Climbing plants, roses, grapevines and espalier fruit have certain location requirements (that is, where they can grow). Learn here about the determining factors for successful façade greenings in Central Europe. Based on this information you can assess the position and aspect of your garden, select the most suitable climbing plants or, if necessary, adjust some of these factors so that a preferred plant species can gain a foothold and even thrive in a less than optimal location.
Plants need light to develop flower buds. But equally so, they need the heat radiated from the sun: full sun on a brick wall allows a microclimate to develop which will produce an abundance of flowers and fruit, the like of which you will not get in a freestanding 'open' position. The wall stores the heat and radiates it during the evening hours, which further promotes the ripening of the fruit. On wooden houses and those with external insulation, this "oven" effect is also present, though to a considerably less degree
Unfortunately, a lot of heat also increases the evaporation rate and thus water consumption. Some plant species become very susceptible to fungal attack under heat stress.
In order to determine 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
Even a southeast or a west wall can therefore be an "exposed" location.
An open area is always exposed to winds and is not particularly suited for climbing plants; in such environments they lose a lot of water through evaporation. Much better for these plants are locations where a windbreak is created by elevations (mounds), surrounding buildings, or shrubs/groves. Urban locations can almost always 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, i.e- 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 6-10 cm deep layer of mulch, consisting of either leaf litter, straw, grass clippings, or similar, and which is replenished regularly.
Climbing plants tend to have a drying effect on foundation walls, which in earlier times was a commonly used technique for the greening of buildings. For example, a single grapevine has to absorb and evaporate 500 liters of water to produce 1kg of dry matter (which equates to about 2 kg of wood or 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 out, the roots will atrophy there, and other roots will grow towards the nearest available moisture source.
However, such natural soil moisture and also the deeper groundwater are usually only sufficient as an "emergency supply" 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 in the vicinity of plants that consume large amounts of water and nutrients, their development may be considerably thwarted. A root barrier-- made from either foil, stone slabs, large pavers, or using a large plant container with the bottom either perforated or knocked out-- will solve such problems. Even smaller undergrowth plants can hinder the climbing plant in the first growth phase.