How do plants use water?
Plants need water to complete photosynthesis. Photosynthesis is the process in which plants make food from water and light. Water enters through the roots of the plant, travels up to the leaves and is exchanged for carbon dioxide when light hitting the leaves evaporates the water. This exchange provides food and energy for the plant. The amount of water a plant needs depends on the type of plant, the amount of light, and plant maturity. Plants in a hot sunny environment will require more water due to the increased rate of evaporation occurring at the leaves. Additionally, the water also needs to be of good quality. Water carries minerals, both good and bad, to plants. It is important to make sure the water source has a neutral pH level and isn't too high in contaminants such as sulfur, chlorine, or iron.
When watering goes wrong
Over watering a plant leads to the plant "drowning". The roots become so saturated that plants are unable to take in oxygen.. The water pressure in the leaves will increase and cause the plant to wilt since the plant will not be able to support the extra water weight. The wilting will give off the appearance of under watering but the soil will be moist. Leaves of the plant will also turn brown or yellow as the plant suffocates. It is not uncommon to see both young and mature leaves falling from an over watered plant. Over watered plants will continue to produce new leaves and even bloom.
Under watering a plant leads to the plant "starving". Since water is need to make food and energy the plant will eventually die of hunger. The physical changes will appear similar to over watering but with dry soil and no new leave production. The plant will wilt due to lack of energy to hold itself up, leaves will turn colors and fall off as well.
“Part 2: How are living green walls watered?”
One of the most basic considerations for a green wall is whether it will be manually watered or automatically watered. Larger scale living wall projects will require automatic watering, but for small and medium sized walls manual watering is also an option.
Manual watering is when someone adds water to the green wall by hand. Water can be added using a watering can, a portable water tank machine or a temporary hose connection. This is an economical option because it eliminated the upfront cost for plumbing, drain lines and electricity. Manual watering is only used for small and medium sized living walls because the volume of water needed for larger walls makes manual watering impractical. Additionally, to allow for manual watering, a green wall needs to be easily accessible. Any green walls installed in hard to reach locations are not good candidates for manual watering.
Automated watering is when the green wall is connected to the building’s plumbing system and watered without any human intervention. The flow of water is regulated by a computerized control box. The control box utilizes either moisture sensors or a timer system to only add water to the green wall when it is needed. These programmable systems provide for precise control of watering frequency and volume. Additionally, some control boxes also have the ability to inject fertilizer into the green wall’s water supply. An automatic watering system is more costly to install, but it usually lowers the maintenance cost and it removes the possibility for human error. Automatic watering is optional for small and medium sized green walls, but it is a requirement for larger or complex green walls.
The water irrigation system is a vitally important component of the living green wall. When designing a green wall system it is very important to carefully consider the best irrigation option for your specific location.
Many people like to water manually as it has lower upfront costs and allows the plant maintenance person to see the fruits of their labor. Automatic watering proves to be helpful for people who like to set it and forget it. Automatic irrigation systems have higher upfront cost but lower ongoing maintenance cost. The simplicity in setting the system and forgetting it allows the green wall to constantly receive water and continue to thrive.
No matter if you choose manual watering or automatic irrigation, you must ensure that the living wall gets the proper amount of water. Both over-watering and under-watering a living wall can cause big problems for the plants. The water amount can change over the life of the wall as plants grow and need more water and it can also fluctuate during a year if the plants get more or less light at different times. Be sure to know the total water capacity of the living wall, the estimated water use per week and keep a close eye on the soil moisture level.
Water: The Essence of Life & Living Green Walls - Part 3
Water is essential to all life. It keeps us hydrated and keeps all of our vital organs functioning. You cannot live more than a few days without water. In much the same way, water is also essential for plants.
Water is therefore an important consideration for any living green wall project. It is important to know how plants use water, how to spot plants having a water-related issue, and how different types of green walls can be irrigated. In this three-part blog post, we will be examining the topic of water and how it relates to living green walls.
“Part 3: Where does the water come from?”
Nearly all living walls use the building’s standard water supply, but a few living walls have been designed to use rainwater, grey-water or storm-water. These recycled water systems are great in theory, but in practice the drawbacks usually tend to outweigh the benefits. Recycled water must be filtered and pH balanced before it can be fed to the plants. The micro-contaminants in recycled water and the altered pH levels can have very harmful effects on the plants in a living wall. The required filtration and pH balancing systems are not cheap. In addition, you are still required to have a standard water connection anyway since the supply of recycled water is not guaranteed. The secondary water line is needed as a fail-safe in the event of a drought or reduced gray water supply (i.e. weekends & holidays). Being green and recycling water is fantastic, but unfortunately green walls are not well suited for utilizing recycled water.
Drippers or Wickers
Most living walls use a system of automated irrigation lines with tiny emitters that drip water on/into the soil or growing medium. A smaller number of systems use synthetic cloth wicking systems that utilize natural capillary action to draw water up to the plant roots. Capillary wicks are simple and reliable, but because they deliver a constant supply of water you cannot easily adjust the watering for different plant needs. Drip emitter systems can be tailor made with different watering zones for different plants, but they are more labor intensive to install and there is always a risk of the tiny emitters becoming clogged.
To Recirculate Or Not To Recirculate, That Is The Question
Some living wall systems utilize a recirculating system to recycle and reuse excess water. In a recirculating irrigation system, there is a supply water tank at the bottom of the green wall that is filled from the building’s water supply. The tank water is then pumped to the vegetation in the living wall and the excess water drains down to a catch basin at the bottom of the wall and then back into the water supply tank. The system recirculated the water through the wall many times per day. The goal of these recirculating systems is to increase water efficiency and not waste as much water.
Recirculating systems are great, but they do have their drawbacks. One potential issue is with the excess water collected in the catch basin. This water can become contaminated from running through the living wall and recirculating that water can spread the contamination to the entire green wall. A single plant with a soil-borne disease can become a big problem. Another potential issue is the energy efficiency of the pumping system. Recycling the water seems like a sustainable water conservation solution, but the cost may be counterbalanced by the increased electrical demands of the pumping system.
Nutrition
Plant nutrition, such as water soluble or liquid fertilizer, can be delivered through the irrigation system. In a recirculating system, salt-free liquid fertilizer can be added to the water storage tank. Direct irrigation systems may incorporate a nutrition injection system to draw liquid fertilizer from a container or storage tank into the irrigation system during the watering cycle. Nutrition can also be delivered manually, depending on the type of wall.
The effectiveness and efficiency of a watering system is based on how well the water is directed to plant roots with minimal excess waste water. You don’t want to waste water, but you also don’t want to spend a ton of money or energy trying to save a small amount of water. The water use has to be balanced with the overall energy use of the system. The right answer will be different for different projects and different geographies. There are always inherent risks to using water indoors, so it is important to consider all worst-case scenarios and related risk mitigation strategies.
You need to be a member of Moondance to add comments!
Replies
WATER IS SO IMPORTANT TO OUR EARTH, IT IS IMPORTANT TO OUR LIFE IN SO MANY WAYS. THANKS BRIDGET, GREAT POST.
Interesting, thanks Bridget!