I planted columnar 'Spring Snow' crabapples (20-25' T x 15-20' W) on the east and west sides of the backyard to screen the view of the neighbors while leaving sunny beds where my flowers can grow. In addition to their oval crown, these trees have beautiful, sweet smelling white flowers in spring and no messy fruit. Unfortunately, here in Spokane we have a long season where these trees are leafless and don't provide much screening.
Although I love my eight 'Spring Snow' crabapple trees, my local nurseryman - whose nursery has been open as long as I've been alive, so he knows a lot - told me that these trees are falling out of favor with growers because they are susceptible to fire blight. This fungal disease can strike in spring and causes twigs and leaves to look as if they've been burned black. Infected trees should be sprayed immediately with a fire blight-rated pesticide, and infected parts should be pruned out, wrapped in plastic and put into the trash to avoid spreading more spores. I haven't had a problem with this, fingers crossed.
Recently my husband caught this photo of Santa laying eggs in our neighbor's yard. We endured this view for several weeks from our bedroom window before Santa left his eggs behind and went to rest for a few months. As my trees and our neighbors' trees grow, this scene will be blocked during the growing season, but I wish I had planted more tall evergreens to cover it year-round.
Two years ago, I talked my husband into pulling out some boxwood shrubs and planting two columnar Norway spruce trees (Picea abies 'Cupressina'). These columnar trees are said to reach thirty feet tall and five to six feet wide at maturity. Both are strategically planted to block views of the neighbors - especially their windows - when they reach full size.
The spruces have put on decent growth each year, and they'd surely grow more quickly in climates with a longer growing season. I can think of several spots where I'd like to plant more of them, but that would require removing other beautiful plants. It's so hard to balance functional evergreens with favorite beautiful plants.
This photo includes the young columnar spruces plus 'Green Tower' boxwoods (9' T x 2' W) and 'Fine Line' buckthorns (7' T x 2-3' W). I have ten of the GT boxwoods and seven of the FL buckthorns planted around the yard. Both shrubs are easy to prune to the height and width you desire, and they can be planted singly or in a row to create a hedge. Some types of buckthorn are invasive, but FL is not.
This GT boxwood in the front yard greets visitors as they come to the front yard. Kind of like a plant butler. I should call it Jeeves.
A 'Caesar's Brother' Siberian iris at center is columnar in spring and vase shaped later in the growing season. Many grasses have a lovely columnar form, like 'Karl Forster' feather reed grass, but I avoid ornamental grasses since they give me a rash and make me sneeze. To the right of the photo above, two of my 'Fine Line' buckthorns add height to the bed. This spring I decided they were too tall, and it was quick work to trim two feet of height off the top.
Last year I found room for a fifth dogwood - wish I had room for a dozen more - and planted this columnar 'Starlight' tree (Cornus kousa x nuttallii) at the corner of the dining room addition. It's reported to bloom heavily and grow vigorously to a height of thirty feet and width of twenty feet. Yes, it's obviously going to require pruning in this spot. Good thing I took a pruning class in college. Eventually it will give late afternoon and evening shade to the patio in midsummer.
At right is a columnar apple tree from White Flower Farm. I don't grow a lot of food, but I had the idea that a columnar apple would be fun. We'll see how it works out. Meanwhile, the upright shape is lovely.
If you live in a crowded suburban neighborhood like mine, screening views is important even if you don't have a large yard. Columnar plants - especially evergreens - are a good option for creating privacy without taking up too much room. Please learn from my mistake and plan for privacy so you don't have to look at your neighbors' junk or allow them to peer at you through second story windows. Let Santa lay his eggs in private.