NOTES ON THE MAINTENANCE OF VERTICAL GARDENS
October 15, 2020
While the maintenance of vertical gardens somewhat depends on which system is used, the general requirements are similar. Before looking at typical maintenance topics like trimming, lets first make sure the set up of the vertical garden is done properly. A correct setup is the first step to minimize maintenance.
The irrigation system is the heart of a vertical garden
Unlike a wall covered in ivy or other climber, plants on living walls and vertical gardens do not have any contact with the ground, leaving them dependent on an irrigation system for supply of water and nutrients. Some systems have more soil (or other substrate) that stores water than others, but regardless of system a water cut is the biggest threat to the survival of plants. However water cuts are luckily very rare, and can be avoided with wifi connected irrigation systems or just regular visual inspections of the garden.
Fertilizing the vertical garden is critical in the long-term
It may be tempting to avoid the costs of installing an irrigation system without fertilizer pump, but in the long run plants will suffer from that. At the time of installing the vertical garden, the soil that plants arrive in from nurseries generally contain fertilizer. So plants can initially grow well for several months without adding fertilizer. But over time the growth and health of plants will suffer and so will the overall appearance of the green wall.
Having sufficient light levels
Outdoor vertical gardens generally have sufficient natural light, and while selecting plants it is crucial to evaluate light levels and sun exposure to choose suitable species. As for indoor projects it is generally necessary with additional lighting. During the last years plant lighting for vertical gardens has moved from metal halides to LED. Few plants will survive light levels lower than 1000 lux and most need a bit more to show proper growth.
Plant selection for vertical growing locations
In addition to assessing the light levels on site, an outdoor living wall needs plants suited for the local climate. Native plants are often a safe choice as they are adapted to local conditions. However the specific growing conditions on a vertical garden sometimes make it quite limiting to use only native species. Plants that in nature grow on vertical surfaces such as tree trunks (epiphytes) or rock faces (lithophytes) are most suited. These plants often have roots that grow attached to the wall (to keep them stable through wind and rain) and also grow in a shape adapted to such exposed locations.
In general we like to work with a diverse plant selection. Not only do we believe it makes the vertical garden more beautiful and interesting, but it can also make it more resistant to pests as these most often infest a specific species. So with more plant variety, there is improved resistance to pests.
Using plant design to minimize maintenance
From a maintenance perspective the layout of plants ideally allows each plant to develop to it’s full potential without any impact on adjacent plants. In reality that is difficult if using a variety of plant species, but it can still be a guiding principle. Some examples: vigorously growing plants can be kept close to a wall edge where they are easier to control, large plants should not be placed so they block light sources as they mature, cascading plants are better planted in a vertical pattern to avoid them covering plants below.
Time to trim
Now that the vertical garden system has been set up in the best way possible and plants are healthy and thriving, it’s time to trim. In general it is sufficient to trim plants 1-2 times per year. The purpose of trimming is to maintain a more compact appearance and allow all plants sufficient light exposure. If let to grow uncontrolled some plants will grow on top of adjacent plants and block their light exposure, hindering them to survive. Other plants will grow in thick layers which if never trimmed will create a lot of dry plant matter behind the outer layer of fresh leaves. That may not be a problem but often look bad with time.
Larger accent plants also tend to block light for adjacent plants. They can be cut back keeping only a few leaves to remain an interesting feature on the wall.
Pest control
Healthy plants are more resistant to pests, so having the living wall system properly dialed as discussed above will make the garden more resistant to pests. Yet it is in our experience quite common that insect pests appear. They may be introduced already with the nursery plants or come from outside.
An exterior plant wall attracts a variety of insects just like any garden. Some are beneficial (e.g. predator insects that eat pests) others cause damages. Overall this variety of insects seems to achieve a better balance and it is more rare that treatments are required on outside projects compared to indoor.
In indoor settings there is no natural presence of beneficial predator insects, but these can be introduced as a treatment. Part of the maintenance check-ups is inspecting the plants in order to see if any treatment is required. The earlier pests are discovered the easier to apply a treatment.
