Hello, I have a couple of oddly-shaped containers -- only about 8" x 8" footprint, but over 2 feet tall -- and would like advice on year-round plants that would work in these pots. I'm in Vancouver, with a northwest-facing balcony. Evergreens would be ideal, but any year-round outdoor plant, preferably one that grows tall, would be fine. They obviously need to be something that will grow up rather than out, and can grow deep roots rather than spreading wide. Thanks!