Music and literature employ variation and rythym, allowing a piece to flow. How can these same principles be used in gardening? What are some ways that allow the viewer to move smoothly through a garden? Alternatively, what might you do to make the garden visitor come to a complete stop and pay attention to a particular plant or vignette?
Strong vertical elements— “exclamation point” plants— can serve either of these functions, depending on how they’re used. A pair of columnar plants flanking your front door or the entry to a path makes a statement: “Pass through here.” A tightly spaced row can serve as a hedge, especially if you’re constrained by a narrow space. Their minimal width will reduce the need for pruning, but it does necessitate buying more plants to get the job done.
If you don’t require a true hedge that totally blocks the view, place your plants more widely than usual. They may never fill in the gaps, but this “dotted line” still serves as a see-through picket fence, dividing one garden area from another. Another alternative, albeit an unconventional one: alternate two different but similar species in the line. I’ve heard this technique referred to as fenestration, i.e. a window effect.
If you want to add vertical interest to an otherwise flat-to-mounded perennial bed, plant a series of medium-height columnar plants at regular intervals. They’ll provide year-round structure, especially valuable in the winter when perennials die back, and won’t shade other plants to a significant extent. This repetition of an identical form will subtly move the eye through the bed.
Some clarification on terminology might be in order at this point. The terms columnar and fastigiate are often used interchangeably to describe narrow, upright plants, but there can be subtle differences between the two. Columnar plants have very short lateral branches; in the best varieties, the plant is a virtual column, essentially the same width from to top to bottom. Fastigiate trees and shrubs, on the other hand, have lateral branches that are almost vertical and grow close to the trunk. Although still narrow, the plant may be slightly egg-shaped. One source states that columnar plants tend to have a height/width ratio of approximately 5 to 1, while fastigiate ones may be closer to 10:1. Take these numbers with a grain of salt, and remember that both forms will get squattier with age. Neither are the same as a pyramidal plant, i.e. an inverted cone widest at the bottom. Think of your typical Christmas tree—and Happy Holidays, by the way.
Perhaps the most recognizable columnar tree is the iconic Italian (or Mediterranean) Cypress (Cupressus sempervirens) seen in so many paintings and photographs of the Mediterranean region and California. This Cypress would be a challenge to grow well in most of Virginia, however, not necessarily for the cold we get, but more for the summer humidity and the fungal diseases it can bring. Winter snow and ice can also wreak havoc, although there are some techniques to address that issue.
Many other conifers naturally grow tall and narrow but don’t qualify as truly columnar unless you choose a particular cultivar. Our ubiquitous red cedar (Juniperus virginiana) is available in the variety ‘Cupressi-folia’ (aka ‘Hillspire’), that should reach 12’-15’ in height and 4’-6’ in width. Its cousin, J. chinensis ‘Trautman’ will grow to about fifteen feet tall and four feet wide; foliage and cones are bluish green. The cultivar ‘Spartan’ is somewhat narrower, 20’ by 4’.
Among columnar broadleaf evergreens, Ilex crenata ‘Farrowone’ (typically sold as ‘Sky Pencil’) is one of the more popular. (See photo.) A typical 4’-6’ specimen will only be about a foot wide. Don’t confuse this with the variety ‘Sky Pointer’, a wider pyramidal form with a looser, more natural habit.
The ever-popular boxwood does not have to be a well-sculpted meatball. Among the columnar choices, ‘Graham Blandy’ (named for the original benefactor of U.Va.’s Blandy Experimental Farm) will reach 9 feet in height, 18 inches in width. ‘Pyramidalis’ is similar at 10’ to 12’ by 3 feet. ‘Dee Runk’ (named after B.F.D. Runk, onetime Dean of the University) typically grows to 5 feet tall and one foot wide, but may eventually become larger.
Deciduous trees provide additional choices among columnar varieties, especially if you’re looking for a larger plant. The fastigiate sweetgum, Liquidambar styraciflua ‘Slender Silhouette,’ can grow to forty feet or more, but should stay at a width of six feet. A couple of oak varieties can also provide the tall-and-slender look. For the glossy, fine foliage of a pin oak, look for Quercus palustris ‘Green Pillar’, also sold as ‘Emerald Pillar’ or ‘Pringreen’. In the white oak group, the hybrid Quercus x warei ‘Nadler’ (sold under the name ‘Kindred Spirit’) will reach 35’ by 6’ after 30 years. If you’re fond of Ginkgoes, at least two narrower forms are on the market: ‘Princeton Sentry’ will grow to 60’, but at 25’ wide would not be considered truly columnar; reportedly smaller and narrower, Ginkgo biloba ‘Blagon’ is trademarked as ‘Goldspire.’ Both varieties are reportedly males, so no stinky fruits.
Caring for Columnar Plants
Snow and ice may damage any plant, but they can easily turn columnar plants into botanical incarnations of Thing 1 and Thing 2. Loosely crisscrossing shrubs with natural-fiber twine or pruned vines can keep them upright when winter precipitation falls. (Unless you’re more comfortable on a ladder than I am, this isn’t going to be practical when they get taller.) I’ve also read that shearing plants tightly will discourage snow from sticking to the foliage. Sounds like this could indeed work for the white stuff, but I’m not sure it would do much good when you’re dealing with ice from freezing rain.
Although these horticultural exclamation points add drama to a landscape, allow me to throw out one caveat: don’t plunk one down in the middle of your front lawn like a sore thumb. It might provide more drama than you—or your neighbors—are looking for.