning (cutting off) the flower stalk before the flowers open. Mature plants will form a three foot high by two foot wide clump.
The easiest way to propagate your silver sage plants is to allow it to self-sow. Self-sowing is when a plant flowers, then releases ripened seeds. The parent plant will most likely die after self-sowing, however you will have a ton of baby silver sages germinating the following spring. In the second year of its life most silver sage plants produce off-shoots. These are little (exact) replicas of the parent plant. Gently dig up the off-shoot and re-plant.
Once established, silver sage is quite drought-tolerant. You should not need to give it any additional water unless you live in an area that receives less than three to five inches of water during the growing season. Silver sage will thrive on 1/2 to one inch of water a week. Over-watering silver sage is a common mistake. Over-watered plants will succumb to root rot and bacterial or fungal diseases.
Mix two to three cups of compost or balanced (10-10-10 or 12-12-12) commercial or organic fertilizer into the soil before sowing or planting silver sage seeds or plants. Apply a balanced organic or commercial fertilizer to your two-year-old and older silver sage plants (according to package directions) in mid- to late spring.
Remove yellowed, browning or diseased leaves as soon as you notice them. Prune off flower stems by cutting them as close to the base of the plant as possible. Do this before flowers open or just after flowers open. If you wait until the flowers begin to fade and set seed, your silver sage plant might die as it thinks its life cycle is over.