UNITED STATES—The climate here is pretty cool, at least in winter. Right now, it is pleasantly warm. It does not often get uncomfortably cold or hot, and when it does, it does not stay like that for too long. In between the warmest days of summer, the nights typically cool off nicely. In between the coolest nights of winter, the days typically warm up nicely. Humidity is normally minimal. Rain is adequate in season.
We have here what is known as a ‘Mediterranean’ climate. Obviously, it is similar to many climates of the Mediterranean Basin. Beyond the Mediterranean region, there are not many other places in the world that enjoy such reliably temperate weather. Most of such places are in southern and southwestern Australia, the Western Cape of South Africa, central Chile, and evidently, right here.
This particular region of Mediterranean climate is quite large, and extends into northern Baja California. Native plants know how to live here, and many of those that are adaptable to landscapes and home gardens can survive quite nicely with little or no irrigation. Some exotic (non-native) plants want climates with more warmth in summer, more chill in winter, or more rain through the year.
The best, as well as the worst, exotic plant species for local landscapes are those that are native to other Mediterranean climates.
The worst are those that are so happy in the local climate that they naturalize and become invasive to native ecosystems. Without pathogens or competing species that inhibited their proliferation within their respective native ranges, many naturalized species are detrimentally aggressive in ecosystems that they invade. Pampas grass, broom and Acacia dealbata are familiar examples.
The best exotics are not so threatening. Australian fuchsia, kangaroo paw, coprosma, westringia, bottle brush, grevillea, dracaena palm and eucalyptus originated from Australia. Lemon verbena, mayten and some salvias are from Chile. African iris, lily-of-the-Nile, bird-of-Paradise and all of the aloes came from South Africa. Olive, oleander, cistus, and all the lavenders are Mediterranean.
Highlight: Pittosporum tobira
A surplus of common names seems to be a common theme for many plants that we thought we knew the names of. The simple Pittosporum tobira, which might be known here by its Latin name, might instead be known as mock orange, Australian laurel, Japanese pittosporum, and Japanese cheesewood. Its native range is about as diverse, including Greece, Japan, Korea and China.
Back in the 1990s, the compact cultivar known as ‘Wheeler’s Dwarf’ was common enough to be as cliché as tam junipers were in the 1950s. There are actually a few other dwarf and variegated cultivars that do not share that reputation. Most are low, dense and mounding. ‘Variegata,’ although not a compact dwarf, grows slower and stays smaller than the unvariegated straight species.
Otherwise, Pittosporum tobira gets about 10 feet tall and wide. It can eventually get significantly taller, especially if lower growth is pruned away to expose the sculptural trunks within. If shorn as a hedge, it should not be shorn so frequently that the dense foliage is always tattered. Leaves are delightfully glossy and convex. Small trusses of modest pale white flowers are sometimes fragrant.
Horticulturist Tony Tomeo can be contacted at tonytomeo.com.