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Mark and Ben Cullen’s tips for vertical gardening

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Mark and Ben Cullen’s tips for vertical gardening

Vertical gardens are having a moment. Here are top tips to consider when looking at installing raised beds or green walls.



Build at least a foot tall

This will ensure whatever grass or potential weeds you are building atop are adequately smothered and get the minimum functional benefit of a raised bed. However, you can go as high as you like as long as you are prepared to backfill. If accessibility is your goal, you can build it right up to waist height and backfill with a mix of gravel and topsoil to ensure draining, with a top layer of triple mix. You will want the top 12 to 18 in. of soil at minimum to be a good quality triple mix, rich in compost.

Consider spacing and patterns

To maximize the usability of your raised beds, make sure they are accessible from all sides and that a wheelbarrow can pass through easily. If you decide to use turf pathways, ensure that your lawnmower can manoeuvre. Using patterns can be visually pleasing, especially when arranged geometrically, but we recommend that you keep your beds roughly equal-sized if you intend to plant vegetables. The reason is that having equal-sized beds can help with planning year over year as you work through your crop rotations; for example, you wouldn’t have to limit your tomato harvest one year because they are being rotated into a smaller bed.

Use durable materials

Cedar or redwood are your most naturally rot-resistant materials. In western Canada, red cedar is famous and is exported around the world for these qualities. Many folks don’t realize that locally available white cedar is also well suited for the job in eastern Canada. You can dress up wooden raised beds with capped corner posts or whatever wood finish works within your broader design scheme. Brick raised beds can add a formal look to any garden, regardless of what you decide to grow in them, and stone works well for cottage gardens. The added benefit of stone is that when constructed using dry masonry, the crevices provide habitat for garden critters, which helps build biodiversity.


We specify “living” walls because there are non-living, preserved green walls that can provide a look but do not necessarily fall within our gardening domain. Here is what you should consider for a living green wall:


Wall selection

South-, east- and west-facing walls will obviously work best, depending on the light requirements of what you intend to grow. For interior walls, skylights and proximity to windows will be key. Anything further than 10 ft. from a window, the natural light penetration drops off dramatically.

Wall protection

Whether for interior or exterior walls, keeping moisture away from building architecture is crucial. Occasionally, we see purpose-built exterior living walls which can be built from the ground up to accommodate the moisture that accompanies plants, where creative freedoms and costs are less restricted. Interior mold and exterior rot can be unfortunate consequences of a mismanaged green wall, so take great care to protect your wall using an impermeable plastic membrane, such as an exterior basement waterproofing membrane.


The DIY-route

If you are looking for a project, you can take many different avenues. Simple cedar frames can be constructed and fastened to a wall to suspend smaller containers of potting soil arranged in a series, where you would treat it as a cluster of indoor plants that are watered from a watering can like any other indoor plants. Since we’re strictly amateur carpenters (only in the non-gardening season), we will refrain from advising you any further than this.

The professional route

This is where you will get maximum impact without having to worry about a potential water problem spreading into other areas of your home. A growing number of outfits specialize in modular systems that fully integrate growing medium, irrigation, drainage, and plant material into one cohesive system. Prices vary but expect to pay in the neighbourhood of $100 per sq. ft., depending on the sophistication. Look up a “green wall installation” in your city, and you will easily find professionals who can consult based on your specific needs.


The most sophisticated living walls will be mostly maintenance free – yes, they are even self-watering. A rudimentary system will require that you monitor as you would any other indoor or outdoor plants and water accordingly. Keep an eye out for common houseplant pests such as aphids or gnats, and treat accordingly.


Mark Cullen is a Member of the Order of Canada. He reaches more than two million Canadians with his gardening/environment messages every week. Ben Cullen is a professional gardener with a keen interest in food gardening and the environment. You can follow both Mark and Ben on Twitter (@MarkCullen4), Facebook (facebook.com/MarkCullenGardening) and Instagram (instagram.com/markcullengardening). Receive their free monthly newsletter at markcullen.com.


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