Botanica Atlanta | Landscape Design, Construction & Maintenance

Images: Mark Wheadon & Diamond Geyser

If you imagine a wall, there is a good chance that your mind goes to mortar. Mortar, considered all but compulsory on brick and stone buildings in the modern world, certainly has its advantages. Mortared walls are firm and fixed; crisp and refined; and can readily support such attachments as swinging gates and light fixtures.

Images: Jon Hill & Diamond Brooke

It is worth noting that -- when you are building a landscape wall of brick, block, stone, or even wooden masonry units -- you have a choice. Selecting a "dry stacked" or "dry laid" wall has some distinct advantages.

Images: Karl Norling & Anthony Tong Lee

First off, with nothing to "glue" the wall units together, there is flexibility for some amount of movement. In essence, the open joints can absorb soil settlement without noticeably cracking but also without requiring the construction of an expansion joint.

Images: Duncan Cumming & Bart Lumber

The reason that cracks do not emerge in a dry-stacked wall is that deep, shadowed joints are simply part of the design. With lower expectations for formality and precision, dry-stacked walls require shallower, simpler foundations, and often all that is needed for a solid base is to bury a few inches of the first course below grade. Weep holes, required for through-drainage in concrete and mortared retaining walls, can also be omitted due to the loose structure of a dry-laid wall.

Images: Sonja Lovas & Robert J. E. Simpson

While there is a lower baseline for craftsmanship with a dry-stacked wall, the level of care, experience, and creativity that goes into one of these walls is easy for anyone to detect. The most impressive and durable dry-stacked walls are built by old-school craftsmen, often with a great degree of laborious tooling, chinking, and brainpower. A builder who is both creative and skilled can tailor a dry-stacked wall to harmonize with the landscape and nearby architecture; walls can take on an ordered ashlar pattern or incorporate large boulders and small pebbles into an organic composition.

Images: John Seb Barber & Rick Payette

At the bottom of the heap - in terms of stability, craftsmanship, and cost - is simply a linear pile of rubble. With a range of options, it is critical to reflect on the purpose of any new walls in your landscape. Do you need a perimeter wall for safety or security? Are you trying to hold back the sea or just keep your pets on your property? Do you need a wall or just a visual border? Ask yourself these questions before laying the first stone.

Image: Al Crompton

Image: Alleys of Seattle

Take a moment to glance at the photograph above. It is easy to see both character and age in these materials, but while it is pretty clear that this is a time-worn pavement, it might take a bit longer to realize that these are not stone cobbles.

Across countries and centuries, stone, brick, or poured concretes are the mainstay choices for exterior, at-grade pavements such as roadways, sidewalks, and paved patios. But one quirky exception -- wood paving -- should be noted for its unique merits.

Images: ForgottenChicago and Slvrmn

Examples of wooden pavement are rare, but they still can be found scattered around the globe. One historical example can be found in mid-nineteenth century Chicago, where wood pavers were installed as significant upgrade to Chicago's existing dirt roads. Using the Nicolson Paving System, many of the city's roads were covered in wood blocks to make them cleaner, safer, and still relatively quiet for carriage traffic. It seems apparent that at that time, issues of availability were a deciding factor in the selection of wood, which Chicago's civil engineer explained when he said, "Wooden pavement(s)…have great advantages in a city, where suitable stone was scarce, where lumber was the great staple of the market."

Common sense tells you that for any of its advantages, wood has significant drawbacks as a pavement material. Lacking the hardness and durability of masonry materials, wood is certainly more prone to degradation from wheel, hoof, and foot traffic, and it is obviously quicker to rot. In Chicago, Nicolson slowed rotting through the application of creosote, which you probably know as the tar-like substance that seeps out of railroad ties and telephone poles this time of year.

Images: Emily Long, Ryan Wilson, and Nancy Regan

A recent project has rehabilitated one of Chicago's last remaining stretches of wooden paving. Wooden Alley, listed on the National Register of Historic Places, was restored, and by selecting naturally dense and durable black locust timber, the use of toxic creosote was avoided.

Images: J. McConnell, Gabrielle Marks, and Brigitte Reiser

If you are seeking a paving material for a garden terrace, patio, or pathway, do not be too quick to dismiss wooden paving as an option. Depending on the needs of the outdoor feature, wood blocks might be a perfect material choice. It is lightweight, affordable, easy to install, and has the hidden advantage of developing a rich,

aged patina much more quickly than stone or brick.

Image: ForgottenChicago

Image: Prospect Contractors

From the road, there's usually not much to love about them. Gabions, wire baskets filled with rocks, are most typically used to stabilize transportation and engineering projects or to fortify military installations. If you have noticed this method of construction before, you likely could tell that loose pieces of stone had been packed into a wire-mesh box; understandably, the word "gabion" originates from the Italian word for "cage."

In most applications, gabions seem drab and utilitarian, and they may seem no more fit for your garden than a highway Jersey barrier. However, in some places, designers have resuscitated this construction technique, imagining new forms, materials, and details that are sometimes quite inspiring.

Images: Only Lines, Cherie Xiao, & David Harvey

Earlier this year, I was fortunate enough to see some truly enterprising gabion applications in the two Australian cities of Sydney and Canberra. Rather than being relegated to the roadside, gabion installations are nearly as commonplace in Australia's gardens, parks, and plazas as they are along its highways. This is largely justified, though, as these garden gabions tend to be designed, detailed, and dressed for the occasion.

Images: Sam Valentine

Considering they are assembled from some of the hardest, coldest materials available, gabion walls, steps, and slopes can take on a surprising amount of softness and life. The malleability of wire allows for curves and smooth shapes just as easily as it creates crisp, orthogonal cubes. Because of their unique abilities to brake water velocity, allow free draining, but still hold together structurally, gabions are regularly used to restore river banks and stabilize eroding hillsides. Choosing gabions for streams and slopes often leads to a beautiful side effect: over a period of years, the crevices and voids fill with soil and sediment and -- ultimately -- bountiful vegetation.

Images: Denver Aquino & Lauren Jolly Roberts

Image: Ken McCown

Images: Scott MacLeod Liddle, Thomas Roland, and Joanne Richardson

ὁ δὲ ἀνεξέταστος βίος οὐ βιωτὸς ἀνθρώπῳ

It was 2,400 years ago that Socrates is said to have taught the above words, and though you may not be any more up on your Greek than I am, the meaning of his words still translate into truth today. "The unexamined life is not worth living for a human being," or -- to reframe it in a slightly kinder light -- "Life is more enjoyable when we carefully consider the details."

Masonry is a universal construction technique used to build everything from shelters to garden walls to horizontal pavements. Masonry "units" can vary widely to include stone, brick, concrete block, glass block, tile, and even timber, but what unites all masonry structures (literally) is mortar.

Images: Don Shall, Je Kemp, Theilr, and Rachel Towne

The most common mortars, at least since Socrates' time, consist of three basic ingredients. Sand, the main ingredient, is inert on its own, but when it is mixed with cement and water, the ingredients react to form a paste-like binding mixture that can be applied to brick, stone, and other rigid surfaces. Mortar hardens to a rock-hard state after it is applied, and by laying it between masonry units, it serves to "glue" the structure together, evenly distribute the structural load, and create weather-tight joints.

Images: Lucidio Studio, Maryland Architecture, Planning & Preservation, and Rich Bettridge

Many of the ways in which masonry garden walls can vary are obvious. Even beyond the different masonry units that can be selected and the colors that are inherent to these materials, wall surfaces can take on a variety of forms and alignments. Beyond these more noticeable design decisions, however, is the fine-grain design of the mortar joints. Jointing is one aspect of masonry that is often the last design element to be considered -- if it is considered at all.

Even with the identical structural and weatherproofing considerations satisfied, there is a surprising palette of mortar joint profiles, each with its own aesthetic and historic associations. Joint lines may seem like a trivial detail to some, but considering the design "between the lines" can bring a level of richness and refinement to your landscape that cannot be found in most built environments. From flush to concave and beaded to raked, envisioning the most appropriate jointing for a garden masonry structure is an opportunity that is best not neglected. After all, sometimes the unexamined garden is not worth visiting.

Image: Simon Bisson

Masonry, by its most universal definition, is a method of building that involves assembling individual units and binding them together with some type of mortar. A brick chimney. A tile floor. An ancient stone wall. It is not hard for anyone to call to mind several examples of masonry construction.

Images: Esparta Palma, Elliot Brown, and Kavjin

For good reason, the materials that are traditionally selected to serve as masonry “units” match the mortar in terms of durability and organic content. Whether they are chunks of rock, ceramic pieces, or sun-dried clay bricks, the most desirable building blocks are inorganic so they will not rot and mineral-based so they can stand up to the elements.

Mankind, though, is not always blessed with the ideal resources for such construction techniques. Sometimes we simply have to work with what we’ve got.

Image: Syzygy Salvage

Cordwood masonry has gone by countless names, including log-butt, stackwall, stovewood, and even “Depression building” construction, but its penurious nature leads me to believe that this mode of building was more often than not employed without a formal name. Cordwood masonry sprang from basic necessity in places where humans needed to build shelter, had a decent supply of mortar, but lacked a resource for inorganic building blocks. Rather than use brick or stone, cordwood builders use short logs – much like what you would put into a crackling fire – between the mortar joints. Some believe that the earliest instances of this building method were born in the 19th century in central Wisconsin, where ancient glacial movement had left generous deposits of limestone (the first ingredient of lime putty mortar) but little more than cedar forests for masonry units.

Images: Paul Comstock and Akkodra

In more recent decades, cordwood construction has seen something of a revival. Celebrated for its earthy aesthetic, its flexibility of form, and its moments of unparalleled, beautiful detailing, cordwood masonry has been brought into a modest renaissance by Rob and Jaki Roy, who have centered the movement from Earthwood, their Upstate New York property. As of July 2012, there were an estimated 1,500 existing cordwood homes (with more than 200 more under construction) in North America alone. The Roys and others offer regular workshops, books, and videos to promote this unique architectural style.

While not everyone might jump at the chance to live in such a rustic, unconventional structure as a cordwood house, gardeners everywhere should consider incorporating cordwood masonry techniques into their landscape projects. The materials are inexpensive and readily available, the techniques are easy to master, and in the mediums of wood, glass bottles, and mortar, a gardener’s creativity can truly thrive.

Images: Paul Comstock and Tony Cenicola/The New York Times

Author: Sam Valentine, BLA, LEED AP

My goal in last week’s post was to give the reader a clear understanding of wrought iron: its history, composition, and unique aesthetic value. This week I will shine the same spotlight on another type of iron that is often mistakenly described “wrought.” The focus of this article is cast iron.

Images: Stephani Bachman and Cattoo

I admit that it is somewhat strange to think about cast iron as a “new” technology, especially as its first appearance for structural purposes roughly coincided with the birth of our nation. In the scheme of things, however, iron has been with us for several thousand years, and we have only known how to efficiently cast it for a few centuries.

The development of the cast iron process was a huge leap in technology. Whereas every single component of a wrought iron structure had to be heated until red hot and then laboriously hammered, twisted, or bent into a desired form, the technique of casting iron is comparatively simple. Only one original object – a fence post, a manhole cover, or a frying pan – needs to be created. From an original, heat-resistant molds are then made, and finally, molten iron is repeatedly poured into these molds and allowed to cool, thus replicating the original form over and over again. For this reason, the casting of iron was as much of a breakthrough to metalwork as the development of the printing press was to the written word.

The trick, the only thing that had hindered this process from coming around sooner, was the availability of lots of coal and the design of a furnace that could get hot enough to liquefy iron.

It was in the late 1770’s that perhaps the first large-scale iron structure was built near a town fittingly named "Coalbrookdale." This structure, known officially as “The Iron Bridge,” was constructed by several trailblazers in furnace technology. The bridge was built to span a 200-foot gorge, and though it was completed in 1779, it still stands today.

Image: Phil Parsons

Cast iron structures are modular; they could be put together from a repeating combination of prefabricated components. At that time, bolts were not common place, so the cast iron was fit together much like wood joinery, which was the only structural precedent the builders had to look to at the time.

Images: R. P. Marks and Pete Reed

Like wrought iron, the aesthetic and stylistic properties of cast iron have been influenced, if not defined, by the process that makes them. The repeating cloned process is capable of capturing intricate details and complex patterns that a blacksmith would dread hammering, and it almost always does so without monotony, as I have never seen a cast iron fence that I found monotonous or boring. It is in this detailing that a piece’s quality becomes apparent. When compared to modern, off-the-shelf cast iron patterns (which, these days, are actually more often hollowed steel or even aluminum) there is a major gap in richness. When comparing fences, they seldom have the sturdy, hefty posts and detailed bevels, motifs, and forms that were incorporated in cast iron fences up until the middle of the twentieth century.

 Images: UGArdener and Torrey Wiley

Whether cast or wrought, ironwork has a considerable impact in the landscape. In both residential and urban settings, this material, and the many shapes it can take, states with pride that it is of an earlier time. Sometimes it is stated in the sense of style or craftsmanship, detailing done in a level of quality and skill that has been all but lost. Other times the age of the piece can be biologically determined, by looking at a century-old tree trunk that has fused itself into the rails and pickets of a fence.

The tree, of course, yielded to the metal frame of the fence because it is a growing organic organism, but I feel that this phenomenon serves as a symbol in the landscape. Just as this grotesque growth proves that the fence predates the centenarian tree, it will likely outlive those people that have enjoyed its beauty. Ironwork lends character to a landscape by speaking to a visitor in a language that is rare, but understood by all. In the landscape ironwork speaks of an earlier time.

Image: Peter Hawman

By Sam Valentine, BLA, LEED AP

 Image: Andy Coan

Take a walk through the streets and gardens of Savannah, Beacon Hill, Georgetown, or New Orleans, and you cannot help but notice the subtle, structural beauty of ornamental iron. In historic fences, lampposts, balcony balustrades, and even boot-scrapers you will find this classic, dark material pounded and molded into various shapes and done so in a range of styles.

Both wrought and cast iron have great aesthetic value in the landscape, but the differences between these two materials should be properly recognized. Their titles are often used interchangeably, but in this week’s and next week’s posts I will try to clarify these two distinct materials, as well as highlight the unique strengths and limitations associated with each material.

Images: Tristan Savatier and A.B. Mann

Mankind began working with wrought iron thousands of years ago, and its importance should not be understated. Wrought iron gave the Roman’s spears, medieval knights’ swords, and revolutionary colonists’ rifles. The material also formed fasteners and fittings for the ships that allowed Europeans to explore and ultimately conquer the North American continent, and it produced the horseshoes and wagon axles that enabled American settlers to move west across the continent.

The iron alloy that was heated, hammered, and cooled to make up this wide variety of objects has a low carbon content and a high presence of slag. These fibrous slag inclusions not only give wrought iron a visible “grain,” similar to that of wood, but it also makes the material less prone to rusting than many other iron alloys. Perhaps the best demonstration of this quality can be seen in the Iron Ashoka Pillar in Delhi, India. The twenty-three foot tall, six-ton pillar is reportedly made of ninety-eight percent wrought iron, and archaeologists and metallurgists hypothesize that it is this chemical composition that has kept it intact even after 1,600 years of exposure to the elements.

Images: Ryan Gallagher

So how can you distinguish wrought iron from its sibling, cast iron? If you know what to look for it is actually quite easy. When you inspect a piece try to imagine if its form could be created by heating and then hammering, twisting, or otherwise warping an iron bar. On the other hand, anything that looks carved or molded, especially reliefs seen in floral-themed medallions or agricultural-inspired motifs, is probably cast iron.

Images: TheFadedPast, Bob Segal, and Sam Valentine

Wrought iron reached its heyday in the mid-nineteenth century, but after the 1860’s it began to fall in popularity as cast iron and steel became more easily attainable. The amount of objects that are made from wrought iron today is quite small, which is due to both a limited supply and the custom nature of installation. However, as a quick Google search will show, there are many off-the-shelf, mass-produced products that still falsely claim to be “wrought iron.”  

Other than historic cases, there has been very little wrought iron work done in the last fifty years. A notable exception to this rule is the work of metal sculptor Albert Paley. Though he has worked in many metal media – gold, bronze, Cor-ten steel, and stainless steel – it is his work in wrought iron that I find most captivating. Paley employs the same techniques that blacksmiths developed for millennia before him, but he gives it his own twist. As a result, his work is both unmistakably wrought but undeniably new.

Image: Joseph Watson (Sculpture by Albert Paley)

Next week, I will go into a similar amount of detail on cast iron. In the meantime, please tell me if there are any wrought iron structures that you especially admire. Also, if you have any questions about the distinction between the two materials, please ask in a comment below.

Author: Sam Valentine, BLA, LEED AP

Even a speck of common sense tells us that the shortest way to get from one point to another always takes the path of a straight line. Following a meandering road that zigs left and zags right is surely less efficient than taking a direct route. We hold these truths to be self-evident.

Images: Goat Mountain and S. Cholewiak

When you encounter a serpentine brick garden wall – also called a “crinkle-crankle” or “ribbon” wall – it is natural to extend this same logic and deduce that the winding curves are as equally inefficient as a meandering path. You may also observe that, despite this apparent structural inefficiency, a curving wall has several aesthetic advantages to a straight brick wall. The wave-like form provides visual interest, lends a soft edge to an outdoor room, and creates a rhythm of pockets that can be used for ornamental planting and sculpture.

However, when you carefully study them, you might realize that these walls are deceptive structures. Contrary to its inefficient appearance, a serpentine wall actually requires fewer bricks than a typical garden wall to withstand toppling. Due to the indirect footprint they follow, serpentine walls are in fact longer, but because they can be built to a thickness of only a single brick they are ultimately more economical. The looping, playful footprint actually serves to reinforce the structure and keep it from tipping.

Engraving by Peter Maverick (1825) from Thomas Jefferson’s plan

Years after he authored the Declaration of Independence, and served as our country’s first Secretary of State, second Vice-President, and third President, Thomas Jefferson incorporated serpentine walls as a dominant feature of his design for the University of Virginia. His historic nineteenth-century plan for the campus indicates rows of buildings fronting onto a rectangular quad, and each of the building’s rear yards is enclosed with garden walls. If you look closely at the plan you can discern the squiggling lines that represent these serpentine walls.

Images: S. Cholewiak and UGArdener

Though the aesthetic of this type of wall is not appropriate in all landscapes, I find that the undulating edge condition created by a serpentine wall can complement some garden spaces much more nicely than the straight lines of a typical wall. A few states south of Jefferson’s garden walls, a beautiful example of serpentine walls can be seen at the University of Georgia’s Founders Garden, which is named for the twelve founders of the Ladies’ Garden Club of Athens, the first garden club in the United States. Only a few steps from the classrooms and studios of the country’s largest landscape architecture program, two vine-covered garden walls snake their way through lush planting beds and lend soft edges to the formal lawn space.

Meandering roads are never the shortest, but they often provide a more pleasant, scenic experience. In the case of the serpentine wall, gardeners can discover a tool that is historic, economical, and offers great aesthetic potential.

Image: Goat Mountain

Author: Sam Valentine, BLA, LEED AP

Sinkholes, those frightening depressions that appear suddenly in your yard after major rain events, are popping up (perhaps we should say dropping in)  in neighborhoods all over Atlanta and homeowners may be faced with another hazard of recent torrential rains along with flooded basements and crawl spaces, fungal diseases in the landscape and downed saturated limbs.  Whether caused by natural or manmade means, sinkholes must be addressed to maintain a landscape's safety, functionality and beauty.

Source: USGS

Georgia and Florida inherently have natural sinkhole tendencies due to a high percentage of limestone in the substrata.  Limestone is a soft rock and over time underground water movement and geological movement can erode the stone into a semi-solid status.  Heavy rains in turn cause settling of top soil in the spaces created by the reduction in limestone mass.  These are often imperceptible changes however there is great potential for a notable soil depression.

Manmade causes are also common.  Construction debris buried on site frequently leads to sink holes if the builder did not ensure proper grading and soil compaction before selling the property.  Broken water, sewer or gas lines can also create sinkholes.

Before you can properly repair a sinkhole you must first figure out what type of sinkhole you have and how big it is.  Dig beneath the sinkhole at the lowest point, and dig wider than the sinkhole to explore the cause.  If you encounter debris, you have a void that can be resolved with the help of a landscape professional. If you encounter limestone or granite bedrock, broken pipes and or water, you may want to get a city or county authority involved.

For the manmade sinkhole which is less than 3 inches deep, apply topsoil in a 2:1 mix ratio with sand.  Existing grass will grow through this easily or you may choose to seed if there was no lawn above the sinkhole.  Do not seed if there is existing lawn.  If the sinkhole is greater than 3 inches deep, remove the sod carefully, then apply topsoil and compact using a compactor and finally, replace the sod.  If greater than 1 foot of topsoil is required, compaction should occur once per foot of new soil.

If the sinkhole is a natural, substrate problem, remove all organic matter and debris and fill the bottom of the hole with rocks in graduated sizes from large at the bottom to gravel.  Apply landscaping cloth, then cover with sand until level with the top of the subsoil.  Compact, then add topsoil and compact.

Unless your sinkhole is small you should probably have a landscape professional help you assess the problem and suggest solutions.  If you encounter standing water or smell gas, call your city or county authority as well.

Atlanta recently got over 25 inches of rain and many residents experienced the ravages of our floodwaters in some way or another. High volume preciptation created problems with both pooling water and fast moving water, both problems that can be managed in the landscape.

Site grading is the most elemental of drainage strategies homeowners can use to control the flow of water across their properties from areas of undesirable over-saturation to collection areas for later use or to municipal stormwater systems. Generally houses should be sited so that stormwater drains away from the house.

If downspouts create pooling or erode the soil, or if high volumes of water enter from a neighboring property, dry creek beds can be used to direct rainwater off the property or to a collection area such as a dry pond, retention pond or rainwater harvesting cistern. Dry creek beds can be designed and specified to compliment the aethetics of your landscape and add a new dimension to your site vistas.

Photo Credit: Sturgis Rock Solid Solutions

French drains are appropriate for controlling excessive moisture around foundations, where hardscapes and softscapes create pooling and where grade depressions create ponding in undesirable locations. French drains are basically just trenches filled with gravel. Sometimes drainage pipe is installed. French drains act as disguised dry creek beds, and can transport water under turf or other landscape features.

Including native wetland plants in high moisture areas can also control water excesses on site. Winterberry hollies, inkberry, florida anise, willows, red dogwoods, birches, cedars, horsetail, ornamental grasses, lillies, and rose mallow are all species native to Georgia which can withstand or even thrive in excessive moisture.

If the recent rains pointed out site drainage issues on your property, talk to a qualified landscape designer for advice about how to manage drainage, even harness excessive water on your property for asethetic or functional gain.