Here’s where gardening with Rock Stars® can get really creative and fun! The only limit is your imagination.
We first saw examples of roof gardens during trips to Europe, where this seems to be a long tradition. Hen-and-chicks (Sempervivum) and various kinds of Stonecrop (Sedum) are often grown directly on top of terracotta or slate roof tiles where they cling by their tiny roots and take advantage of any little bits of soil or debris that gather at their base, supplying nutrients. Roof tiles are less common in most parts of North America, and we certainly don’t advise attempting to grow plants on top of asphalt or cedar shingles or other roof surfaces where standing moisture could cause problems over time.
However, garden sheds and other small structures – a dog house or play house – are the perfect opportunity to do some experimenting with rooftop gardening. Consider first laying down a thick rubber or vinyl barrier (the type used for water gardens should work, or other types from roofing supply stores) before installing the final roof surface. Relatively shallow-pitched roofs are a better choice than steep ones, where the plants might wash away in the first heavy rain storm.
Tiny little alpines will need some help adhering to the surface. We’ve seen a doghouse, for example, where the entire roof surface had a layer of soil a couple of inches thick, covered by sheet sphagnum moss then finally topped by a layer of chicken wire. It was a riot of colour from all kinds of succulents and other alpines. A roof garden planted as densely as this example requires regular watering.
On higher roofs, like on a shed, it might be possible to take the individual rosettes of a Hen-and-chick and actually glue them to the tiles using a hot glue gun. Another method is to make small soil pockets using pieces of dead sod (just ask your garden center if you can have a roll or two when they are discarding the old stuff). Flip the sod upside down, add a layer of sheet moss, then fix it down with a final layer of chicken wire and somehow attach this firmly to the tiles. Then you can poke in rosettes of Hen-and-chicks and little bits of Stonecrops, which will quickly root themselves into the soil below. Water these lightly every few days for a month or so, then just leave them alone and see what happens.
Our example of very simple rooftop gardens above is quite different from the serious, large-scale approach to creating a green roof. Many commercial buildings are now integrating green roofs into their design in cities all over North America. It’s a whole science involving a lot of high-tech materials, and not something that we could even begin to cover here. Building a green roof will require the help of professionals with experience. Try doing an internet search on key words such as green roof construction to locate information and experts such as Engineers who specialize in this area.
This is a fairly new technique for growing alpines, first started in Czechoslovakia. The result is very simple in construction and absolutely stunning to look at. Imagine large pieces of flat flagstone rocks standing vertically out of the ground, one next to the other with a gap of a few inches in between. This gap is filled with soil, then covered in gravel mulch and the alpines are planted in these long and narrow crevice spaces. The standing rocks could be gently curving, jagged and angular in shape or even neatly trimmed into rectangles or very geometric shapes. On a tight budget, even pieces of broken patio stones could be used to good effect.
For support, the lower portion of each stone is buried below the existing ground level before filling the gaps between the stones with the special alpine soil mixture. The result is a free standing rock structure that has a lot of great textural character and can easily be created for a large or a small space. You could even adapt this idea to containers and troughs, using flat pieces of thin slate, either natural or cut.
This information should get you off to a good start. For additional information including details on the topics below, download our more comprehensive PDF here.
- Rubble Gardens
- Gardening with Children
- Found Objects
- Boots & Hats
- Living Sculptures
- Decorating your Rock Stars®