Living

10 plants for roof greening

Sira Huwiler-Flamm

Green roofs not only represent real eye-catchers in residential areas – they also provide extra insulation, extend the life of the roof and become habitats for bees, insects and birds. However, for an easy-care green roof, there are a few points to consider when choosing plants – they should thrive on nutrient-poor soil and withstand wind, sun, frost, heavy rain and dryness. We have compiled a list of mosses, groundcover plants and grasses that are particularly suitable for house, carport or garage roofs.

Various green plants grow on the roof of a wooden building.
© Getty Images

In this article

Close-up of various Sedum plants.

The plant genus Sedum (members of which are commonly known as stonecrops) comprises 420 different species. They all store water well and can therefore survive extended periods of dryness.

1. Sun worshiping stonecrops (Sedum)

Stonecrops are ideal for particularly hot areas because they have water-storing leaves and can therefore survive long periods of dryness and frost. The plants, which are also called Sedum, exist in over 400 different species – most of which are groundcover varieties. They flower from June to August and are different colors depending on the species: the goldmoss stonecrop has star-shaped yellow flowers, for example, while the Caucasian stonecrop has white or bright pink/violet blossoms. For impatient gardeners, there are ready-made Sedum mats that can be cut and laid out as desired.

2. Bushy grasses

Whether it’s sheep’s fescue, silver grass or common quaking grass: with growth heights of 15 to 40 centimeters, bushy grasses also visually open up a roof garden. They are accustomed to dryness, easy to care for and perennial. While silver grass dies in areas with too much frost, the bluish sheep’s fescue and brownish-red quaking grass remain pretty to look at and are resistant to frost, even in winter.

3. Carnations or pinks: a sea of flowers

Various carnation-like perennials have bright colors and all the qualities that a robust roof plant needs: sea thrift (also known as sea pink) grows to a height of up to 50 centimeters, and actually comes from the salty sea coasts of the North and Baltic Seas. Consequently, it can withstand wind, dryness and rough weather in equal measure. It flowers from May to October, forming pinkish purple carpets. Maiden pink is classed as a protected species in many cantons – if you plant your roof with this beautiful local plant, you can enjoy bright pink flowers from June to August – and help support biodiversity in Switzerland.

Sea thrift (or sea pink) grows extensively on the roof of a house

For roof greening, you need plants that can thrive in specific conditions – such as sea thrift (or sea pink)

4. Moss for a low roof load

Has a structural engineer or building expert inspected your roof and come to the conclusion that the permissible roof load will not support lush vegetation? Mosses are a good alternative in this case. They are less effective than other plants for insulating and cooling, but usually weigh only 50 to 60 kilograms per square meter when damp. By way of comparison, a roof must be able to bear loads of over 100 kilograms per square meter for intensive roof greening projects – such as herb gardens or family gardens where the whole family can sit comfortably out on the roof together. Moss mats available from specialist shops can be quickly cut to size and laid. From the first day on, they offer a green eye-catching feature – even in winter.

5. A spot of color from a bulb

Whether you prefer tulips, crocuses, daffodils or grape hyacinths – their bulbs need no more than ten centimeters of plant substrate, i.e. earth or fine gravel, to grow. These dashes of spring color are often perennial and can be spread at will over grasses, mosses and groundcover plants. The flowers that bloom on low garage or carport roofs from February or March are particularly attractive.

6. Lavender and sage – a Mediterranean touch

Mediterranean plants such as wonderfully fragrant lavender and sage bushes can also be grown from a substrate height of 15 centimeters. Since both originate from the Mediterranean, the violet-flowering plants are real sun worshipers that appreciate stony soils and aridity. Both species thrive better if they are pruned back vigorously in fall or spring, so they require slightly more care than Sedum, moss and similar plants. Lavender grows to a height of about 25 to 40 centimeters, sage even up to 60 centimeters.

7. Bee food for large roofs

Due to its rapid growth, cypress spurge requires a lot of space. It is an alpine perennial native to Switzerland which has lemon yellow flowers from June to August and grows to a height of around 15 centimeters on the gravel bed of green roofs. This robust succulent plant likes it dry, sunny and stony, and is very popular with bees and bumblebees. Another plant appropriate for the quick greening of large roofs and providing food for insects is snow-in summer. The silver-leaved felt-like plant with white flowers originally comes from southern Italy and therefore grows well in hot, sunny conditions.

Lemon yellow cypress spurge grows between stones.

Cypress spurge blooms even on barren roofs. It grows quickly and looks attractive with its lemon-yellow flowers.

8. Wild herbs on top of the shed

Golden yellow chamomile, whitish violet thyme and purple wild marjoram not only bloom beautifully, but also exude a beguiling fragrance. If you plant the herbs on the low roof of a shed or carport, bumblebees and bees are not the only ones who will make the most of the wild plants: thanks to a small ladder, amateur cooks can collect ingredients directly from the herb garden on the roof – the same also applies to wild strawberries. Important: the roof must have a minimum load-bearing capacity of 100 kilograms per square meter – as a rule, this figure can be obtained from the manufacturer of the shed or carport.

9. Diversity thanks to rockery plants

Thick-leaved plants, cactus-like species or leaf succulents with flowering stems – over 450 different saxifrage or rockfoil species are available in a wide variety of shapes, sizes and colors. Most of them are robust rockery plants that thrive unassumingly and are therefore ideal for green roofs. As there is such a wide variety, the best thing to do is to stop by the gardening store and seek inspiration.

Sedum plants on a roof.

Plants for green roofs have to cope with nutrient-poor soil as well as wind, sun, frost, heavy rain and dryness.

10. Anything is possible – for the hard-working

Lush rose bushes, fruit and vegetable beds, even a complete family garden on the roof. It’s all possible. In this case, the roof greening is referred to as “intensive” due to the amount of work involved. Perennials, shrubs and vegetable plants must be regularly watered, cut and fertilized. The roof garden creates pure quality of life, but is only something for diligent amateur gardeners. If you are not afraid of the effort and are building a new house, you can plan the roof garden from the start.

Conclusion: variety to suit your taste

Whether you want to keep it simple and inexpensive or you fancy creating a lush and useful garden – the possibilities are endless and offer something for everyone. Gardening and DIY stores, or the largest gardening trade fair in Switzerland, Giardina (held in March each year at Zurich Messe), offer you the chance to marvel at all the plants and finally make your own choice.

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