Climbing plants, grapevines and espalier fruit have quite specific requirements as to where they grow, ie location and aspect. The following text describes the determining factors for successful façade greenings in Central Europe. Based on this information you can assess yourself the position and aspect of your garden, select the most suitable Climbing Plants or, if necessary, adjust some of these factors in order to let a preferred plant species thrive even in a less than optimal location.
Plants need light to develop flower buds. Just as importantly though, they need the heat radiated from the sun: full sun on a tiled wall creates a microclimate which will produce an abundance of flowers and fruit in your plants, the like you will not get in a freestanding position. At the same time, the wall stores this heat and emanates it during the evening hours, which further promotes the ripening of the fruit. In timber houses and houses with external heat insulation, this "oven" effect also exists, although to a significantly lesser degree.
Unfortunately, a lot of heat also increases the evaporation rate, hence the water use. Furthermore, some plant species become very susceptible to fungal attack under heat-stress.
In order to establish the duration of sun exposure on a wall, a sunny day in May or August should be taken as a measure to get a realistic, average value. We suggest the following classification:
1. 8-12 hours: full sun exposure, full sun
2. 5-8 hours: sunny
3. 2-5 hours: semi-shade
4. 0-2 hours: full shade to minimal sun exposure
It follows that even a southeast or a west wall can still be an "exposed" location.
An open area is always exposed to winds and is not particularly suited for climbing plants, because their evaporation becomes excessive in such environments. Much better for these plants are locations protected from the wind, ie areas protected from strong winds either by mounds, surrounding buildings or a grove. In the cities, most locations can be classified as "wind-protected."
Garden soil rich in humus is the optimal growing medium for climbing plants, and usually, the addition of a small amount of crumbly clay improves the soil further. However, a high groundwater table (say between 0.5m -1m) or a layer of clay below can lead to serious waterlogging.
Soils are also classified based on the roots' strength and ease to penetrate into it, ie deep soils (min. 75cm), medium depth soils (35-45cm) and shallow soils (only 15-25cm).
Most climbing plants originate from forests and forest edges, hence they appreciate a protected, moist soil environment which is subject to only minor variations in soil temperature. In the forest, the natural mulch or leaf litter ensures even soil temperatures, however in the case of façade greening projects, such an even microclimate must be established first. This is achieved with a 6-10cm deep layer of mulch either consisting of leaf litter, straw, grass clippings or similar, and which is replenished regularly.
Climbing plants tend to have a drying out effect on basements, which in earlier years was a commonly used technique. For example, a single grapevine has to absorb and evaporate 500 liters of water to produce 1kg of dry matter (which equates to approximately 10kg of fruit)! The widely branching surface roots will suck up all the rainwater first, while the deeper roots search for any lower lying soil water. If an area is drying up, the roots may die there, and other roots will grow towards the nearest available soil moisture.
However, such soil moisture is usually only sufficient for "emergencies" or during times of drought. Hence, due to the "oven" effect along walls, most climbing plants require regular watering!
If climbing plants are planted within the root zone of large shrubs or trees or within the root zone of plants with a huge uptake of water and nutrients, their development may be strongly impeded. A root barrier made from either foil, flag stones or large pavers, or using a large plant container with the bottom either perforated or knocked out, will solve such problems.