Gardening physics

24 June 2009

In The Garden With the Fluvanna Master Gardeners
By Irene C. Burke - Fluvanna Master Gardener
Fluvanna County Extension Office: 434.591.1950

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The World Book Dictionary says that physics is "the science that deals with matter and energy, and the action of different forms of energy... Physics studies force, motion, heat, light..." For todays garden discussion, lets plan for the seasonal force and motion of wind and water on steep slopes.

Weather

As you study storm patterns, notice where water flows, where the wind goes, what bends, what breaks, where the rose petals scatter. This will help you select and place plants, which defend themselves well against such perils.

Basic principles

Most but not all wind sources in the Virginia piedmont are westerly. Wheres your exposed western slope?

Wind gusts must be slowed, not stopped, because when stopped by a solid barrier, the tempest will rise to the rim then scoop down the leeward side and scour whatever is there.

On planet Earth, water still flows downhill, the steeper the slope, the greater the force, especially over naked land.

Landscape strategies

A few low-maintenance tactics should help prepare the terrain for these dynamic forces: trees, shrubs and groundcovers that filter or absorb the impact, that drape tenaciously along slopes, that promise easy care after establishment, and are mostly natives.

Strategy 1

Use a vertical permeable barrier of curved, staggered plant groups of moderately spaced trees and shrubs to slow the winds course along the site, whether oblique or full on. Under plant with ground covers or apply mulch.

Strategy 2

To counter gravitys pull, begin planting at the top of slopes, no matter the strength or depth of roots or the arc and reach of vines and stems.

Strategy 3

Leave lawns for flat areas since water will cascade rapidly over the most thickly growing turf.

Strategy 4

Mulch heavily with a sandwich layer of 1" compost followed by 3" wood chips topped with more attractive 2" pine or hardwood bark, or less expensive shredded leaves. The compost provides nutrients while the next two layers anchor as they decay into the soil.

Strategy 5

To keep pruning chores to a minimum, space according to mature size. Interplant with small-sized bulbs or simply mulch.

Strategy 6

Avoid lines of plants by clustering in odd-numbered collections. Otherwise youll create landscape boredom and an unwelcome panel of shade on both sides with its separate issues. Strive for a harmonious mix of shapes and sweeps of feathery curves and broad based triangles.

Strategy 7

Stone or wooden terraces are like earthen dams and landfill liners: they will eventually fail; in downpours, water cascades over them and they always need maintenance. Our goal is minimal care and terraces dont fit with that goal, thick, manageable vegetation does.

Trees, shrubs, groundcovers

These few candidates abide the squalls, on the crest and on the windward side of a slope: Trees---American hornbeam, amur maple, arborvitae (pyramidal and oriental), dawn redwood, Japanese pine, junipers, river birch, yews; shrubs---broom (cytisus species), forsythia, Japanese barberry, lilac, mock orange, privet, pussy willow, quince (chaenomeles species), tatarian dogwood, viburnum; ground covers---cinquefoil, lavender cotton, liriope spicata, sweet William, winter jasmine, yarrow.

Tip of the Week

According to Janet Raloff in the May 28, Science News "A new study links two weed killers with pancreatic cancer in pesticide applicators and their spouses", pendimethalin and EPTC, even when using protective gear. If you apply weed killers perhaps that's not all you're killing. Try a full strength solution of 5%-9% strength clear vinegar, mulch, hoeing and hand pulling.