In the mile-high, sunny and dry west, silver is more valuable in the garden than gold. Gold and variegated foliage effects may be a gardener’s delight in the moist, shady and cloudy east and northwest, but here many of those leaves burn while silver leaves reflect heat and ultraviolet rays. The silver color of plant leaves is caused by fine hairs, microscopic scales or a waxy substance. These structural adaptations improve the drought tolerance of plants by cooling and by reducing water loss through transpiration.
At the same time, I have heard silver plants referred to as “social facilitators”, because silver can help harmonize other colors, softening some colors, intensifying others and contrasting and enlivening foliage greens. Here are descriptions of silver plants for the western garden. Some are common, some are hard to find, some require dry conditions or good drainage, but all will help light up a sunny, western garden while reducing the need for water.
Snow in Summer, Cerastium tomentosa, is common but could be better used. It is very silvery when grown in full sun with little water. The early foliage looks the best, then the flower stems extend and the plant is smothered in 1” white flowers in spring. Then the plant flops and looks sloppy. If it is sheared back immediately to 2”, the clean silvery mat returns. My favorite Cerastium is C. candidissimum. It is a very compact form only half an inch high and 12” wide with very silvery leaves and small white flowers on 2” stems. It also appreciates shearing, and a deep drink after blooming. This is a drought tolerant, elegant gem.
There are several species of Pussytoes. All are low gray-silver mats with short stalks of furry flowers that thrive in dry shade. Antennaria rosea has pinkish flowers. Antennaria parvifolia has cream-white flowers and is the most drought-tolerant. The A. parvifolia variety ‘McClintock’ is mostly flowerless and therefore works better between flagstones. Pussytoes can look good both in naturalistic and formal settings.
Of course the Artemisia sages are famous for their silvery, western look. Big Sage, Artemisia tridentata grows into a 6’-8’ coarse shrub with its famous aromatic foliage that freshens the atmosphere after a rain. Artemisia filifolia, Sand Sage, is a native of theBoulderCountyplains. It has very silvery, thread-like leaves on branched 3’-4’ woody stems. The flowers are not significant, but as the flowering stems elongate, they wave in the breezes, dancing with any nearby grasses. Both these natives make attractive backdrops for red or blue penstemons, Russian Sage or Salvias. A popular landscape Artemisia is A. schmidtiana, known as Silver Mound Artemisia which makes an 18” mound. It is famous for its fine-textured silver foliage and its tendency to fall open and look sad in wet, hot conditions. The ‘Silver King’, ‘Silver Queen’ and ‘Valerie Finnis’ selections of the native Artemisia ludoviciana can be dazzling, but they spread in dry ground like mints spread in moist soil. Artemisia ‘PowisCastle’ makes a shrub-like form 30” high and wide with dissected silvery leaves. It rarely flowers, which is better for the foliage form. Cut it back to a foot tall every fall or spring for best appearance. Just because Artemisias are called sages, don’t try to make your turkey stuffing with them; it will taste like turpentine. Instead, use them to make pungent smudges.
There are three silver tansies that deserve a place in the western garden. Tanacetum niveum, the Snow Daisy, is an 18”-24” tall perennial with fine-textured silver foliage that looks and smells a lot like Feverfew. In late spring, it is covered with masses of 1” white, daisy-like flowers. Once the flowers are faded, quickly dead-head them because they can self-sow very profusely. Deer and rabbits do not eat this plant.
Plant Select has promoted Partridge Feather, Tanacetum densum. It has silvery, feather-like leaves that form a groundcover 6” high and 2’-3’ in diameter. Yellow, button-like flowers rise on short stems above the foliage. It performs well in hot summers and dry soils, and dies out from wet conditions. Occasional spots die out for unknown reasons, but they recover quickly if you rub out the dead area with a gloved hand.
Another attractive Tanacetum, T. albipannosum is a newcomer that grows to 18” x18” with silvery feather-like leaves and big white daisies with yellow centers.
There are several silver Salvias and Plant Select has promoted three of them. Salvia argentea makes a 2’ rosette with huge, woolly silver leaves “…like rhubarb wearing an ermine coat.” The white flowers can be left to form their loose candelabra or removed to keep the foliage looking better. Salvia daghestanica, Platinum Sage, makes a low-growing mat of rosettes that looks good as a xeriscape edging or a compact feature in a dry rock garden. The purple flowers are dramatic against the silver leaves. It likes sun, good drainage and good air circulation. Salvia pachyphylla, Mojave Sage, has silvery green foliage that is very aromatic and semi-evergreen. The form is shrub-like, with woody stems. The flowers are striking with their violet blue against mauve bracts. This Salvia has been difficult for some people to grow. It is very drought- tolerant, and stunning where successful.
Hieracium lanatum has fuzzy, very silvery 4” leaves with wavy margins. It stays a modest plant, 8” high by 10” wide. The dandelion-like flowers are nickel-sized and bloom on tall thin stems. It has proved very hardy and long-lived for us in a south- facing terraced bed for over 12 years.
At our nursery, Harlequin’s Gardens, we discovered a silver leafed form of Teucrium in a group we were growing from seed. We are calling it Teucrium cossonii ‘Silverado’. It forms a dense mat about 4”-8” high and 16”-24” wide of very silvery aromatic foliage. The sweet pineapple fragrance is unattractive to deer, rabbits and grasshoppers. In summer it blooms just above the foliage with pink-lavender flowers. The foliage is just as beautiful in winter as in summer.
Some silvers are almost white. This is the case with Verbascum bombyciferum. The first year, it grows a pretty, innocent rosette that shines with silvery-white down. The second year it sends up 4’-6’ candelabras of silvery-white fur punctuated with soft yellow flowers. These flower stalks sometimes take on fantastic wild shapes. It is a biennial. It’s cousin, Verbascum wiedemannianum, also has white-silver rosettes the first year, but the second year deep purple spikes of flowers shoot up in early spring. This is also a biennial. Verbascums must have two plants to make seeds, and they will make many seedlings which will sport themselves around, where some will have to be weeded and some will put themselves in the most glorious spots.
There are many silver stars, but Lonicera ‘Kintzley’s Ghost’ shines like cascading silver dollars. This remarkable honeysuckle with small yellow flowers was discovered by plant-enthusiast, Scott Skogerboe, in Ft.Collins. It was picked by Plant Select as a winner. The “silver dollars” are round leaves with the stem growing through the center that turn a brilliant silver-white and light up the 10’-15’ vine until frost.
It is probably best to stay away from silver leafed trees. Russian Olive is truly a noxious weed in our water ways. Silver Poplar can send up suckers 30’ away and loves to colonize neighborhoods, and even Sea Buckthorn with its orange, edible berries is thorny and suckering. Our native Silver Buffaloberry, Shepherdia argentea, is more like a big shrub to 10’-14’. It is worth growing, but you need both male and female trees to get the good-tasting red fruit. It does have some thorns, but can make a striking specimen if given a little bonsai pruning.
Because silver-leafed plants are mostly adapted to hot, sunny and drier conditions, they are more difficult to site in non-xeriscapes. Ideally we plant all our low-water plants together and our higher water plants together. If you must plant a silver plant that is fussy about good drainage where it will get irrigated more than once a week, put it on a south-facing slope or where it will get late afternoon sun. Besides being drought tolerant, many silver plants have winter color and are resistant to animal feeding because they are woolly or pungent.
Other silver plants worth searching out are: Inula verbascifolia, Sideritis scardica, Anthemis marschalliana, Hymenoxys argentea, Centaurea bella, Stachys inflata, Stachys byzantina (Lamb’s Ears), Artemisia versicolor ‘Sea Foam’, and Oenothera macrocarpa ‘Silver Blade’.