Set in stone

Stones are part of the earth's exposed skeleton, bones punching through its soft, verdant skin. Although they are most often used with water, plants and other landscape elements, many a traditional Japanese garden is stone alone, graded by aggregate size, ordered and raked to perfection.

Most of all, landscape stones reflect the native geology of a region, bringing its tall mountains and river banks into the domestic realms of our lives. And strangely enough, in a country where you can buy virtually any product from any part of the world, their inherent weight and the high costs of transportation keep large stones a local phenomenon.

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Stones of many origins Knowledge of a little geology will help make the choice and placement of stone a more enriched experience. We generally categorize stone into two fundamental categories: process of origin and method of deposition.

*Process of origin. Stone is created through one of three processes: fire/molten rock (igneous), deposition of particles in water (sedimentary) or re-formation through pressure or heat (metamorphic).

* Igneous rocks fall into two categories: intrusive, which are formed within the earth and later exposed by uplifting or erosion of surrounding rocks or soils, and extrusive, which are deposited on the earth's surface.

* Sedimentary rocks primarily form under water and from the particles of older, eroded rocks. This type is named for its relatively uniform particle size, for example sandstone, siltstone and mudstone.

*Metamorphic rocks, not unlike sedimentary rocks, are reprocessed forms of older rocks. Through either exposure to the inner earth's extremely high temperatures, or through subduction into depths of extreme pressure, these rocks become different and always harder than the original parent material. For a list of the more common landscape stone types by their process of origin, see the table on page C 6.

*Method of deposition. Whereas the processes of origin determine the structure of a stone, the way a stone is deposited will determine its immediate form.

*Solid-rock formations. Quarrying solid-rock formations yields angular stone of diverse sizes and forms, largely determined by the rock's origin and relative degradation. Most quarried stones of landscape value are intruded igneous ones, primarily granites. Although most quarried rocks come in angular, rough forms, landscapers often use cut and polished pieces in Japanese-style gardens as lanterns, water basins or as pieces of sculpture.

*River-deposited aggregates. River-deposited stones are the roundest ones you'll find. Large stones are a rarity in most aggregate mining operations; they generally are graded out of deposits and pushed to the side in favor of smaller gravels and cobbles, which are the priority mining products. Ocean-deposited stones also are well-rounded, but local agencies may discourage or prohibit collection within certain jurisdictions. Check before you collect stone on public beaches or lands.

*Field-deposited. Synonymous with many rounded rocks is the general name fieldstone, which varies with its process of origin. Most fieldstones have fallen off of adjacent mountains or are remnants of old volcanoes and lava flows. If you've driven down a country lane and noticed long lines of natural stone walls, their rural beauty most likely belies the challenge an early farmer encountered making a piece of land safe to plow.

*Volcanoes and lava flows. Old lava flows and volcanic eruptions produce porous rocks--primarily basalts--that time weathers into rounder shapes.

Designs for stone placement Most landscapers use landscape stone in a naturalistic format--loosely constructed, unobtrusive and, generally, surrounded by plantings or water. This loose format also lends itself well to stone walls or supports for elevation changes such as stairs, waterfalls, earthen berms and rock gardens.

Here are a few guidelines to help you place stones and achieve the individual setting you desire:

*Determine the top and bottom of the stone first. Depending on how they sit in a field, fieldstones develop distinctive tops and bottoms. The tops develop distinctive, sought-after patinas of lichen and mosses. Try to set them the same way they came out of the field, unless you want to convey the general image of option or balance (such as the Chinese symbol yin-yang). If you do, balance the setting so that a part of the underside shows.

*Convey active, kinetic emotions by using a long, angular stone and setting it disproportionately out of the ground on a strong, vertical axis, much like the stone figures of Easter Island.

*Convey passive, peaceful emotions by using rounded stone and setting them well into the ground or on a horizontal axis that mimics sleeping.

Setting landscape stone Setting landscape stone is an art unto itself, the purposeful goal of which is to make the stone appear as if Mother Nature had set them there--and this is no easy feat. To begin with, stone is extremely dense and heavier than it might appear when looking at specimens in a stone yard. A 2- to 3-foot diameter piece of granite can weigh 600 pounds. However, if you bury half of it in the ground, you may be disappointed with its diminished visual weight.

Here are a few steps you might follow in setting stone into a landscape:

*Allow the overall design of the landscape determine the type and form of stone you desire.

*Select the stones in the field, stone yard or landscape supply center, and make arrangements for delivery.

*Dig holes of approximate size on site and lay out the best delivery-access paths. If the stone locations are in the middle of softer landscape soils, forklift delivery may be impossible. You will more likely need a crane.

*Determine the method of delivery based on the size and weight of the stones. You'll generally get lighter stones delivered by truck and then either unloaded by forklift or hydraulic arm. A delivery operator will probably use a crane if stones are large. It is critical to preserve each stone's natural beauty and avoid damage during delivery. Using fabric slings and wooden palettes is preferable to chains.

*Place stones in their respective holes as close to their final, desired configuration as possible.

*Plan to achieve your final settings by using heavy iron bars and wooden blocks to leverage the stones into the final configuration and relative elevations.

*Backfill the stones with landscape soils once you place them. Plant ornamentals or surround the stones with final surface treatments, such as paving, raked gravel or water.

Take advantage of other information sources To learn more about stone and its many uses in the landscape, many resources are available. You could begin your research through the internet, the Yellow Pages or the geology department of a local college or university. A visit to various local gardens or an arboretum with Oriental collections offer ideas. Your local library may have nature and geology guides for your region, or a section of books about Oriental gardens. A Japanese Touch for Your Garden, by Seike, Kudo and Engle, has numerous photographs of stones and a chapter on designing stone groupings.

Steve McGuirk, ASLA, is a landscape architect at Madrone Landscape Group (Soquel, Calif.).

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