white rock rose (Cistus hybridus)
THAT SWEET, musky smell wafting in the air after our recent rain was unmistakable: the intoxicating smell of the rockrose.
Any day now, flowers of the rockrose will open all across the Valley. The plant blooms briefly in the spring and lives for around six years. Its oils, those that impart its musky fragrance, contribute to its combustibility, a desirable trait for a plant whose rejuvenation depends on fire.
Yet, curiously, the rockrose appears on lists of plants that are supposedly fire resistant.
Two local rockrose species are 5- to 7-foot-tall shrubs: orchid rockrose (Cistus x purpureus), with deep orchid-purple blooms; and crimson-spot rockrose (Cistus ladanifer). Three other rockrose species are subshrub or ground-cover types, from 18 inches to 3 feet tall, spreading to a diameter of up to 8 feet: sageleaf rockrose (Cistus salviifolius), with a yellow spot at the base of each white petal; Cistus skanbergii, a distinctive pink-flowered species; and Cistus “Sunset,” with flowers that are deep rose.
Speaking of fragrant Mediterranean plants, I saw a refreshing alternative to a front lawn the other day. It was a yard full of nothing but English lavender.
Rockrose and lavender both crave a fast-draining soil and lots of sun, although they find partial shade tolerable in exceedingly hot and dry climates such as our own. Both are hardy to about 15 degrees Fahrenheit.
Another distinctive March fragrance, similar to orange blossoms, comes from the flowers of the Victorian box. No tree has a more symmetrical, perfectly shaped domed canopy than the Victorian box (Pittosproum undulatum). It is a self-cleaning tree and requires little, if any, pruning and it makes a wonderful screen where its roots are not inhibited by asphalt or concrete.
I should mention two shrubs with fragrant flowers that are heavily planted throughout the Valley, but nearly always struggle, showing either chlorotic or burnt leaves or both: sweet olive (Osmanthus fragrans) and gardenia. Sweet olive has tiny, fruitily fragrant flowers, while gardenia has what many consider to be the most wonderfully perfumed flowers in the world. Both are native to the hot and humid climate of East Asia.
Their habitat explains their tendency to develop chlorosis, a fancy word for yellow leaves lacking iron. Iron is readily available in the acidic soil of East Asia but sorely lacking in the alkaline soil of Southern California. Similarly, our low humidity explains the tendency of sweet olive and gardenia foliage to burn. Both plants require excellent light but need protection from scorching heat.
They benefit from placement next to a block wall, a wooden fence or a large boulder. All of these hardscape features possess water-retaining pores that slowly release water vapor to adjacent plants, elevating the ambient humidity to the plant’s benefit.
TIP OF THE WEEK: Lily-of-the-Valley shrub (Pieris japonica) is a lesser-known but equally desirable plant for the kind of partial or filtered sun, acidic soil microclimate favored by sweet olive and gardenia. Its young leaves are an attractive pinkish bronze and its flowers, which are presently in bloom, are chains of the same delicate urn-shaped blossoms found on manzanita, strawberry tree and other plants in the heather family.
