Greening in shelf construction

Who needs these green spaces and how much do they cost?

‘Shelving systems’ meet high ecological standards in densely populated areas. The concept is suitable for prestigious buildings, city centre locations, company headquarters or simply anywhere where green privacy screening is desired. The investment costs can range from 450 to well over 1,000 euros per square metre of green space (as of 2020).

A price example in the high-end, upper range: Around 2020, a price of €1,200 gross per square metre of green space was quoted here for 150 square metres of green space, plus brackets or pergolas, technical room and scaffolding.

As with a shelf, the greenery is arranged in several layers, on several ‘shelf boards’, usually in plant troughs set up there and often with automatic irrigation. The greenery is fully present immediately or after a few weeks/months. What’s more, depending on the mix of plants, such green spaces look surprisingly good even in winter, so they are certainly ‘evergreen’.

Sometimes, because of the greening, the building needs its own construction level in front of the façade in a pergola design for the installation and maintenance of the plant troughs, and then it becomes really expensive. However, if the building already has pergolas, these can often be greened at low cost. However, they must be wide enough for escape routes AND plant pots and, if necessary, be reinforced for the installation of heavy pots.

The plants can grow downwards or climb upwards on wire ropes and trellis bars.

The more green mass is produced and has to be removed by pruning, the higher the maintenance costs. A mix of different plants in a small space requires specialist staff for pruning and maintenance, which may increase costs further.

The ‘Calwer Passage’ pilot project in Stuttgart

Planned by the client, “Ferdinand Piëch Holding GmbH”, and the architect Christoph Ingenhoven as a flagship project, this green façade – which cost several million euros – has exceeded virtually all expectations. Nothing was left to chance during the preparatory phase either! Plants were tested on sample walls for all four cardinal directions.

Als feststand, was zueinander passt, wurden die Pflanzen in mehr als eintausend großen “Inlay”-Trögen monatelang in einer Gärtnerei vorkultiviert, bis sie schließlich 2022 per Kran in die Metallkübel der Fassade eingeschwenkt und an die Bewässerung angeschlossen wurden. Diese wiederum erkennt per Sensor Außentemperatur und Feuchtegrad in den Kübeln und kann somit maßgenau arbeiten…

Der Anteil unserer Firma “FassadenGrün” am Projekt ist vergleichsweise bescheiden und besteht in der Zulieferung von Kleinteilen für die Rankseile.

Fazit: Auch wenn dieses geniale Projekt kaum reproduzierbar ist, wird es Anregung für alle künftigen Vorhaben dieser Art geben!

Greening in spring 2024 at the ‘Callwer Passage’ in downtown Stuttgart / Baden-Württemberg

This photo gallery attempts to show the many plants used in the pilot project and their respective design effects. Unless otherwise noted, the photos were taken in early April 2024.

The ‘Calwer Passage’ with long, overhanging plant shoots in autumn, before pruning (end of October 2023) in Stuttgart / Baden-Württemberg

The ‘Calwer Passage’ with long shoots (ornamental vine “Inserta” - Parthenocissus inserta) at the end of October 2023 in Stuttgart / Baden-Württemberg

The same spot as in the previous photo, but now after the plant shoots have been cut back in spring (Aprill 2024). ‘Calwer Passage’ in Stuttgart / Baden-Württemberg

The Calwer Passage with new shoots in spring (April) in the centre of Stuttgart / Baden-Württemberg

The ‘Callwer Passage’ in spring 2024 in Stuttgart / Baden-Württemberg

Callwer Passage: Here, the technical structure of the ‘shelves’ is clearly visible: rows of plant troughs and mesh panels to walk along. On the right, you can see ivy (Hedera helix), among other things. Stuttgart / Baden-Württemberg

This greenery thrives on the interaction of a wide variety of plants. Callwer Passage in Stuttgart / Baden-Württemberg

From bottom left to right: Cotoneaster “Coral Beauty”, Lonicera henryii, Parthenocissus inserta, Lonicera henryii. Callwer Passage in Stuttgart / Baden-Württemberg

Cotoneaster “Coral Beauty” at the Calwer Passage in Stuttgart / Baden-Württemberg

Here, the overhanging vegetation is mainly produced by creeping cotoneaster, presumably of the “Skogholm” variety. Callwer Passage in Stuttgart / Baden-Württemberg

After pruning in spring, the following hanging plants can be seen: top left, Clematis alpina (fresh light green); right, ivy (Hedera helix) with dark green leaves; and in between, a few lighter shoots of winter jasmine (Jasminum nudiflorum). Callwer Passage in Stuttgart / Baden-Württemberg

New greenery in early spring: bottom left Clematis alpina, centre of image Virginia creeper “Inserta” (Parthenocissus inserta), top right Japanese knotweed (Polygonum aubertii), bottom right Vinca major. Callwer Passage in Stuttgart / Baden-Württemberg

Top left: Hedera helix; top centre: two climbing ropes with Parthenocissus inserta; to the right of these: a clematis; bottom centre: Jasminum nudiflorum; top right: Vinca major. Callwer Passage in Stuttgart, Baden-Württemberg

Centre: Clematis alpina, top right: Vinca major, bottom right: Cotoneaster “Coral Beauty” with red berries. Callwer Passage in Stuttgart / Baden-Württemberg

Left: Parthenocissus inserta, centre: Lonicera henryii, right: Cotoneaster. Callwer Passage in Stuttgart / Baden-Württemberg

The low purpleberry (Symphoricarpos chenaultii “Hancock”) at Callwer Passage in Stuttgart, Baden-Württemberg

Plants for greening in shelving systems

Evergreen plants are of course desirable here, but deciduous species are often more attractive. A mixture of both can achieve great effects. Species with weak to moderate growth are preferable, as this limits the amount of maintenance (pruning) required. Tangled thickets and knots should be avoided! Species such as hops, which produce a lot of dead plant shoots, should also be avoided, as they form ‘dead wood’ and may then become a ‘fire hazard’.

Overall, growing plants in pots is a challenge, and not all plants like it. However, the species listed below have proven themselves, without this being an exclusion criterion. Many can be seen in the photos.

Twining plants: Wisteria, Evergreen honeysuckle, Japanese honeysuckle, Tellmann's (Gold) Honeysuckle, climbing knotweed, ornamental vine ‘Kolomikta’, Periploca, Akebia, Schisandra, Menispermum, Aristolochia tomentosa, Trachelospermum jasminoides

Stem Tendril Climbers: Thicket creeper, grape-free wild vine, True grapevines (Vitis), Ampelopsis

Leaf stalk climbers: Clematis alpina, Clematis tangutica, Clematis montana

Spreading climbers: Winter jasmine

Hanging plants: Ivy, thicket creeper, winter jasmine, cotoneaster “Coral Beauty” and “Skogholm”, large-leaved periwinkle (Vinca major), low purpleberry (Symphoricarpos chenaultii “Hancock”)

Greenery in a ‘shelf’ design, clematis on climbing ropes

Combination with plants from the ground

Greenery in a ‘shelf construction’ can be combined with classic, ground-based greenery! Even though this approach was not taken in the above-mentioned pilot project... The ‘base load’ of greening can come from plants growing in the ground below, possibly with the prospect of having to wait several years for success and the desired greening heights. Shelf greening is immediately visible, even in the first year, ultimately enhancing the appearance and adding additional accents such as flowers, etc.

Classic ground-based greenery (ivy – Hedera helix) combined with plant troughs at the top of the pergolas

Pros and cons of ‘automatic watering’

An automatic watering system, ideally combined with fertilisation, is expensive but sustainable, because as long as it works, the plants remain green and healthy. The costs involved are correspondingly high. For large green spaces, however, an automatic watering system is significantly more cost-effective when its price is calculated per square metre. Of course, such a system also needs to be maintained to prevent the pipes from becoming clogged with limescale, to ensure that watering continues even in winter, and so on. But let’s be clear: automatic irrigation is the best solution!

Um diese teure Haustechnik einzusparen, kann die Bewässerung und Pflege der Kübel natürlich auch durch die Nutzer erfolgen, vor allem im Wohnungsbau. Was nach unseren Erfahrungen allerdings nicht funktioniert, ist, dass VIELE Akteure einzelne Kübel, Begrünungs-Abschnitte oder auch Pflegeintervalle betreuen. Günstiger ist EIN Verantwortlicher für die gesamte Begrünung, für alle Kübel usw.. Das kann ein Ruheständler im Haus sein, der für das Gießen einen Mietnachlass bekommt, oder auch ein Hausmeister.

Oder: Jeder Nutzer bekommt seinen eigenen Pflanzkübel, z. B. auf einem Balkon. Dazu können voluminöse (also nicht zu kleine) Pflanzgefäße bereits in die Architektur integriert werden und dann in die Verantwortung der Bewohner übergehen.

Such large planters do not necessarily require automatic watering, and even manual watering can be neglected for a few days.... Climbing plants Schisandra (front) and ornamental vine ‘Kolomikta’ (Actinidia kolomikta)

Problems and risks associated with greening in shelving systems

Vertical greening systems are based on pots or containers in which the plants grow. Or perhaps not, which brings us back to the first problem: it sometimes happens that, after 1–2 years, such greenery still does not come close to the desired foliage mass that was originally predicted.

This is linked to the botanical species used: some plants simply do not grow as luxuriantly when grown in containers, and this must be taken into account in advance. In other cases, several different species may not be compatible when grown in the same container. In very demanding projects such as the “Calwer Passage” shown here, plant communities are therefore tested for compatibility beforehand.

Even well-intentioned additions of grasses and the like are best avoided. These are aggressive ‘weeds’ that take energy and, above all, water away from almost every climbing plant, for example by absorbing morning dew.

Even the direction of the sun can play a role: planters on hot south-facing sides heat up considerably, and the roots of some plants clearly do not like this. All these problems are familiar from “ground-based” greening schemes using planters, so the experience gained there must be taken into account.

Diminishing vitality is also frequently observed: once lush greenery suddenly appears less dense and rather “sparse” in subsequent years. Here, corrective action may be possible through fertilisation and a (partial) replacement of the substrate. If, on the other hand, the shoots become bare, e.g. in honeysuckle (Lonicera), this is again species-specific and can hardly be influenced by fertilisation. Unfortunately, shade also promotes this bare growth; such species should perhaps not be used in the first place.

Weakened plants, on the other hand, die more quickly from frost; such losses must be replaced, otherwise gaps will appear in the greenery! And it surely goes without saying that the irrigation system must function and be regularly maintained. Without sufficient water, such greenery simply won’t thrive!