Peeling Bark

In a not uncommon response to summer-dry heat, a number of trees and shrubs shed their bark in the middle of the summer.

Summertime bark break, Manzanita, Arctostaphylos

In California, this exfoliation seems to happen almost instantly in Madrone (Arbutus menziesii) and many species of Manzanita (Arctostaphylos) with great delight to any observer who watches these natives with any regularity.

One day a walk in the dry woods, the always beautiful red-mahogany bark will be split open, as the bark rolls back and the girth expanding just that much more.  In manzanita the bark will curl back in neat tight curlers.

Manzanita – Summertime Bark break, exfoliating

Madrone seems to come off in ribbons.

Madrone, Arbutus menziesii – Summertime bark break

Both of these genus are well adapted to summer-dry conditions but one must be careful to match the right species to the right microclimates. Manzanita are native to many parts of California and gardeners would do well to check with local nurseries, or if you are lucky enough to be in California, check in with your local native plant society chapter to find the best ones.

In nature Madrone are found in dry sloping conditions often in the company of taller Bay and Oak trees, and usually need just the right soil mycorrhizal relationships to thrive.  Gardeners might consider the Arbutus unedo, a mediterranean native, more adapted to garden conditions.  The bark is lovely and the large fruit are highly ornamental but you don’t get the exploding bark.

Madrone – Summertime bark break

Arbutus

Arbutus unedo 'Elfin King' (Strawberry Tree) with fruit.

Arbutus unedo ‘Elfin King’ with fruit.

With evergreen, leathery, dark green leaves, showy clusters of tiny white spring flowers, small red berries in fall, and red-brown peeling bark, Arbutus menziesii is a signature tree of western North America.  Native to coastal evergreen forests from southern British Columbia to California, the western slopes of the Sierra Nevada, and the eastern slopes of the Coast Ranges, this tree has long been considered too difficult for most cultivated landscapes.  Commonly known as Pacific madrone, A. menziesii is available in small containers mostly from specialty nurseries and at native plant sales.

For best results, Arbutus menziesii should be set out in its permanent spot when the seedling is a foot or so tall.  Excellent drainage is essential.  Young trees seem to prefer the filtered shade of evergreen trees, but may not establish in full shade. They thrive in full sun along the coast and inland at higher elevations.  Water only to establish and do not fertilize.  Water and fertilizer will promote growth but make this plant more susceptible to disease.  Usually slow-growing to anywhere from fifteen to fifty feet tall, trees may reach over 100 feet at great age.

Arbutus unedo (Strawberry Tree) by gravel pathway with ornamental grasses in David Fross waterwise sustainable garden

Arbutus unedo (strawberry tree) by gravel pathway with ornamental grasses

Arbutus unedo, strawberry tree, is native to the Mediterranean Basin and parts of western Europe.  With evergreen, leathery, dark green leaves, drooping clusters of small rosy white flowers, largish red fruits, and peeling reddish brown bark, strawberry tree is similar in many ways to Pacific madrone but much more tolerant of garden conditions. It grows in sun or shade and most soils and accepts some summer irrigation as long as drainage is adequate.  Where content, it can reach fifteen to thirty feet tall and almost as wide.

Cultivated varieties of Arbutus unedo are common in the nursery trade. ‘Elfin King’ is a compact shrub with denser branching and somewhat slower growth than the species. ‘Compacta’ is said to be similar, reaching six to ten feet tall and wide at maturity.

Arbutus ‘Marina’ is a fairly large tree (forty feet tall and thirty feet wide at maturity) that looks enticingly small in fifteen-gallon containers.  You will see it planted five feet from a building wall in new landscapes.  In such situations you can be sure it will outgrow its allotted space and over time will require quite brutal pruning or removal.

‘Marina’ is often promoted as a garden-tolerant equivalent of Arbutus menziesii, and it is somewhat more accepting of typical garden conditions – a bit of summer water, less than perfect drainage, and clay soils.  But it won’t take as much abuse as commonly assumed, especially excess irrigation or poorly drained soil.  It is also best planted in a spot that can feature rather than fight the shedding of bark, fruits, and large leaves, which, as with most strawberry trees, is pretty much continuous.

California buckeye

Aesculus californica, California buckeye tree in winter with bare branches at East Bay Regional Parks Botanic Garden, Berkeley.

Aesculus californica, in winter, at East Bay Regional Parks Botanic Garden, Berkeley.

California buckeye (Aesculus californica) puts on a bold and fascinating seasonal show.

In late winter bright apple-green new leaves burst forth at branch ends and rapidly unfold, quite suddenly claiming the stage among the darker greens of evergreen oaks, bays, and pines.  In spring to early summer showy spikelike clusters of lightly fragrant creamy white flowers are held gracefully upright above the leaves.  The large polished-brown seeds peeking through leathery, pear-shaped pods are highly decorative on silvery gray branches in fall.

Flower head of Aesculus californica - California buckeye tree

Aesculus californica flowers

Native to much of California on dry slopes, in canyons, and along waterways, California buckeye needs no summer irrigation once established, though trees will respond to heat and drought by dropping leaves.  It’s hard to be fully prepared for the large palmate leaves to turn pale yellow, droop sadly on the tree, and drop in what seems to be high summer.  Occasional deep soakings may help keep leaves on the tree a little longer in coastal areas.

California buckeye grows 15 to 35 feet tall and spreads more widely.  Form is best in sun, where trees develop into a living sculpture of multiple or low-branching trunks, symmetrically outstretched branches, and a delicate tracery of small branchlets.  Trees thrive in part shade but may be awkwardly shaped and rangy. Good drainage is appreciated.  Deer will browse the leaves.

Aesculus californica-California Buckeye in fall fruit

Aesculus californica fruit

In years of normal rainfall, the heavy seeds sprout and establish themselves pretty much where they fall, unless they roll downhill or are carried away by water.  They can be moved before the large whitish root finds its way into the soil.  Plant with the root covered by soil and the seed at least partially exposed.  Keep soil lightly moist until new growth is decisively underway.  Water for the first year or two, especially if winters are dry.

California Native Redbud Tree

holt_433-177.tifI hear from long-time residents of Amador County, California, that our native redbud (Cercis occidentalis syn C. orbiculata ) is not found anywhere in that county except where planted.  To me, this is a fascinating mystery, as it is commonly reported by reliable sources as occurring in the wild in that part of the state.  Some have suggested it may be the soils, that redbud requires “ultramafic”  (basic) soils, even serpentine, that are not common in Amador County.  If you live in that part of the world, please let us know if you have seen this special plant in the wild and exactly where. Continue reading