The term "microclimates" refers to close-proximity areas that vary in climate conditions. These variances are important to consider when deciding what, when and where to plant, impacting both growth and yield. Nearly every farm has microclimates of one sort or another (which, as we'll learn, can be altered or created using shade cloths).
From a macro perspective, microclimates are often noted when looking at urban and rural settings. In the urban setting, things like the asphalt, concrete and buildings absorb the energy of the sun, heating up and then releasing that heat back into the air. This results in higher urban temperatures than those in rural settings. In the rural settings, factors like proximity to water may cool down the air, resulting in more moderate climates at times, which is advantageous to areas with high summer temperatures. Water bodies like lakes, ponds, reservoirs and streams not only affect temperature levels, but also humidity levels (more water in the air).
The soil itself can cause climatic variances as well, mostly due to the amount of moisture absorbed and then evaporated back into the air. Clay soils retain more moisture than sandy soils and can affect the humidity and air temperatures of an area. Knowing the composition of your soil (sand, silt and clay) will provide a baseline for the effect it can have.
The slope of the land is another factor that can affect climates, with some areas receiving more sun radiation than others. As the days get shorter and the sun sits lower in the sky, shadows can lengthen and block out entire portions of beds. Therefore, it’s a good idea to place garden structures further apart during these times to allow for more direct sun exposure. Sometimes, the wind can whip up and around slopes, damaging plants. Areas like this should be treated like any high wind area; setting up wind-blocks, either naturally or synthetically, can help protect plants and infrastructure. Even though strong winds may not directly kill plants, they can stunt growth or otherwise set the plant back.
Microclimates can be effective in farming practices too. For example, in market farming (using a small amount of space intensely), plants are spaced with precision so that they quickly reach a point where the leaves touch, creating a canopy and shading the soil underneath, mitigating potential weed growth and protecting the soil. In this situation, the farmer is intentionally creating a natural microclimate within a single bed.
Another way to intentionally create and control a microclimate is by using shade cloths.
Shade cloths are vital for a successful growing season. They can easily be added to any structure to provide UV protection, keep your greenhouse cool, improve plant ventilation and reduce water usage. The main function of garden shade cloth is to protect the plants.
Shade cloths consist of either knitted or woven fabric made from polyethylene or polypropylene, which are synthetic polymer materials that naturally resist mildew and rot. Knitted polyethylene garden shade cloth is the most common variety used for covering agricultural structures because it has some give (will stretch a few degrees), is lightweight compared to woven fabrics and doesn’t fray along the edges. It is very durable and can be easily and quickly installed, especially when used in conjunction with cover hold-down clips, which firmly hold the cloth in place.
There are many different types of shade cloth for gardening, but they aren't distinguished by size and material alone. The amount of light they block, listed in percentages, is the most important factor to consider. For example, 30% shade cloth would allow for 70% light transmission. The percentage of shade cloth you need will be determined by the local climate of your farm location, direct sun exposure and the needs of your plants.
Use the infographic below to find the best shade cloths for your garden. Keep in mind that this is a general guide — we recommend that you seek advice from other experienced growers in your area who know your specific climate better than we do.
The most commonly used percentages of shade cloth for vegetables range from 30-50%. In northern climates, 30% shade cloth is the recommended density for extending the growing season into the summer for cool-loving crops like lettuce, spinach and Cole crops. In southern climates, 50% shade cloth is recommended for these same crops. In both northern and southern climates, 30% shade cloths are used to protect Solanaceae crops like tomatoes and peppers from sunscald.
The use of shade cloths and covers is an effective way for farmers to intentionally create artificial microclimates by blocking out a portion of the direct light that reaches their plants. Doing so can reduce the average temperature around plants by 10 degrees or more depending on the density of the shade.
It's important to pay close attention to your plants as they grow under garden shade cloth. If they aren’t receiving enough light, they may become leggy as they stretch and stress for ample light. One grower we talked with recently experienced this while growing salad greens under shade cloth during the heat of the summer. What they quickly learned was that when they kept the shade cloth on for an entire day, the greens became leggy and droopy. But, if they gave the greens full light until 3-4pm and only put on the shade cover after misting off the greens, they did just fine. Just like the farmer we spoke with, you will probably have to do some experimenting to figure out when and how to use your shade cloths to create the right microclimate for your plants and crops.
We're guessing you might have some other questions about how to find the right shade cloths for your garden. Listed below are the answers to some of the most common we hear at Bootstrap Farmer!
Shade cloths are great investments that can last up to 16 years when taken care of properly. Polyethylene and polypropylene shade cloth in particular can last a long time, since their edges are resistant to fraying and they are more resistant to mildew and rot than other traditional materials.
No — it only needs to cover the top above the hip board. If your shade cloths are too long, they will hang over your greenhouse or high tunnel's end walls and potentially get in the way of your door or vent fan.
Our shade cloths come with slight hems on the edges without grommets or clips. Our shade cloth clips close tightly over the material without tearing cloth, and they have a loop to make it easy to attach a rope or metal bolt snaps or eye snap connectors.
To figure out the size of garden shade cloth you need, measure the length and width of your structure. When measuring for a greenhouse, avoid going too long and overhanging on the end walls. The shade cloths only need to cover the top to the hip-board, as we mentioned before. The cloth can be attached with shade cloth clips, which have loops that can be used for tying off with a rope. Attach the clips on each corner of the cloth and at 3-foot intervals along the edges for secure attachment.