Download the Region of Halton Native Plant List.
Conservation Halton’s Landscaping and Tree Preservation Guidelines lists native species suitable for our region in Appendix 1.
The Society of Ecological Restoration (Ontario Chapter) has a number of useful resources on their site including a list of native plant suppliers.

Trees:
Red Maple (Acer rubrum) – moist to wet, part shade conditions
Freemans Maple (Acer freemanii) – moist to wet, full sun to part shade conditions
Silver Maple (Acer saccharinum) – moist to wet, full sun to part shade conditions
Sugar Maple (Acer saccharum) – normal / moist, shade conditions
Yellow Birch (Betula alleghaniensis) – rich moist soils, full sun to full shade.
White Birch (Betula papyrifera) – well drained soils, full sun to part shade.
Blue-Beech or Ironwood (Carpinus caroliniana) – moist soil conditions, in shade (understory beneath broadleaf trees)
Bitternut Hickory (Carya cordiformis) – moist to wet soils, part shade
Shagbark Hickory (Carya ovata) – dry to wet soils, thrives on heavy clay, full sun to part shade
Hackberry – (Celtis occidentalis) – moist sites, sun to part shade
Witch-Hazel (Hamamelis virginiana) – moist shaded sites as understory.
American Hazel (Corylus americana) – dryer soils, full sun to part shade.
American Beech (Fagus grandifolia) Moist, well-drained soil, part to full shade
* White Ash (Fraxinus americana) – normal / moist, sunny conditions
* Green Ash (Fraxinus pennsylvanica) – moist / wet, shade conditions
Eastern Red Cedar – (Juniperus virginiana)
Hop hornbeam or Ironwood – (Ostrya virginiana) – well drained soils, part to full shade
White Spruce (Picea glauca) – normal / moist – part shade conditions
Eastern White Pine (Pinus strobus) – normal /moist, sunny conditions
Black Cherry (Prunus serotina) – dry to moist conditions, sun to part shade.
Tulip Tree (Liriodendron tulipifera) – normal / moist – part shade conditions
White Oak (Quercus alba) – all conditions
Swamp White Oak (Quercus bicolor) – Wet soils, full sun to part shade.
Bur Oak (Quercus macrocarpa) – moist to wet, sunny conditions
Chinquapin Oak (Quercus muehlenbergii) – Dry soil, rocky areas (especially limestone) full sun to part shade.
Pin Oak (Quercus palustris) – moist to wet, sunny conditions
Red Oak (Quercus rubra) – dry sunny conditions
Shumard Oak (Quercus shumardii) – moist to wet soils, part shade.
Black Oak (Quercus velutina) – dry or well drained soils (eg. steep slopes), full sun to part shade
Sycamore (Platanus occidentalis) –moist to wet soils, sunny / partial shade
Eastern Cotton Wood (Populus deltoides) – moist to wet, sunny conditions
Largetooth Aspen (Populus grandidentata) – moist fertile conditions, full sun to part shade
Trembling Aspen (Populus tremuloides) – all conditions
Eastern White Cedar (Thuja occidentalis) – all conditions
Basswood (Tilia americana) – Moist soil conditions, part sun to full shade.
Eastern Hemlock (Tsuga canadensis) – moist shady conditions, especially north facing slopes
American Elm, or White Elm (Ulmus americana) – Moist to wet conditions, full sun to part shade
* Ash species are not recommended for planting because of their susceptibility to the Emerald Ash Borer.
Shrubs:

Red Osier Dogwood (Cornus stolonifera) – moist to wet, sunny conditions
Highbush Cranberry (Viburnum trilobum) – moist to wet, sunny conditions
Nannyberry (Viburnum lentago) – moist to wet, part shade conditions
Hawthorn (Crataegus spp.) – normal to moist, sunny conditions
Grey Dogwood (Cornus racemosa) – all conditions
Ninebark (Physocarpus opulifolius) – all conditions
Silky Dogwood (Cornus amomum) – part shade, moist (says it likes sand)
Buttonbush (Cephalanthus occidentalis) – part shade, wet
Common Elderberry (Sambucus canadensis) – full sun, wet
Red Elderberry (Sambucus pubens) – shade, moist
Purple Flowering Raspberry (Rubus odoratus) – shade, moist
Meadowsweet (Spirea alba) – full sun, moist
Spicebush (Lindera benzoin) – shade, moist
Witchhazel (Hamamelis virginiana) – full sun, dry
Pussy Willow (Salix discolor) – full sun, wet
Bebb’s Willow (Salix bebbiana) – full sun, wet
Choke cherry (Prunus virginiana) – full sun, dry
Downy Arrowood (Viburnum rafinesquianum) – full sun, moist
Smooth Serviceberry (Amelanchier laevis) – part shade, moist
New Jersey Tea (Ceanothus americanus) – full sun, dry
Maple-leaved viburnum (Viburnum acerifolium) – shade, moist