Your zone is not the number you remember
Check the current plant-hardiness information for your address using Canada’s Plant Hardiness site. Discuss exposure, snow cover and the conditions in each bed with the nursery or designer; one city-wide zone number does not describe every planting location.
That makes a zone number remembered from a nursery tag ten years ago an unreliable guide. Check your own address on Canada's Plant Hardiness site, because the zone boundary can fall between one part of the city and another.
Containers and raised beds need a planting approach suited to their exposure and winter conditions. Ask the nursery which plants and protection methods fit the actual bed rather than applying a universal zone adjustment.
Map salt exposure
Map the places where de-icing salt and cleared snow reach your beds. Exposure varies with how paths and driveways are maintained; ask which plants tolerate the conditions on your property.
The plants that fail there are the ones most often planted there. Eastern white cedar hedging along a driveway, boxwood along a front walk, and most broadleaf evergreens brown out on the exposed side and do not recover, because the damaged tissue is the previous year's growth.
Let actual salt and snow-storage patterns shape the planting list. Discuss tolerant species, setbacks and alternative bed locations with the designer rather than relying on a universal distance.
Snow is protection and snow is a load
Consistent snow cover insulates crowns and roots, and a mild, snowless January with hard frost is considerably harder on perennials than a cold one under half a metre of snow. That is why the same plant survives in a back garden and dies in an exposed front bed on the same lot.
Snow is also weight and it is placed. Where is the plough pile going, where is the roof shedding, where does the shovelled path get emptied. A shrub under the driveway pile until mid-April emerges flattened, and an upright evergreen under a roof shed breaks open in the middle. Both are design decisions rather than plant failures.
Frost heave is the third winter mechanism. Repeated freezing and thawing lifts newly planted perennials out of the ground in their first winter. Plant early enough in autumn for roots to take hold, mulch after the ground has frozen rather than before, and check in April for anything that has been pushed up, pressing it back in rather than leaving the roots exposed.
Soil is where the budget should go
A large part of Ottawa sits on Champlain Sea clay, which swells when wet, shrinks as it dries and drains slowly. On a suburban lot the topsoil above it is often 100 mm of builder-grade material over compacted subfill, which is not a growing medium.
Have the soil, drainage and proposed plants assessed before choosing a bed depth or soil amendment. Ask for a site-specific preparation plan, including how the planting area will drain and how existing roots will be protected.
Request establishment-care instructions for the actual plants and soil. Watering frequency should respond to rainfall, drainage, plant needs and seasonal restrictions rather than a fixed calendar applied to every garden.
Deer, rabbits and where they are
Browsing pressure is a geography question in this city. Kanata, Stittsville, Manotick, Greely and the properties backing onto the Greenbelt or farmland see real deer and rabbit damage through winter, when other food is under snow. Inner-city neighbourhoods largely do not.
The plants eaten first are also the ones most commonly planted: cedar, yew, tulips, hostas and young fruit trees. A planting list that works in the Glebe can be stripped by March on a Stittsville lot backing onto a field.
Discuss browsing protection with the nursery or designer, including species choice, guards and physical barriers where appropriate. Ask about maintenance and follow any product instructions rather than assuming one protection method works on every property.