Planning of Green Roofs and Green Walls

Andras Bela Olah PhDolah.andras.bela@gmail.com

Lecture 4: Growing medium and plants

Growing medium requirementsThe growing medium can not be ordinary soil in case of green roofs.

On the one hand, it must be put onto a rooftop. Thus, it must be as light as possible.

On the other hand (and this is more important) the ordinary soils can be permanently ripped or pan-breaked by digging, or even ploughing.

But these methods can not be applied on green roof. These can easily damaged the lower layers, which eventuates the necessity of total renovation of the green roof.

So, the growing medium has to be remained aerated without any pan-breaking. This requires a very special „soil” structure.

Furthermore the organic compounds of the soil must be low especially by extensive green roofs to avoid the appearance of too much weeds.

In case of intensive green roofs the situation is different due to the different vegetation.

Growing medium of extensive green roofsThe demands are the low weight, the maximum aeration together with minimal compressibility and minimal organic compound.

These requirements eventuates that ordinary good soils (i. e. chernozem) are absolutely disadvantageous, while quite extreme material can be proved excellent.

The compounds of such soils can be perlite (it is commonly used in all kind of green roof growing mediums due to its low specific weight).

Furthermore different kind of rubble (!) can be excellent.

For example brick rubble, ytong rubble (!), rubble of light stone types. Porous materials are extremely advantgeous, because they adsorbs water and that can be used up by the plants in drier periods.

In some cases there are used also slag/clinker. Its material structure is suitable, but it must be carefully applied during the design, because some kind of slag can contain poisonous heavy metals in great percentage.

Perlite

Brick rubble

Concrete rubble

Slag/clinker I.

Slag/clinker II.

Growing medium of intensive green roofsThe demands are in this case also the low weight, the maximum aeration together with minimal compressibility.

But in this case the plants are quite different, turf, shrubs and trees instead of Sedum an mosses.

On the one hand, these plants require much greater quantity of organic fertilizers, on the other hand these can provide such a covering on the growing medium, which can seriously set back the apperance of weeds.

Thus the greater rate of organic compounds is required in this case.

Furthermore there must be provided the continuous organic fertilization.

Growing medium of intensive green roofsThe demands are in this case also the low weight, the maximum aeration together with minimal compressibility.

But in this case the plants are quite different, turf, shrubs and trees instead of Sedum an mosses.

On the one hand, these plants require much greater quantity of organic fertilizers, on the other hand these can provide such a covering on the growing medium, which can seriously set back the apperance of weeds.

Thus the greater rate of organic compounds is required in this case.

Furthermore there must be provided the continuous organic fertilization.

Plants of extensive green roofsAs it was mentioned earlier these plants are the Sedum species and mosses.

In Hungary the Sedum species are dominant.

Besides them only some Saxifraga species can be remarkable, not mosses.

Sedums are perennial leaf succulents. This means that they can bear very long arid periods without irreversible damages.

Mosses are dominant among more humid climate circumstances.

For example in Germany mosses and Sedum are equally dominant.

As it was discussed, by oceanic climate the turf/sod vegetation layers can be also considered as extensive.

Moreover by rainforest climate the usage of trees and shrubs can be planted onto extensively maintained green roofs.

Plants of extensive green roofsAs it was mentioned earlier these plants are the Sedum species and mosses.

In Hungary the Sedum species are dominant.

Besides them only some Saxifraga species can be remarkable, not mosses.

Sedums are perennial leaf succulent. This means that thy can bear very long arid perios without irreversible damages.

Mosses are dominant among more humid climate circumstances.

For example in Germany mosses and Sedum are equally dominant.

As it was discussed, by oceanic climate the turf/sod vegetation layers can be also considered as extensive.

Moreover by rainorest climate the usage of trees and shrubs can be planted onto extensively maintanied green roofs.

Plants of extensive green roofs (experimental research „roofs”)

As it was mentioned earlier these plants are the Sedum species and mosses.

In Hungary the Sedum species are dominant.

Besides them only some Saxifraga species can be remarkable, not mosses.

Sedums are perennial leaf succulent. This means that thy can bear very long arid perios without irreversible damages.

Mosses are dominant among more humid climate circumstances.

For example in Germany mosses and Sedum are equally dominant.

As it was discussed, by oceanic climate the turf/sod vegetation layers can be also considered as extensive.

Moreover by rainorest climate the usage of trees and shrubs can be planted onto extensively maintanied green roofs.

Plants of intensive green roofs

Requirements: -They have to bear the windy situation and the low relative air humidity.-They have to bear frost.-They have to provide surface covering for a long time.-They must be eurytopic.

There must not be used the following kind of plant species:-Plants with agressive roots (i. e. Phyllostachis sp./bamboo)-Fast growing, huge plants with relatively fragile branches (Salix sp./ willows, Populus sp./poplars, greater Acer sp./maples).-Oversensitive plants (plants with requirements of great relative air humidity i. e. japanese plants)-Oversensitive plants (extremely injurable by some insects)

Plants of intensive green roofs

Requirements: -They have to bear the windy situation and the low relative air humidity.-They have to bear frost.-They have to provide surface covering for a long time.-They must be eurytopic.

There must not be used the following kind of plant species:-Plants with agressive roots (i. e. Phyllostachis sp./bamboo)-Fast growing, huge, with relatively fragile branches (Salix sp./ willows, Populus sp./poplars, greater Acer sp./maples).-Oversensitive plants (plants with requirements of great relative air humidity i. e. japanese plants)-Oversensitive plants (extremely injurable by some insects)

Plants of intensive green roofs

Requirements: -They have to bear the windy situation and the low relative air humidity.-They have to bear frost.-They have to provide surface covering for a long time.-They must be eurytopic.

There must not be used the following kind of plant species:-Plants with agressive roots (i. e. Phyllostachis sp./bamboo)-Fast growing, huge, with relatively fragile branches (Salix sp./ willows, Populus sp./poplars, greater Acer sp./maples).-Oversensitive plants (plants with requirements of great relative air humidity i. e. japanese plants)-Oversensitive plants (extremely injurable by some insects)

Plants of intensive green roofs

Requirements: -They have to bear the windy situation and the low relative air humidity.-They have to bear frost.-They have to provide surface covering for a long time.-They must be eurytopic.

There must not be used the following kind of plant species:-Plants with agressive roots (i. e. Phyllostachis sp./bamboo)-Fast growing, huge, with relatively fragile branches (Salix sp./ willows, Populus sp./poplars, greater Acer sp./maples).-Oversensitive plants (plants with requirements of great relative air humidity i. e. japanese plants)-Oversensitive plants (extremely injurable by some insects)

Plants of intensive green roofs

Requirements: -They have to bear the windy situation and the low relative air humidity.-They have to bear frost.-They have to provide surface covering for a long time.-They must be eurytopic.

There must not be used the following kind of plant species:-Plants with agressive roots (i. e. Phyllostachis sp./bamboo)-Fast growing, huge, with relatively fragile branches (Salix sp./ willows, Populus sp./poplars, greater Acer sp./maples).-Oversensitive plants (plants with requirements of great relative air humidity i. e. japanese plants)-Oversensitive plants (extremely injurable by some insects)

Plants of intensive green roofs

Requirements for design:

The design must provide tha maximal protection against wind. This means that smaller greater shrubs (even hedge) should be planned next to the edges of the roof and greater plants (trees) ought to be planned only in the inner parts.

In the ideal case there is a cooperation between the garden designer and the architect and there appears such building structures, which can provide the necessary wind protection to the plants (and also to the users and visitors) of the intensive green roofs.

These architectural elements can be glass walls, higher parapets/breast walls, or simply created a peripteral (or even dipteral) architectural space on the rooftop, where the columns provide the necessary wind protection (i. e. Vancouver Public Library).

Plants of intensive green roofs

Requirements for design:

The design must provide tha maximal protection against wind. This means that smaller greater shrubs (even hedge) should be planned next to the edges of th roof and greater plants (trees) ought to be planned only in the inner parts.

In the ideal case there is a coopertion between the garden designer and the architect and there appears such building structures, which can provide the ncessary wind protection to the plants (and also to the users and visitors) of the intensive green roofs.

These architectural elements can be glass walls, higher parapets/breast walls, or simply created a peripteral architectural space on the rooftop, where the columns provide the necessary wind protection (i. e. Vancouver Public Library).

Thank you for your attention!