Spending time in green spaces is good for all of us, better still when it’s your own private space where you can create your own little oasis of peace and privacy. If you live in a city where outdoor space is precious and have access to a flat roof, it makes sense to create a roof garden.
Start first with the practicalities:
Try to install some kind of shelter if the roof is very exposed, then you’ll be able to grow a wider range of plants. A solid barrier causes the wind to rush over the top and create turbulence, something like trellis is perfect because it filters the wind.
Check with a structural engineer that the roof is able to withstand the loading, plant pots can be very heavy, especially when wet. Use resin plant containers filled with a 50:50 mix of John Innes No 3 compost and multi-purpose compost ( you’ll need to tweak this mix depending on the type of plant); don’t forget to add a slow-release fertiliser to feed the plants.
Roof gardens are costly to make because of the time and effort taken to get everything up there. Think about the access and how easy it’ll be to get furniture, soil, plants and plant containers up there.
Roofs are usually very exposed and plants dry out quickly, so you’ll need easy access to water. Choose the type of plants that don’t need lots of watering, consider installing an automatic irrigation system if you have lots of plants.
Choose plants that will withstand these tough conditions, those grown by the coast or in hot Mediterranean climates fit the bill nicely.
These types of plants have various methods of managing in this environment.
For instance, plants with silver, felty leaves are covered in tiny hairs that protect them from drying out and the silver colour reflects the sun away from the plant.
Narrow leaves work well because they have a smaller surface area and loose moisture less quickly than large ones.
Avoid plants with large leaves such as Tracycarpus fortunei and banana plants. Their leaves become shredded in high winds; it’s a coping mechanism so that the plant has a functioning leaf, but it’s not very attractive.
Lavender: small evergreen shrub, with aromatic leaves & scented flowers (sun), they prefer poor, well-drained soil.
Sempervivum: low alpine alpine plants, happy in exposed, dry conditions. Add about 25% of horticultural grit to the compost so that the soil is really well-drained.
Pinus mugo ‘Mop’: a shapely, rounded dwarf conifer, has those narrow leaves so it’s very tough.
Cistus: evergreen shrubs in a range of sizes, may need winter protection if you have cold winters.
Trachelospermum jasminiodes: an evergreen climbing plant with white scented flowers and waxy leaves. Climbing plants are a good choice where space is limited.
Ornamental grasses such as Stipa tenuissima and Helictotrichon sempervirens look lovely and will move beautifully in the wind.
Herbs such as Rosemary and Thyme love these conditions and are happiest in poor, well-drained soil.
Many Vegetables grow well in containers, but will need protection from winds.
You may have to experiment a little to find exactly the right plants that suit your conditions, but it’ll be worth it.
Please leave a comment if you have a roof garden and let me know what works best for you.