There’s a scourge destroying trees in the San Francisco Bay Area. It’s a tiny insect, a thrips, called Klambothrips myopori, and it destroys only one kind of tree: Myoporum laetum. The Maori name for this New Zealand native plant is ngaio, and it’s a self-effacing workhorse found in landscapes all around the Bay.
Fast-growing and tolerant of drought and intense coastal expPostsosure, myoporum has been a useful street tree, a good big hedge, and a billowy large shrub in no-water and low-water landscapes. Its bright, almost succulent evergreen leaves and fragrant white flowers flecked with lavender contribute a lushness to the often gray or olive tones of no-water landscapes. In Southern California, myoporum has become an invasive pest in waterways, especially near the coast, but in the Bay Area it’s not especially aggressive, though here’s an example of one growing at Calera Creek in Pacifica.
Wholesale growers in Santa Barbara have introduced a new variety of this species called Myoporum ‘Green N Clean’ that resists the thrips. However, because of the species’s invasive tendencies and the newness and thus limited availability of this thrips-resistant cultivar, now’s a good time to consider trees that can serve similar functions in the landscape.
In the Australian genus Melaleuca, tea trees, the many species can range from sprawling shrubs to upright trees; several can work well as fast-growing hedges and dome-shaped trees that tolerate moderate sea winds in the Bay Area. Many tolerate wet soils while offering good tolerance to drought as well. Many of them produce pleasing and even showy flowers. The snow-in-summer tree, Melaleuca linariifolia, makes a dome-like canopy with its tiny green leaves and its thick trunk covered in spongy, pale, peeling bark. In June pale-cream flowers cover its crown so thickly as to earn its common name. It’s not nearly so fast a grower as myoporum, but it’s also less prone to breakage and not known to be invasive in California. Other melaleucas that can take the place of Myoporum laetum include Melaleuca styphelioides, prickly paperbark, a slightly weeping variety with bristly leaves that can get much taller (70ft) but otherwise similar to M. linariifolia; and Melaleuca armillaris. The latter makes a luscious, sprawling informal hedge or can be trained into a wonderful tree. Unlike the previous two “paperbarks,” its bark resembles that of a linden or an American elm, with lovely sinuous striations developing over time, and its cream-colored flowers resemble bottlebrushes in form.
Another Australian tree that can serve in some of myoporum’s roles is the water gum, Tristaniopsis laurina, especially the broad-leafed variety called ‘Elegant’. Its resemblance comes in the form of deep, shiny green foliage and fairly good tolerance of coastal winds. Its rounded profile in youth also adds to the similarity, though its ultimate size surpasses that of myoporum. Also pleasing, and unlike myoporum, are its fragrant golden flowers and jigsaw-puzzle-like peeling bark.
For tolerance of salty and foggy winds, few plants can match Myoporum laetum. The drought-tolerant New Zealand Christmas tree, Metrosideros excelsa, bears up well in very foggy and windy districts of San Francisco but has not been used so extensively as myoporum on the front lines of coastal exposure in the Bay Area. In its home country it’s frequently photographed hanging out over salt water, and its Maori name, pohutukawa, means “sprinkled by spray.” These adaptations as well as its pleasing gray-green foliage and red bloom in spring and early summer should earn it more frequent planting in the harshest seaside places where myoporum has until now ruled. The downsides to this tree are its eventual size, ranging as tall as 70 feet and at least as wide, and, for some people, the aerial roots that hang down from its branches and sometimes develop into secondary trunks.
Natives such as Garrya elliptica (tassel bush), Rhus integrifolia (lemonade berry), Rhus ovata (sugar bush), and Malosma laurina (laurel sumac) can serve some of the shrub functions of myoporum in coastal areas. In slightly more protected spots, coast live oak (Quercus agrifolia), California bay (Umbellularia californica), and toyon (Heteromeles arbutifolia) can reach tree-like proportions where salty winds have influence. For a showy, exotic alternative, consider planting Banksia praemorsa, the cut-leaf banksia. In its habitat on the south coast of Western Australia it is subjected to powerful winds off the Southern Ocean. Few plants that can stand up to chilly, salty sea winds, impoverished soils, and a long, dry summer produce such a remarkably beautiful flower cluster on such pleasing foliage.