Mulch is one of the simplest upgrades you can make to a garden bed, but not all mulch performs the same way in Ottawa's climate. Cold winters, warm summers, and the occasional heavy spring rain all affect how different materials hold up. The right choice depends on what you're mulching, how long you want it to last, and whether you prefer a natural look or something more permanent.
Cedar mulch: the Ottawa standard
Cedar mulch is the most widely used mulch in Ottawa gardens, and for good reason. The natural oils in cedarwood slow decomposition, so a cedar application typically lasts two full seasons before it needs refreshing. The same oils also provide mild insect repellent properties, which helps around foundations and garden beds adjacent to the house.
Cedar mulch is available in red-dyed and natural brown. The red colour fades within the first season, but the natural brown holds up better over time. Apply at a depth of five to seven centimetres (two to three inches) for best weed suppression.
Hardwood mulch: dense and long-lasting
Hardwood mulch is heavier and more compact than cedar. It breaks down faster, which means it feeds the soil more actively, but it also needs replacing annually. Hardwood is a good choice for slopes and areas where lighter mulch might wash away during spring thaw or heavy rain.
The dark, uniform colour of hardwood mulch gives beds a tidy, finished look. It's also slightly cheaper per cubic metre than cedar, making it practical for large properties.
Rubber mulch: permanent but hot
Rubber mulch made from recycled tires never decomposes, so you install it once and it stays. The downside is that rubber absorbs and retains heat, which can stress plants in full-sun locations during Ottawa's hot Julys. It's better suited to playgrounds, dog runs, and decorative areas without sensitive plantings.
Rubber mulch doesn't provide any soil benefit, unlike organic mulches that break down and improve the soil over time.
Stone mulch: river rock and decorative gravel
Stone mulch, including river rock and decorative gravel, is permanent and provides excellent drainage control. It's ideal for areas around foundations, under downspouts, along driveways, and in low spots where water collects. Stone doesn't break down, so it never needs replacing, and it provides a clean, modern finish.
The trade-off is that stone doesn't improve the soil. For garden beds with perennials and shrubs that benefit from organic matter, organic mulch is a better choice. Stone works best as a complement to organic mulch, not a replacement.
How much mulch does an Ottawa garden need?
A standard application is five to seven centimetres (two to three inches) deep. That works out to roughly 0.03 cubic metres per square metre of bed area. For a typical 10-square-metre garden bed, you need about 0.3 cubic metres of mulch.
Piling mulch too deep -- more than 10 centimetres -- traps moisture against the stems and roots of plants and can cause rot. Keep mulch pulled back a few centimetres from the base of shrubs and tree trunks.
When to mulch in Ottawa
The best time to mulch in Ottawa is late May through early June, after the soil has warmed up and spring rains have settled. Mulching too early in spring keeps the soil cold and slows plant growth. A second light top-up in mid-summer keeps beds looking fresh through August.
Fall mulching is optional. A light application before winter insulates perennial roots, but heavy fall mulch can harbour voles and mice through the winter months.
Our mulch installation service
Adel's Yard Services handles mulch delivery and installation across Ottawa and surrounding areas. We prep beds by clearing old mulch and debris, then install fresh mulch at the correct depth with clean edges along walkways and driveways. Learn more about mulch installation or get a free quote with your bed dimensions.