The garden committee at a condo complex is wanting to find a tree for a spot about 6′(east/west) by 12′ (north/south) situated in a ravine. There is good morning and some afternoon light. There are a couple of shade trees – an ash and and a smaller tree on the east side. There is adequate water from irrigation. It is a confined spot between an asphalt path and the rising side of the ravine. I am unsure of the soil conditions, probably clay at deeper levels, but it can be amended. We had a Redbud there for 3 years (Forest Pansy variety). It did well until it died with the ice storm. We would be grateful for any thoughts or suggestions you might have.
There were so many victims of last year’s ice storm, and I am sorry your Forest Pansy Redbud was amongst them: Cersis canadensis is more vulnerable to extreme weather than the species suggested here as replacements.
Specimen trees can be spectacular in different ways, from their spring blooms, to a distinctive shape, interesting bark, fall colour or the branching habit revealed in winter. For beautiful spring bloom (although some would say nothing could rival the Eastern redbud in this department!) you could consider a pagoda dogwood, Cornus alternifolia, with its lovely white flowers in spring, its very distinctive horizontal branching habit, and its fall foliage of red-purple. The serviceberry (in its single-stemmed form, rather than the multi-stemmed), Amelanchier canadensis, likewise has a beautiful spring floral display, followed by small blue-black fruit in summer and fall foliage that is truly showstopping. For a tall, narrow alternative in your space, you might consider an upright Siberian crabapple, Malus baccata ‘Columnaris’ or one of the ornamental Chanticleer pears. Two gorgeous options, both with exfoliating bark, are the paperbark maple, Acer griseum or the river birch, Betula nigra. The paperbark maple is a great choice for a small space that is not in full sun, where its copper/cinnamon bark can be appreciated. The exfoliating bark of the river birch is in shades of brown and pink; the “river” in its name implies that it does not mind being close to moist areas, particularly in the springtime. A final thought is the stunning Ginkgo biloba, perhaps one of the narrower cultivars like ‘Princeton Sentry’. This is a tree that does very well in an urban environment, resistant to pests, diseases and pollution alike. Its best features are its beautiful fan-shaped leaves, its shapely form and its golden fall foliage.
When you have chosen your tree and are ready to put it into the ground, you may be interested in this comprehensive guide to planting offered by the Toronto Master Gardeners: http://www.torontomastergardeners.ca/index.php/factsheet/planting-a-tree-a-toronto-master-gardeners-guide/ . Here is an excerpt from this guide in regard to soil amendment:
You should not add new bags of soil or soil amendments when planting a tree. Ideally, you have well-drained, organically rich soil or soil perfectly suited to your chosen tree that will enable the new tree to set down roots and thrive. More realistically, you have wisely chosen a tree that will tolerate and thrive in your soil conditions. It may seem nurturing to add new top soil, manure, compost or peat moss to enhance the soil, but in fact, you are creating a soil pocket which is unlike the surrounding soil. The roots may initially grow well, but, as they come to the edge of the soil in the planting pocket, they will resist growing beyond into the surrounding soil. The tree will be stronger and grow faster if its roots are able to adapt quickly to the given soil conditions and begin to grow out and down into the earth beyond the prepared hole.
If you would like to improve the soil, do so gradually by using organic amendments, such as a layer of disease free leaves, in the form of a mulch. Spread mulch around the surface of the soil after the tree is planted, so it will slowly and naturally decompose and work its way into the soil.
Very best of luck with your new tree!