High Vertical Greening -- over 5 meters (16.5 ft)

In the course of converting a factory from the Wilhelminian era into flats, an atrium was cut into the building, where so-called ‘lofts’ were created with arcades and open staircases on eight floors or four double floors. To prevent the newly created, narrow inner courtyard from looking like a prison, it was clear from the outset that greenery would have to be planted 20 metres high. And it worked! The climbing plants were planted in a presumably lush layer of substrate on the roof of an underground car park. They were Akebia (Akebia quinata), Pipevine (Aristolochia macrophylla) and Kiwi (Actinidia chinensis), which according to the FLL guidelines are only expected to reach heights of 8 - 10 metres. These three species grew more than twice as high at that location! Presumably because the water supply via irrigation is really good and because the plants are still protected even at this height and the wind doesn't ‘blow the soul out of them’.

There was the beautiful but dilapidated ‘Saxon House’ inn, which characterised the townscape and which people were afraid to demolish. In the end, permission was granted in 2006, but the old hipped roof was to be rebuilt: As a greened steel skeleton above a small, flat new building housing a snack bar. Pipevines (Aristolochia macrophylla) were supposed to take over the greening, but for 15 years now they have only been growing 3 - 4 metres high. They practically don't grow into the steel frame at all, and yet everything was so beautifully planned! Presumably, however, nobody calculated how much water such a green roof would evaporate every day and how much water would have to be provided as a result. Perhaps irrigation was even planned and was ultimately saved.

In a nutshell: it didn't work. The plants ‘realise’ that the wind is blowing the water out of their leaves and they simply stop growing. To make matters worse, grasses and maples have now also settled in the planting bed and have not been removed. They are very assertive and compete with the pipevines for the already small portions of water, for example during the morning dew. In hindsight, everyone is usually smarter, and so it could also be said for this object that pipevines were perhaps too demanding. Clematis vitalba, Clematis montana or maiden vine (Parthenocissus quinqefolia) would certainly not have covered the roof completely, but they would probably have grown to the desired height and broken up the hard structures of the steel roof a little...

As already mentioned, water and wind probably play the biggest role here. Wind actually always inhibits growth. In structural analysis, ‘increased wind loads’ must be taken into account from a building height of 5 and 8 metres, which confirms that more wind blows higher up. Wind-protected locations, on the other hand, i.e. courtyards or an atrium, allow the plants to grow very tall!

Water increases the growth height if it is available and can be stored in the soil. Particularly tall specimens of climbing plants can often be seen in the lower part of cities that were situated along a river, i.e. in ‘floodplain’ locations. This is certainly related to a high groundwater level. The important question is whether artificial irrigation is sensible and affordable. In the case of apartment blocks, it is often more sustainable to give a pensioner in the building a 30 euro rent reduction per month and in return give them personal responsibility for watering a green façade.

Now to the soil: It should be loose and humus-rich and have a neutral pH value. It must also be permeable downwards, as waterlogging is fatal for many climbing plants. Soil compaction and ‘weed’ growth are also bad. The best soil is (regularly maintained) open soil or a mulch cover that does not pull the pH value into an acidic environment. Nitrogenous fertiliser can also work wonders.

Sunlight and the associated warmth initially promote growth, but this quickly leads to evaporation stress, which in turn restricts height growth. Bright, ‘sunny’ (north-facing) locations are therefore more favourable, although some climbing plants will then also wither in the lower areas.

High facade gardens can be created with or without a support system. In the first case, the aim is to achieve a big effect with little effort. Self-clinging climbers, like English ivy and Boston ivy, are a logical choice. To avoid structural damage, many builders resort to climbing plants that are "tamed" by trellises. Whether the taming and shaping of a plant really takes place depends on its maintenance. The following plants are suitable: hops, akebia, Dutchman's pipe, clematis vitalba, and 'wild' (fruitless) vines. Vigorous twiners like wisteria, fleece vine, and bittersweet need lots of maintenance. If unkempt, these plants accumulate masses of dead and dry foliage that, when close to windows, can be a fire hazard. In case of the freezing-over of wet foliage, these plant masses can be a heavy load spreading across the entire surface, endangering the stability of the system or support. When in doubt, forego vigorous climbing (twining) plants.

Ivy ‘Woerner’ grows to a height of around 20 metres, but the water supply must be right. Excessively hard frost, especially at higher (mountain) altitudes, is also damaging, as the areas that have already been established will freeze back down several metres. In general, ivy greening takes a very, very long time. It can take 25 years for a house gable to be completely overgrown, and it is often only then that it has to be cut back to keep the roof edge clear, etc.. However, if there are windows in the façade, it constantly takes a lot of time and effort to cut them free.

The species Parthenocissus quinqefolia is ‘not fish and not meat’. It is not really suitable as a self-climber because of the rather weak adhesive discs, as the plants are quickly torn off by the wind at greater heights. And it is not suitable for climbing aids either, because it also forms these adhesive discs and then grows somewhere else, i.e. does not stay in the given climbing area. But this plant is strong-growing - that's its value! If you regard it as a self-climber and provide it with some cross ropes in the upper areas as ‘fall protection’, you can create magnificent greenery with little effort, and with red autumn colouring to boot. The species grows quite quickly and up to 30 metres high, but is ‘negatively phototropic’, meaning it creeps into crevices, which can lead to structural damage.

Parthenocissus quinqefolia ‘Engelmannii’, on the other hand, is a good self-climber, growing to a height of around 20 metres. It grows quickly and can green a wall in 4 - 10 years.

Three-lobed wild vine (Parthenocissus tricuspidata ‘Veitchii’) grows to a height of 15 - 20 metres and grows moderately to quickly, but it takes a few years to cover a high wall.

The care requirements for all these wild vines are as described under ‘Ivy’.

Asian wisterias grow to around 15 metres, varieties of Wisteria floribunda or similar hybrids to 22 metres or even, as in Bonn on the corner of Koblenzer Strasse and Friedrichallee, to 30 metres. The specimen there (presumably W. floribunda ‘Macrobotrys’) is probably one of the tallest ground-bound greenings, especially in an unprotected location fully exposed to the wind! Blue roses grow extremely quickly, namely 3 - 6 metres per year, almost as fast as knotweed. On the one hand, they are flowering plants, but in order to enjoy this aspect, they should be pruned twice a year, which is very time-consuming and tends to prevent tall greenery. On the other hand, blue reeds are also TOP green plants, i.e. species for real façade GREENING. If this aspect is in the foreground, one cut per year is sufficient and later, after the end of the vital and vigorous youth phase, one cut every two years may be sufficient.

This pipevine grows to a height of 10 metres, or 15 - 22 metres in sheltered locations (see above). But: It can take 10 - 15 years to grow a pipevine to a height of 10 metres, even under good conditions. Well, the time can be shortened a little with large, expensive solitary plants. In any case, this type of planting is very sustainable, as pipevines hardly need pruning, perhaps once every 4 - 8 years. This is due to the fact that the vigour is not expressed in the growth of shoots, but in the large leaves that fall off every autumn.

This Akebia usually grows to a height of 10 metres, but can also reach 20 metres, see the ‘positive’ example above. It is just as valuable as the pipevine, even semi-evergreen and deserves to be propagated. It usually grows faster than pipevine, so it doesn't take 10 years to grow to a height of 10 metres. However, it should perhaps be pruned a little more often, i.e. once every 2 - 3 years, to prevent excessively lush foliage.

Silver Lace Vine grows to a height of 10 - 15 metres. However - and this is where knotweed differs from all other plants - it can sometimes reach these 15 metres in just 2 years! This can be very beneficial for outdoor catering. Of course, huge amounts of shoots and green mass are then also formed if the water supply is optimal. This means that the annual pruning effort is quite high, and pruning less than once a year is not recommended. In other words, a plant for ‘quick greening’!

According to the FLL guideline, kiwi grows to a height of approx. 10 m, but sometimes also 20 m, see above. The speed of growth and growth habit are comparable to that of blue rain, which means that pruning measures are also required. However, the kiwi grows very ‘expansively’, forms very spreading foliage rollers and is therefore difficult to control and only suitable for high greening to a limited extent.

This bittersweet grows to a height of 14 metres. The plant grows very vigorously at first, 2 - 4 metres per year, but this calms down after a few years. This means that pruning every 1 - 2 years should be sufficient. The tree shrike thus offers a compromise between rapid growth and little pruning. The second species, Celastrus scandens, probably only grows to a height of 10 metres.

This clematis grows up to 14 metres high on façades and up to 20 metres in the wild (in alluvial forests). The species grows 1 - 2 metres per year, even with an insufficient supply of water, and is very drought-resistant. However, the vegetation often does not look lush and dense, but a little thin and shaggy. Pruning every 2 - 3 years should be sufficient.

The varieties of Clematis montana can reach 10 metres, or even 15 metres in sheltered locations. The plants grow moderately quickly and pruning every 2 to 3 years should suffice if necessary.

In addition to the usual loads caused by cable tension, plant weight, etc.., wind 'loads' must also be taken into account: after growing about 8m high, plants become 'wind catchers,' especially at the upper corners of buildings. Instead of using plastic fittings (rawl plugs) here, composite mortar or metric fittings would be better. Particularly at risk again are vigorously-growing plants with thick foliage that are not trimmed regularly, as they then offer an inviting surface for winds to strike.

Vandalism can be expected if greening is done in rough neighborhoods of a city or in areas which are hard to supervise. For this reason, FassadenGrün recommends first and foremost rope systems in the heavy and massiveconstruction styles. To prevent the stepping and weight support for potential vandals -- the "ladder effect" -- use horizontal ropes or other trellis elements starting only at a height of about 1.8 metres, or even 2.5 m, as described for cable system 4030. If required, the plants can then be trained with strong bamboo sticks.

High climbing systems made of metal may need to be attached to the lightning protection system of a house or building, if such exists and is required. This is all the more so if the metal trellis structure:

 • is massive and rises up to roof height  

 • is on a building which is exposed to lightning strikes  

 • is located on a building that towers over others, or otherwise is exposed to lightning and is made of combustible materials, like wood.

For the lighter trellises from FassadenGrün, a lightning conductor is usually unnecessary, nor are they usually needed with awnings, letterboxes, signposts, and cornice covers made of sheet metal. When in doubt, ask an expert or specialist planner.

Private small-home builders and contractors are well advised to do without a high vertical greening when there are any doubts, or to green only up to about 5 metres high, as here assembly and maintenance can be carried out by means of a single ladder. If professional planning, structural calculation, and all subsequent costs are ensured, however, nothing stands in the way of higher greenings!