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The Dry Garden: Trees shed their winter coats

June 11, 2010 |  8:21 am


Bark_manzanita Bark hides in plain sight. Who needs the superhero power of invisibility when you’re constantly upstaged by flowers, fruit and foliage? It takes an event to draw the distracted eye to the trunk and limbs of a shrub or tree.

That event is happening now. With the summer solstice nigh, California’s best-adapted woody plants are slipping into dormancy to ride out the dry season. As they do so, still sated on spring rain, newly thickened by another year’s growth, the most wanton of the lot are shedding last year’s bark.

“It happens right at eye level,” says Santa Barbara horticulturist Carol Bornstein. Perhaps the most noticeable example, she guesses, is the flaky habit of the California sycamore, whose shedding pattern she describes as creating a “gray-on-white jigsaw puzzle.”

Those who have witnessed the molt of either our native madrone tree (Arbutus menziesii) or its Mediterranean variant (Arbutus unedo) are not likely to forget it. The sloughing of their mahogany bark amounts to such a show that when it came to landscaping around her own Mar Vista home, Los Angeles garden designer Marilee Kuhlmann planted an Arbutus tree called Marina in front of a window, pictured above right, with a view straight out onto the wood.

Bark_myrtle

If mottled pinks and mauves in a tree trunk are more your thing, then Bornstein recommends the crape myrtle tree, right.

“Because it’s deciduous, the beauty of the tree’s bark is a particularly nice feature.”

The crape myrtle’s cousins commonly grouped as guavas all have good bark too. 

Those who plant the apple guava (sometimes called common guava or tropical guava) for winter fruit to serve with lime and salt will still gaze fondly at the tree, as in summer it begins to shed its silver bark, almost like a sycamore.

The even prettier orange wood of pineapple guavas is often hidden by foliage because of the plant’s bush-like tendency. But they can be trained into small trees.

For those who like bark that positively unravels on a trunk, Bornstein recommends Catalina ironwood. Perhaps in a pan-Pacific spirit, the bark of many species of eucalyptus, the most common of Australian natives used in California, do this as well.

Yet notable bark trees aren’t always basket cases or strippers. Bart O’Brien’s mind kept coming back to the green limbs of the Sonoran Desert’s palo verde trees. The Rancho Santa Ana Botanic Garden horticulturist has a point: It’s not every tree whose limbs can photosynthesize when it is too dry for the plant to sustain foliage.

Bark_1420

Before moving to shrubs, no discussion of characterful tree bark is complete without talking about oaks. California has many cork oaks imported from the Mediterranean. The trees are so well endowed that they can survive the harvesting of their bark. Yet it is the far thinner bark on the native coastal live oak, right, that often creates confusion. In trees of the same girth and age, the bark of one might be deeply furrowed with long brown-hearted fissures while the bark of the other might be smooth and silver.

“That’s genetic variation,” O’Brien says. “That species is really quite variable. You have the two extremes, but if you really start looking at them, you’ll find all kinds of intermediates.”

If only stretch marks looked so good on human skin.

Distinctive bark happens with the same frequency in shrubs. Mountain mahogany’s open habit allows a clear view of its almost purple limbs.

Bark_1411

The early summer shedding of manzanitas revealing orange under-wood is so gorgeous that the loved garden cultivar of Arctostaphylos densiflora called Howard McMinn, shown at left, is often pruned in a way that reveals the trunk.

This is not to encourage fetishists. Plants need their leaves. Unless you have a single-trunk elderberry bush, it’s probably best to forget pruning it to create a tree. Better to admire the wood as this goes from green to red to a handsome shaggy brown during early autumn thinning.

Dwelling on the beauty of bark without going into the biology of its production, or health value for the plants and us (aspirin is a bark product) may leave some frustrated. Just so I can say I said it, and to spare others writing in, please, please, please prefer telephone poles when stapling or, worse, nailing up signs.

While these other points about bark stay relevant all year, the fleeting spectacle of our native plants slipping off their coats for summer is happening now. There could be no more theatrical reminder of the variability, texture and sheer beauty of bark, or incentive to highlight it when designing a garden.

-- Emily Green

Green's column on sustainable gardening appears here every Friday.

Photo credit: Emily Green

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