Plants for Roof Top Garden Between Patio Stones

by Michael Faulkner
(Ottawa)

We have a series of patios constructed of patio stones, positioned around a large area (roof top terrace)of crushed rock. These areas include a sitting area with couches/chairs (west side), a dining area (west side), a breakfast nook (east side) and a sunning area (north side).

in all cases, patio stones are laid on a 4" deep bed of crushed rock, with spacing between patio stones to allow for planting of thyme, sedum, etc between patio stones.

This arrangement allows for plantings that require no more than 4 inches of dirt (getting to roof surface) and plantings that will not extend roots/shoots aggressively (roof is concrete with insulation, heavy vapour barrier and then crushed stone).

The terrace is 1,000+ sq ft; the planting areas occupy 300 square feet. The terrace receives full sun and significant wind.

In Ottawa, summer temperatures will approach 32 degrees Centigrade; winter temperatures approach -20 Degrees Centigrade.

What would be your recommendations for plant material between patio stones in these circumstances?

ANSWER
I depends on the layout of the space. Sometimes taller ones can be used and other times lower ones. Personally, I have found Sedums hardier than Thyme. And there are so many kinds! I would love to see them planted in small groups of one kind next to other groups with a different texture and perhaps color. To make a tapestry affect.

So I can't really advise on specific varieties and for it to look good, it would have to be designed in an interesting layout.

However, just to name a few...Turkish Delight, Cauticola and Dragons Blood are good ones. Dragons Blood has a reddish cast (not bright at all) and Cauticola is one of my favorites as it is a very soft blue-gray color. And pictured above is a pink Sedum...I'd have to get the name for you.

As you probably know, Sedums take dry conditions.

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