The document discusses the requirements for growing mediums and plant selection for extensive and intensive green roofs. For extensive green roofs, the growing medium must be lightweight, well-draining, and low in organic content to avoid weeds. Recommended materials include perlite, brick rubble, and slag. Sedum species and mosses are suitable plant selections as they can withstand long dry periods. For intensive green roofs, the growing medium requires greater organic content to support trees, shrubs and turf. Plant selections must be durable in windy and dry conditions without aggressive roots or fragile branches. The design should provide wind protection through architectural elements like walls or columns.

1. Planning of Green Roofs and Green Walls
Andras Bela Olah PhD
olah.andras.bela@gmail.com

2. Lecture 4: Growing medium and plants

3. Growing medium requirements
The 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.

4. Growing medium of extensive green roofs
The 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.

5. Perlite

6. Brick rubble

7. Concrete rubble

8. Slag/clinker I.

9. Slag/clinker II.

10. Growing medium of intensive green roofs
The 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.

11. Growing medium of intensive green roofs
The 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.

12. Plants of extensive green 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 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.

13. Plants of extensive green 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.

14. 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.

15. 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)

16. 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)

17. 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)

18. 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)

19. 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)

20. 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).

21. 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).

22. Thank you for your attention!