Plants suitable for rooftop greening

table of contents

1. Rooftop greening system infrastructure design
2. Points to consider when selecting plants for rooftop greening
3. Plants suitable for rooftop greening ① - Grass
4. Plants suitable for rooftop greening② - Ground cover plants
5. Plants suitable for rooftop greening ③ - Shrubs/medium-sized trees/tall trees

1. Rooftop greening system foundation design

KYODO KY-TEC's rooftop greening system offers a high degree of flexibility, allowing you to design the most optimal rooftop greening specifications while minimizing the burden on the building, depending on the design situation and construction conditions.In addition, when designing a garden with medium and tall trees, the soil thickness and load capacity will vary depending on the garden design, so calculations are required.
Below are the foundation configurations for conventional construction methods and for when using a rooftop greening system.

• Conventional construction method

  

  The conventional method involves layering soil on top of a greening foundation (root barrier, water retention and drainage layer, filter layer, etc.). This method is characterized by the fact that the soil becomes thick, which increases the load. Also, care must be taken to ensure that the root barrier is properly installed, as it can damage the waterproof layer.

• Rooftop greening system

  

  Kyodo KY-TEC's rooftop greening system (Square Turf Light) has a water storage tray that collects rainwater, which increases water retention and allows plants to grow in a thin layer.In addition, because the soil is stored inside the container, there is no strain on the waterproof layer.

Considerations when designing a green roof

1) When considering rooftop greening, we will mainly check the following items.

• Purpose and use of greening

• Required green area

• Height of installation location

• Roof Shape

• position

• Movable load

• Waterproof specifications

• Drainage facilities (drain location)

• Availability of air conditioning and other equipment

• Power and water supply equipment

2) Based on these, we will create a plan.

Relationship between planting and soil thickness

The selection and placement of plant species, as well as the size of the plants, are important elements in greenery design. When planting trees, the appropriate soil thickness must be ensured. Ensuring the appropriate soil thickness is important depending on the species being planted, and the load varies proportionally. KYODO KY-TEC products have high water retention thanks to their water storage function and automatic irrigation, allowing for a minimum soil thickness. However, conventional construction methods require a large-scale greenery system that requires a heavy load, taking into account the soil thickness according to the root ball of the plant and the storage and drainage function.

• 

  Conventional construction methods require a thick soil thickness due to water retention. This not only affects the load capacity, but also means that the soil is very thick and heavy, so waterproofing repairs, restoration, and removal are expected to be quite costly.

• 

  The rooftop greening product system can be installed with a minimum soil thickness due to its structure and features. This reduces the load on the structure and also makes it easy to restore the system when waterproofing is repaired.

2. Key points to consider when selecting plants for rooftop greening

Most plants can be planted in rooftop greening systems, but for plants to grow normally, it is important to select plants that are suited to the vegetation environment and management conditions in which they are planted. Here we will introduce some points to pay particular attention to when selecting plants for the special environment unique to rooftop greening.

We also have a column that will be helpful when designing rooftop greenery, so please take a look.

3. Plants suitable for rooftop greening ① - Grass

When planting a regular rooftop greenery or a legal greening scheme, we recommend planting a grass species like Korean grass, which allows for labor-saving maintenance. KYODO KY-TEC offers the following grass species. Each type of grass has different characteristics and maintenance methods, so please check the type of grass before installing it, and feel free to contact us with any questions.

All Japanese grasses are warm-season types, but there are cool-season and warm-season types of Western grasses, and Kentucky bluegrass belongs to the cool-season type of Western grasses.
Examples of warm-season western grasses include Bermuda grass.

• Korai Grass (Zoysia)

  

  sunshine environment	Hinata
  Viewing period	July ~ August
  Evergreen/Deciduous	Fallen leaves
  Ease of management	〇
  Features	Korean grass, considered the representative of Japanese grass, is the most widely used grass in Japan from the Tohoku region southward and is suited to the Japanese climate. Compared to other grasses, it has excellent shade and moisture tolerance and can withstand trampling. Because it has narrow leaves and a high density, regular mowing and careful maintenance will help create a beautiful lawn.

• Noshiba (Zoysia Japonica)

  

  sunshine environment	Sun to partial shade
  Viewing period	July ~ August
  Evergreen/Deciduous	Fallen leaves
  Ease of management	〇
  Features	Its advantage is that it has a high self-sprouting rate among Japanese grasses and is close to the wild species. Its leaves are tough, resistant to foot pressure, and resistant to pests and diseases, making it popular on golf courses and parks. The leaves that grow are large and coarse, measuring over 4mm wide, and it grows relatively slowly, making it less likely to become densely packed. On the flip side, it does not require as much time for maintenance as Zoysia grass.

• Low-maintenance grass - Mijoka (registered variety)

  

  sunshine environment	Hinata
  Viewing period	July ~ August
  Evergreen/Deciduous	Fallen leaves
  Ease of management	◎
  Features	Traditionally, when landscape is a priority, korai grass requires mowing about four times a year, but the low-maintenance "Mijoka" grass is super dwarf, growing only about 5cm per year, so a beautiful landscape can be maintained with mowing only once every two to three years. "Mijoka" has very fine leaves, about half the size of korai grass. The short internodes also result in a highly elastic and dense turf.

• Kentucky bluegrass (Western grass)

  

  sunshine environment	Hinata
  Viewing period	All Year
  Evergreen/Deciduous	evergreen
  Ease of management	△
  Features	This variety is cold-resistant and suitable for planting in mild climates between 15°C and 25°C. It has also been used in Hokkaido. Its ability to maintain its green foliage even in winter and its ability to withstand trampling makes it popular in parks and golf courses. Because it is a cold-climate variety, it may wither in areas where temperatures exceed 30°C for several days in the summer. It also grows faster than Japanese grasses such as Zoysiagrass, requiring frequent mowing and more maintenance.

4. Plants suitable for rooftop greening ② - Ground cover plants

• Dwarf Lilyturf (Ophiopogon japonicus)

  

  sunshine environment	Partial shade to shade
  Flowering time	All Year
  Evergreen/Deciduous	evergreen
  Ease of management	◎
  Features	This versatile perennial can be used to edge flower beds, decorate the base of trees, or as a leaf plant in a mixed planting. It does not grow tall, making it easy to maintain.

• Fukisou

  

  sunshine environment	Partial shade to shade
  Flowering time	All Year
  Evergreen/Deciduous	evergreen
  Ease of management	◎
  Features	This plant is easy to use as a greening material in semi-shaded areas such as around buildings or in the shade of trees. It is evergreen, maintaining the same appearance all year round, requiring almost no maintenance, and spreading out in a mat-like pattern without disturbing the plant's appearance.

• Huiriya Bran

  

  sunshine environment	Partial shade to shade
  Flowering time	July ~ August
  Evergreen/Deciduous	evergreen
  Ease of management	〇
  Features	This is a modified variety of Liriodendron gracilis. It is a popular tree species with variegated leaves that give it a bright impression. It produces small flowers in summer and fruits from autumn to winter.

• Rosemary

  

  sunshine environment	Hinata
  Flowering time	Year-round (depending on variety)
  Evergreen/Deciduous	evergreen
  Ease of management	◎
  Features	It is a cute plant that blooms continuously with many small flowers during the flowering season. By choosing the right species, it is an easy-to-grow herb that can be used for container cultivation, hanging training, ground cover, etc. Rosemary is very hardy and can grow even in dry, poor soil. It can also withstand strong winds, making it an easy-to-grow plant that is also used for rooftop greening.

Plants suitable for rooftop greening ③ - Shrubs/medium-sized trees/tall trees

• Asebi

  

  sunshine environment	Shade to sun
  Flowering time	July to August
  Evergreen/Deciduous	evergreen
  Ease of management	◎
  Features	It can grow in the shade and is tolerant of both heat and cold, making it popular as a plant for rooftop greenery. It blooms from February to mid-April, with small white or reddish-purple flower clusters that hang like bells from the branches, and its appearance is even used as a seasonal word in the Manyoshu.

• Filifera Aurea (Golden Threadleaf False Cypress)

  

  sunshine environment	Partial shade to full sun
  Viewing period	All Year
  Evergreen/Deciduous	evergreen
  Ease of management	〇
  Features	With golden, drooping leaves all year round, this is the most popular coniferous tree for colorful ground cover. In sunny areas, it turns brown in winter, creating a striking color, and is often used for rooftop greenery. It is soft and gentle to the touch. Another feature is its relative resistance to dryness.

• Satsuki azalea

  

  sunshine environment	Partial shade to full sun
  Viewing period	May to June
  Evergreen/Deciduous	evergreen
  Ease of management	〇
  Features	The actual flowering period varies depending on the region and environment, but it usually blooms from May to mid-June. The flowers are small compared to other azaleas, but the beautiful pink and crimson-purple flowers bloom all over the branches. This plant is well adapted to urban environments, and is also used as a roadside tree.

• Indian Hawthorn (Rhaphiolepis indica)

  

  sunshine environment	Partial shade to full sun
  Viewing period	All Year
  Evergreen/Deciduous	evergreen
  Ease of management	◎
  Features	It grows naturally in many areas near the coasts of warm regions, and is distributed over a wide area outside of Japan, including Southeast Asia and East Asia. It is often used as a street tree or park tree, taking advantage of its resistance to sea breezes and air pollution. Its branches and leaves grow regularly, and its tree shape is naturally shaped. It also grows slowly, so it is used as a plant for rooftop greenery.