Winter Wonderland of Silvery Foliage

wormwood (Artemisia versicolor 'Sea Foam')

wormwood (Artemisia versicolor ‘Sea Foam’)

Although frost is encountered in the Valley on no more than a few nights each winter, and the possibility of snow falling here is virtually nil, there are plants which, either through silver foliage or dazzling white flowers, provide a wintry touch to Valley gardens.
Where silver foliage is concerned, the discussion invariably turns to dusty millers, named for those who used to mill wheat and were typically covered with a dusty coating of silvery flour. All dusty millers belong to the daisy family, are perennials that may live up to half a dozen years, and are water thrifty. Their leaves are covered with soft insulating hairs and their silvery sheen reflects light characteristics that allow them to head the list of sun-loving plants.
Dusty millers are found in three genera: Senecio, Artemisia and Centaurea. Senecio dusty millers are most commonly seen. These are typically used in flower beds that contain scarlet salvia (Salvia splendens), marine blue lobelia (Lobelia erinus), solid yellow pansies or any other annuals or perennials with vivid primary color blooms. The foliage of the low-growing Senecios provides a sharp and arresting contrast to these flowers. Senecios may also be used as a border around Martha Washington geraniums, whose strong pastel colors are on display in late winter and early spring.
Among dusty millers, Artemisias have the laciest leaves. Artemisia absinthium grows into a 3-to-4-foot shrub while Artemisia ‘Powis Castle’ is a mounding dwarf.  Artemisia versicolor  ‘Sea Foam’ is a burgeoning delight that comes at you in foamy waves.   Artemisias are famous for the alcoholic beverages made from them: absinthe, Pernod and vermouth. Vermouth is etymologically derived from the German equivalent for wormwood, a name given on account of its ability to dispel worms that were once thought to be responsible for upset stomachs.
Artemisia californica is a native dusty miller that may be found growing wild wherever you find undeveloped sloping terrain on the outskirts of metropolitan Los Angeles.
Last but not least, velvet centaurea (Centaurea gymnocarpa) is a plant for every drought-tolerant garden since it grows with a bare minimum of water, whether exposed to full sun or shaded by tall trees. It grows to a height of 3 feet and bears rose-violet flowers. It is easily cloned from 4-to-6-inch shoot tip cuttings. Insert them directly into fast draining soil, in pots or in the garden, from late fall to early spring.
When it comes to brilliant, glistening, snowy white flowers, no plant surpasses sweet alyssum (Lobularia maritime). Although it is the simplest of ornamental plants, since all it does is show off a glimmering if not blinding whiteness, it may be utilized in any planting scheme with memorable effect.
We sometimes forget that beauty and simplicity are allies, not adversaries. And though familiarity is supposed to breed contempt, there is also a refined appreciation for plants that comes with time, allowing us to discover new virtues in species that we may have been acquainted with for years.
Sweet alyssum is available nearly year-round in six-packs and 4-inch quart containers, but it also sprouts from seed – packets are available at every nursery – as easily as grass. It thrives in full to partial sun and has a pleasant fragrance.
Sweet alyssum, also known as sweet Alice, is native to southern Europe, where it grows on cliffs dangling over the sea. Salt and wind do not upset its equilibrium.
Alyssum is famously planted in repeating patterns, where it alternates with mounding dark or light blue lobelia (Lobelia erinus) or both. I have also seen individual white alyssum plants growing as discrete mounds in eclectically mixed planter beds. As stand-alone subjects, they are pleasing to the eye but they also combine well with everything from liatris to lavender.
Sweet alyssum grows well in winter with significant cold tolerance. It belongs to the hardy Brassicaceae or mustard family. The old name for this family – plant names never stop changing – was Cruciferae, which was and forever would have been an entirely proper and logical name because the flower petals of each cruciferous plant are in the shape of a cross. Perhaps the name was changed in honor of Brassica oleracea, the most protean of plant species.
Among the various subspecies and cultivars of Brassica oleracea are the following: cabbage, broccoli, cauliflower, brussels sprout, kale, kohlrabi and collard green. Not to forget broccoflower, a hybrid of broccoli and cauliflower, which you may have seen in the market (looking like a pale green cauliflower), and ornamental kale – that ruffled white or purple lettucelike ornamental that is used in winter as a bedding plant.
A notable group of alyssum relatives with special merit are the wallflowers (Erysimum spp.), which are solid globes of color in late winter and early spring. Wallflowers are grown as annuals, biennials and perennials, with flowers in yellow, orange, red, mauve or brown. Like alyssum, they grow in full or partial sun. Wallflowers get their name from an imprisoned 14th century maiden who fell to her death while trying to escape over a wall to meet her lover.
Stock (Matthiola incana) is another annual white winter bloomer although, similar to alyssum, it has purple and deep rose cultivars as well. Stock, by the way, got its name from the fact that its flowers are wrapped stiffly around the stem much like a certain kind of clergyman’s collar also known as a stock. According to flower expert Stirling Macoboy, “stock are rarely grown to good quality in the home garden” because they need the kind of heavily composted soil that few people are able or willing to provide. It is advised to wait several years before planting stock in the same winter garden spot because of soil pathogens specific to them that proliferate in their presence. Stock flowers are spicily fragrant and are meant to be cut for vase arrangements.
Tip of the Week
Want to take a step beyond the ordinary in selecting an indoor or patio container plant? Consider a long leaf weeping ficus (Ficus ‘Alii’), above. This attractive tree has cultural requirements similar to the more common weeping fig (Ficus benjamina), except that it is slower growing and thus easier to keep confined to its container. With any container plant, once its roots fill the pot, extract it and symmetrically pare down its root ball by one-third. Refill the container with fresh soil and replant. By regular paring of the root ball, you can keep a plant in the same container for many, many yea

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