Maintenance of Vertical Greening Systems
1. Introduction
1.5. The effect of seasonal variation on the maintenance of vertical greening systems
The effects of seasonal fluctuations are more strongly pronounced for exterior living walls than for their interior counterparts. Seasonal changes affect the ambient temperature, solar radiation, humidity, drought, frost and biological growth of plants. As a result, the growth of the plants accelerates or slows down, the level of evapotranspiration changes, and the need for nutrients and the use of different nutrients at different stages of growth can fluctuate accordingly.
External living walls
The physiological conditions in exterior green walls that can adapt to the need of the plants are regulated in accordance with seasonal influences:
Spring growth
Moderate watering is required so that the substrate is mildly moist, using appropriate phosphorous fertilisers to improve root development, fertilising via the roots and leaves.
Summer growth
Heavy watering is required due to the increased levels of evapotranspiration. The fertiliser should contain a high dose of potassium, and control of pests and diseases should be increased, especially during wet periods.
Autumn growth
Moderate watering is required, using fertilisers with a high dose of potassium and humic acids in order aid the plant’s preparations for hibernation.
Winter hibernation
There is a threat of winter drought in February when the water in the substrate may be frozen and the level of sun radiation is already high. It is vital to water and spray evergreen plants regularly during sunny weather using warm water. Since the plants do not produce biomass during this phase, fertigation is not necessary. Deciduous perennials and small shrubs should be watered occasionally during good weather, which dries out the substrate in living walls.
Internal living walls
In interior living walls, the impact of the changing seasons is reflected in the reduction of natural lighting and humidity due to heating. Cold draughts might occur due to the close proximity of doors, which adversely affect the growth of indoor plants. Therefore, the level of watering and fertigation used for interior walls follows a similar process to that used for exterior walls.
Spring
The fertilisers need to contain more nitrogen in order to encourage plant growth. Only moderate watering is required; better too dry than too wet. Lighting needs to be between 800–1200 lux for at least 12 hours a day.
Summer
The fertilisers used need to contain appropriate proportions of nitrogen and potassium in order to achieve more compact growth. Calcium and magnesium need to be added when using soft water for irrigating. The level of watering is the same as for spring. Lighting needs to be between 800–1200 lux for at least 12 hours a day.
Autumn
The fertilisers need to contain a high level of potassium, bio-activators and microelements. The level of irrigation should be moderate; better dry than wet. Lighting needs to be between 1200–1400 lux for at least 12–14 hours a day.
Winter