Crimes Against Horticulture Update: Bolder Boulder Use

If you are a frequent skimmer of this blog, you know I like to occasionally like to highlight things I call Crimes Against Horticulture (CAH-there are even social media accounts dedicated to this!): murderous horticultural practices or terrible landscaping ideas. The topic of this CAH alert: the use of boulders in the midwestern landscape.

This post has been a long time coming – I’ve remained silent as long as I could stand it, and then the other day, I witnessed yet one more “strange” (or at least, not how I would use them) use of large boulders in someone’s yard. Here in Michiana, a lot of our boulders come from farm fields. The farmer wisely removes them so as to not destroy expensive equipment. Someone sees the large product of ancient geological processes and says to themselves, “Hey, I like that rock. I’ll get someone with heavy equipment to place it prominently in my front yard. Then, I’ll make a flower bed around this geological wonder and fill it with petunias.” Or, they decide to place them in a nice line, without much conceptual tie in with the rest of the yard. This boulder placement is similar to the miniature “well” made out of wood or lone peony out in the turf with no connection to anything else. The well, peony or boulder themselves are not so much the issue as is how they are used. Many homeowners place a random smattering of objects and plants around the property, and it looks disjointed. Incorporating the simple design technique of drawing a bed line around these objects and connecting them together creates some visual harmony.

Now, dear reader, I would not leave you with only a scathing treatment of landscaping faux pas, but instead, I will share some “enlightened” positive options that will make you the next hip, non-hipster gardener in town. To get an opinion other than my own upon the subject, I asked someone who spoke on the condition of anonymity (and my source is real, I promise) from deep within the landscaper community for five tips to make your boulders bolder. This is their list:

Make the stone look natural This is the most important point and in some ways the rest of these tips are the “how” in making the boulder “feel” natural. One of many things I have learned from the Japanese (masters of stone in the garden) is to observe how stone in part of the country looks out in nature (this is especially true if you are using rocks sourced from your region). In our case, fairly rounded glacial stone (often granite) is the norm. This is due to glaciers majorly influencing the large shape of the land in this part of the Great Lakes. Glaciers scraped rock off the face of Canadian mountains like an ice cream scoop and dumped their thirty-one flavors throughout the Great Lake states. Observe grade elevations and stones left in a terminal moraine, for example.

Make sure the rock is buried and not sitting on top A glacier does not normally place a boulder neatly on top of the soil, fully or mostly exposed, but rather partially or mostly buried. This will look more natural and “soothing” to the eye. There is an easy way to determine how deep to bury each stone. Look for the widest portion of the stone, the longest two points, and this becomes your soil line when the earth is compacted/settled around it. The Japanese look for a stone’s tenba, which helps determine the rock’s top and bottom.

Group stones in odd numbers Odd groupings of landscape elements is a good guideline for creating natural looking landscapes, but this is not always the case. My Japanese garden sense used to say, “birds don’t poop in threes”, referring to the tendency in western landscape design to always make odd numbered arrangements. It is okay to add some even numbered stuff as well. It is more important to create arrangements that are asymmetrically balanced. Nature produces such arrangements more often than not.

Everything should flow together and compliment each other If you are placing more than one stone in the landscape, make them relate to each other and visually connect, usually literally. Make the stones “kiss”. This is done a lot like fitting a puzzle together. The negative space in one stone is neatly fitted with the positive space of another, touching the two stones together. A number of years ago, when I had not reached rock nirvana, I had arranged three stones in a triangle together in a flower bed with mulch between each. It always bothered me until I learned to pull the stones together. The placement of the first stone in the arrangement will determine the placement of the next and so forth until you meet your goal. 

Stone uniformity (do’s and don’ts of selection) I have seen some dry stacked boulder walls where the landscaper used stones of almost uniform size and shape. This not only looks less appealing, in my opinion, but they are less stable too. Create boulder arrangements with varying sized stones and shape. Where you want uniformity is in the type of stone used. I would not recommend mixing stones from different geological formations (i.e. glacial granite with sandstone or sedimentary shale) or widely different mineral content. Use similarly colored and shaped stones together just like you would find in a natural formation. You should use angular rock with angular rock, for example. 

Now that you have been greatly enlightened, go forth and be bolder with boulders!

Josh Steffen, Horticulture and Facilities Manager

Missed any of Josh’s recent posts? Click below to read more:

1. Navigating through the Prairie with the Compass Plant: August’s Native of the Month

2. Combatting Purple Loosestrife

3. Garden Phlox (Phlox paniculata): July’s Native Plant

4. The Invasive Tree-of-Heaven

5. Nothing False about this Native!

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