Sunday, February 03, 2008


What’s still green: Conifers, rose stems, yuccas, coral bell, sea pink, Saint John’s wort, yellow evening primrose, Mount Atlas daisy, some grasses

What’s gray or gray-green: Salt bush, winterfat, snow-in-summer, some pinks.

What’s red: Cholla, some pinks, small-leaved soapwort, coral and purple beardtongues, purple aster.

What’s blooming inside: Aptenia, geranium, kalanchoë; new leaves at top of dried coral honeysuckle stems.

Animal sightings: Small birds, usually alone, in the garden or along the fence.

Weather: Rain Monday, snow Tuesday, cold temperatures and intermittent high winds since; 10:35 hours of daylight today.

Weekly update: This has been one of those weeks that culls the weak and tries the strong. Monday’s rain fell on ground so soft my small car plowed 3" ruts in the drive. The next morning, northwest winds were too strong for me to close my front door from the outside. Since, night time temperatures have fallen to the low teens and the days have resoftened the drive. Even my neighbor’s arborvitaes have shriveled into themselves, turning their brownest faces to the elements.

In summer I look across the road at those evergreens with envy. The one near the back porch drip line has the pleated symmetry of party decorations that store flat, then open into honeycombed paper valentines or pumpkins. The younger two in front flourish with yuccas on the edge of a lawn he sodded in the center of his circular drive.

I’ve hesitated to plant my own, because someone in Texas told me they killed other plants, much like black walnuts. But I look at his vigorous shrubs and yuccas, and wonder what possible damage they could do here.

Anecdotes about plants’ bad habits are difficult to confirm. Where once writers followed standard etiquette that it was better to say nothing than say something critical, now publishers prefer subjects with product tie-ins. In either case, negative qualities were overlooked; if they couldn’t be ignored, plants were discretely dropped from texts. Information is left in the netherworld of rumor and the internet.

One reason for the confusion about arborvitae, commercially sold as Thuja occidentalis, is that it is commonly called white cedar. Red cedar, Juniperis virginiana, does suppress the germination of lettuce seeds in the standard test for allelopathy. Stipe and Bragg found it also inhibited or delayed the growth of finger coreropsis in unburned tall-grass prairies while Ferguson and Rathinsabathi found southern red cedar (Juniperis ciliciola) slowed red root pigweed and hairy crabgrass.

Neither cedar is actually a member of the cedar family; arborvitae is a cypress and the others are pines. The term cedar bark mulch can mean anything, and mulch is intended to suppress weeds. So the world of raw experience, unleavened by controlling theory or systematic experimentation, thrives.

Since I have no intention of growing lettuce - the local rabbits would be far more effective than any shrub in eliminating seedlings - it sounds safe enough to grow along a drive where only weeds and añil del muerto thrive.

However, now that I’ve learned a bit about white cedar, I’m surprised it grows here. Arborvitae’s native range is the Laurentian shield south through the Great Lakes where it thrives in swamps. There, it begins heavy seed production when it’s 30 years old and continues until it’s 75; it can easily live for another 300 years. If anything keeps it in control, it’s hungry white-tailed deer and bagworms.

Evidence from Alaska’s north slope suggests Thuja itself had evolved by the late Cretaceous, 65 to 97 million years ago, when limestone was forming. The genus still tolerates cold. In the wild, it can adapt to drought conditions, and its genetic structure has made it easy for nurserymen to create more than 100 cultivars attuned to different markets. However, the only thing I see I have that it likes is calcareous soil; my neighbor’s shrubs have certainly been highly offended by the recent cold spell.

Whether or not I experiment with arborvitae this spring depends on factors I can’t control: the amount of moisture left in the ground in the spring and the buying habits of companies that supply the local garden centers. One thing I can predict: I won’t be able to try southern red cedar mulch in the area where pigweed sprouts because the winds will blow it away within a week.

Ferguson, James and Bala Rathinsabathi. "Utilizing the Weed Suppression Capacity of Selected Tree Species in Weed Control in Woody Ornamental Species," Florida Nursery, Growers and Landscape Association report, available on-line.

LePage, Ben A. "A New Species of Thuja (Cupressaceae) from the Late Cretaceous of Alaska: Implications of Being Evergreen in a Polar Environment," American Journal of Botany 90:167-174:2003.

Nesom, Guy. "Northern White Cedar," USDA plant guide, 2003, available on-line.

Stipe, Dan J. and Thomas B. Bragg. "Effect of Eastern Red Cedar on Seedling Establishment of Prairie Plants," North American Prairie Conference Proceedings 11:101-102:1988.

Photograph: Neighbor’s arborvitae, 2 February 2008, growing under a drip line where household debris collects.

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