Finding a small tree for an urban garden

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Q: I’m looking for a small upright tree (maximum 20-25’h) for a southwest-facing spot in my small urban garden. I’d like a fast-growing tree. What do you think of ‘Ruby Lace’ gleditsia or Cercis canadensis ‘Forest Pansy’? How about Japanese tree lilac ‘Ivory Silk’? Is there a specific Japanese maple you would recommend?

This is a question I’ve heard many times in my years in horticulture, but it has no easy solution.

Fast-growing trees just don’t stop at 25 feet, they rocket on upwards. Cercis canadensis ‘Forest Pansy’ is a lovely tree, but it does much better in a climate where it gets enough summer heat to ripen the wood. In coastal B.C. it might not get enough heat, which results in dieback during winter. You’ll often see them with dead branch tips.

Gleditsia triacanthos ‘Ruby Lace’ is a handsome tree – in someone else’s yard (or even someone else’s province!). We had many gnarled specimens of this at VanDusen Botanical Garden, set in the Great Lawn and along the Rhododendron Walk. But the gardeners constantly struggled with suckers that came up beneath the trees. Also, this species has invasive tendencies. You can see it growing along the freeway in Oregon. It’s also subject to a variety of pests and diseases.

Ultimately it will reach at least 60 feet, so I don’t think you would be happy with that one.

I haven’t had as much personal experience with the lilac, but ‘Ivory Silk’ is more shrub-like in habit.

So, what would I choose for a small tree? I love my Cornus kousa for its vase-shaped habit (which means I can garden beneath it) and year-round good looks. Our native vine maple (Acer circinatum) is a lovely small, multi-stemmed tree. The cornelian cherry (Cornus mas) has yellow flower in late winter and edible (for cooking) red fruits. Some of the magnolias (‘Elizabeth’ and ‘Galaxy’ for example) stay relatively small. Disease-resistant flowering crabapples (‘Adirondack’, ‘Jewelcole’, ‘Strawberry Parfait’, ‘Golden Raindrops’) are pretty and also have edible (for cooking) fruit. Be absolutely sure to buy a disease-resistant cultivar, however. The various species of Nyssa and Stewartia are all handsome and well behaved.

In terms of Japanese maples, there a many wonderful cultivars. Among the well known, available upright cultivars are ‘Katsura’, ‘Osakazuki’, ‘Shindeshojo’ and ‘Bloodgood’. Check out your favorite garden center in spring when the selection is best, make a list of the ones that catch your eye, and then spend a little time reading up on them. The classic maple book is Japanese Maples by J.D. Vertrees, recently updated with author Peter Gregory. The new book is luscious, but the old version was also excellent and is available used at a reasonable price. Also excellent is Maples for Gardens by the VanGelderens. Just be warned: maples can be habit forming. Some of my best friends are addicted to them!