My church is considering planting a Japanese Maple in an internal courtyard as part of their 50th anniversary. While Japanese Maple are quite pretty, I was concerned that it was an invasive species (https://www.invasiveplantatlas.org/subject.html?sub=3001). I’ve also found this site that talks about how to care for it and what can go wrong (https://www.gardeningknowhow.com/ornamental/trees/japanese-maple/japanese-maple-tree-lifespan.htm).
The church is in central Mississauga. The proposal is to plant it in one of the internal courtyards shown below.
The roof of these courtyards is about 9′ at the eaves and 12′ at the peak. I’ve been told that the Japanese Maple was chosen for it’s ability to withstand the hot temperatures expected in that location. My research suggests that a Japanese Maple prefers partial shade that it may not find in this location.
Is there an indigenous tree that would be appropriate for this location?
If they put a Japanese Maple there, are they going to get the 50+ years life they are looking for?
My personal preference would be an Oak of some kind but I can’t imaging an oak fitting in that location for very long.
If you had any suggestions, I would appreciate it.
First of all, Japanese Maples, Acer palmatum, is not considered invasive in Ontario, or anywhere else in Canada.
From your description I assume the following regarding the church courtyard: that it is 12’ at the apex and fully enclosed (therefore relies entirely on artificial irrigation), receives full sun (i.e. over 6 hours of direct sunlight every day), and that there is no mechanism to regulate the temperature and humidity within. Such a space can become unbearably hot, especially if it receives late afternoon sun from the southwest. Japanese maples originate from cool montane regions in east Asia and may become stressed by the heat. This can be mitigated by using soil that is acidic and high in organic matter; watering consistently and deeply; and keeping the soil cool (e.g. mulching). Give the tree as much room as possible underground, where its roots can expand properly. Longevity of a tree cultivated in an artificial environment is notoriously unpredictable. If your church wants a Japanese maple, choose a cultivar that is more tolerant of heat stress.
The courtyard environment is challenging for any tree, not least due to its severe height limitation. 12 feet is not enough for a tree unless you cultivate it like a large bonsai. Or, you can plant a small tree and keep it severely pruned to maintain height. Neither is ideal. Throw in potential of heat stress and a desire for longevity, and the short list of suitable trees quickly dwindles. Why? Because trees that love sun and live long are generally forest canopy trees that seek to tower over everything else, while smaller trees are usually understory and survive under deciduous shade. Understory trees prefer cool, moist, acidic, organic soil. The only heat-loving native small trees that I can think of are from the genus Rhus (sumac), which are relatively short-lived (20-30 years).
The following is a list of small trees that grows in full sun, have enough ornamental qualities to be a specimen tree, and have a potential lifespan of 50+ years; Smaller specimens are 15 feet tall; none of them are truly heat-loving so it is important to keep them well-watered (*denotes native to Ontario):
- Amelanchier canadensis* downy Serviceberry
- Cornus kousa kousa dogwood
- Magnolia x soulangeana saucer magnolia
- Malus sargentii Sargent’s crabapple
Alternatively, consider a slow-growing dwarf conifer, which has the advantage of evergreen foliage, strong form, and low maintenance.
We wish your church the best of luck with the anniversary courtyard tree.