Botanica Atlanta - Landscape Design, Construction & Maintenance

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.