Gardening is nothing more than mastering the environment around you. That is what each of us is attempting to do in our own gardens. There are some of us that are lucky enough to have our own greenhouses where we are the masters of the environment, or so we think. When we encounter problems in our ideal greenhouse, and we all have, we turn to publications such as this for solutions.
A greenhouse is a solar collector, solar collectors can be used to make hot water, and I find that to grow plants in this environment is difficult, but it can be done if you do the following things: spend large amounts of money for electricity to run the cooling fans that draw outside air into the greenhouse thru water cooled pads. This is called evaporative cooling, and it does not work efficiently when the outside humidity is 50% or higher. We pray for cloudy days because we know from experience those cloudy days outside equal cooler days inside.
We have also found out that as the sun heads south on its path, we are thankful for the lower intensities of sunlight and we call this fall, and the plants need it. Since last spring, they have been operating non stop. Light levels increase, heat levels increase, water consumption is increased and when the light and heat levels are at maximum in the summertime, your plants or crops are stressed to the max.
The next step we need to take is the one that comes about when you ask the question of: How much of the incoming sunlight do the plants really need for proper growth? The answer may surprise many of you. Plants can only process 1 ½ to 2 % of the sunlight they receive for photosynthesis.
In any gardening endeavor, while we are attempting to “Master the Environment” we find that in growing tomatoes, we need a temperature of 45 degrees to set blooms, after bloom set, we need a percentage of shade that will protect against high soil temperatures after that. Mulch is excellent for this and is the very first step, or adjustment, for climate modification. The most successful adjustments are ones that maintain high light intensities, but without direct sun.
When used properly shade cloth can help solve the problem by creating a microclimate underneath the shade cloth. All of us have been in Nursery’s where the newly arrived plants are placed underneath the shade cloth covering, and in effect, this is one way to harden them off. I simply take this low cost, low tech procedure a few steps farther by expanding up to 12 feet above the ground, coverings as much space as Mrs. Shade will allow me have. I also take the shade cloth down to the ground, creating a more complete microclimate that does not have any excessive wind. Shade cloth makes an excellent wind screen. Melon growers in Israel and the tomato growers in Spain grow crops with reduced light intensities and lower ground temperatures with this method. By using it they have vastly increased crop yield with a 35% water reduction. At the same time, since they are in screen rooms, their pesticide use has been reduced as well. Take the stress out of the plant by sunlight intensity reduction and you naturally get a stronger plant. Stress a cherry tomato plant and watch the bugs zero in on it.
Shade Cloth is manufactured and used world wide in various applications. One that everyone is aware of is its use as privacy or wind screens around tennis courts. There are a number of restaurants that have installed shade cloth to create outdoor environments for dinning. For milk production, shade cloth is used from the calving area to the feed area to the pasture area. Cow’s in this microclimate produce 21% more milk.
Sunlight and its impact on earth can be measured easily by its impact on our daily lives and the environment that it creates with its attendant heat. It is this heat that stresses every living thing and well as any object that it strikes. Go back to the “It’s Not Rocket Science” and actually use the information that the rocket scientists have gathered. They have instruments in space that measure the incoming energy from the sun. NASA uses the figure of 1356 watts per square meter. That is a whole lot of power, and if all of that impacted the earth’s surface, life would not exist.
How is it That we are Here?
The atmospheric ozone is the starting point, as it screens out, or filters out, most of the ultra-violet spectrum. As ozone depletion occurs, skin cancer rates go up. In total, the atmosphere reflects 30% of the incoming radiant energy, and it absorbs 28% into clouds and water vapor. The remaining 42% is what you and I and the plants need to deal with. It is this 42% that creates the heat/loads to our greenhouses, our solar collectors, our homes and are cars. When we total the above percentages, we find that 58% of the input energy is stopped or absorbed by the atmosphere, so the atmosphere is acting and functioning in the same manner as shade cloth.
Shade Cloth, by intercepting 75% of sunlight input, turns it into heat energy by absorption. This raises the temperature of the shade cloth, (Shade cloth is a solar collector), this temperature is hotter than the air above and below the shade cloth and there is only one direction that nature allows for that heat energy to flow: up. And as it flows up, it draws cool air from below. The shade cloth by evaporative cooling is performing the same function as a tree, and we all know the cooling effect of a large tree on a hot day. Trees and the microclimates they create are fun places to garden. Shade cloth structures are even more fun because now you are the master of your environment. You have controlled the sunlight input, and it’s not rocket science.
Think about that sterilized greenhouse that we have cooled down with lots of electricity and money. Move all of your plants back in and you are mastering your environment again. Its July, it’s hot, and a car runs into the power pole down the block, and now you do not have any power to your greenhouse for cooling. As you stand there helpless, and frustrated, you watch your crop yield wither and die within 4 hours.
The point is: If you cover your greenhouse with 63% shade cloth, 12 inches above the roof, 12 inches from the wall, all the way to the ground, a tremendous amount of heat load is dissipated by the cloth, it never gets into your greenhouse, and now dollars are going back into you pocket by reduced energy cost. Talk about going green, talk about lowering your carbon footprint, shade cloth does it. You put sunscreen on your body; why not use sunscreen for your plants?
Shade Cloth Cost-- Length of Life—Colors—Shade Densities
Raw material comes in widths from 6 to 10 feet wide. It can be sewn with reinforced taped edges and grommets that can be installed every 18 inches. The polypropylene threads can be woven in weaves that allow specific percentages from 30% shade to 100% shade.
Standard off the shelf shade cloth stock percentages are 30%, 55%, 63%, 73%, 80% and 90%. Standard off the shelf colors are Black, Green, Red, and sometime soon, white. Cost is generally about $.45 per square foot for raw stock and $.60 per square foot for taped edges and grommets.
Life is a shade better under a tree or shade cloth.
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