SOME PARAGRAPHS NEED PUNCTUATION, and my garden’s like that–in need of the occasional exclamation point, specifically. So for the first time in 30ish years of gardening, I’ve gone and done it: adopted an evergreen “!” to help me state the case. My choice was a columnar American arborvitae, Thuja occidentalis ‘Degroot’s Spire,’ but there are others (especially if you garden in a slightly warmer zone than my 5B). That’s it doing improvised temporary duty in a pot, above, while I figure out where it will really go. More on the topic of vertical accents, in print or podcast:
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THE MAY 7, 2012 EDITION of the weekly podcast I do with the nation’s smallest NPR affiliate, Robin Hood Radio in Sharon, Connecticut (WHDD), was on the topic of vertical accents in the garden, particularly evergreen ones. Stream it now, or subscribe free on iTunes or the Stitcher app. Enjoy!
This first-ever columnar conifer in my garden career came about quite by accident. I was actually looking for what a friend refers to as “a blob” (a sort of lumpy, wider-than-tall, hummocky-shaped shrub) to replace a Daphne ‘Carol Mackie’ that was badly snow-damaged last fall.
Shop as I might for the right new “blob,” I saw nothing that was just right. And then I bumped into another friend at the garden center, who said, “Why not something vertical instead? Change it up.” Aha!
Punctuation Points I Considered:
- Thuja occidentalis ‘Degroot’s Spire:’ A columnar form of American arborvitae with twisted, almost spiraling foliage that gets to 10-20 feet and 3 to 5 wide, depending who you believe and how you prune. Zones 2-7. Sun to part shade.
- Ilex crenata ‘Sky Pencil’ (Japanese holly): Grows to 10 feet and 2-3 feet wide; will need help, such as from a cat’s cradle of fishing line, to prevent splaying open when it’s tall. Zones 5-8 or 9, though I worried this wouldn’t be hardy enough for me; some references disagree on the zone. Full sun best but adapts to part shade. The Monrovia Nursery profile.
- Buxus sempervirens ‘Graham Blandy:’ A columnar boxwood reaching 6 feet or more (maybe 15 after many years) but under 3 feet wide. Zones 5 or 6-8. Full to part sun. Weston Nurseries also has a good profile of this one. I’m also interested in learning more about the newer cultivar ‘ Monrue,’ a.k.a. ‘Green Tower,’ 9 feet tall and under 2 wide.
- Cephalotaxus harringtoniana ‘Fastigiata:’ This plum yew is much less tight and narrow, especially as it gets older, than the others, at 10 feet tall and 6 feet wide with a vase-shape. It’s also not suited to heavy snowload country (she says, having maimed it herself); Zones 6-9. But if you want something with a linear leaf (yew-like foliage) and can accommodate the width…. Part sun.
SUCH COLUMNAR SUBJECTS would also be useful grouped for hedging, of course. A note when grown in pots as a specimen: If you leave a big weatherproof pot out in winter, the plant’s roots will have less insulation that in the ground (meaning they’ll be less hardy). Select something about two zones hardier than your actual zone for such exposed usage. Or plan to put them in an insulated shed or garage for the winter, which will cheat you a half-zone or a zone, in my experience. Here in Zone 5B I can overwinter a potted Zone 6A or maybe a 6B plant in my garage, but I wouldn’t count on even a 5B plant liking life out in the elements in a pot–a Zone 3 plant will make it, and a Zone 4 one might. Experiment, since each winter weather, plant, pot size and shelter makes for a different combination.