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Are your tomatoes plants wilting?
Have your greens gone to seed?
Hot summer days call for drastic heat mitigation measures when it comes to greenhouse gardening. Lucky for us mountain dwellers, we only have to deal with the dog days of summer for a few weeks out of the year. The rest of the time, we praise our greenhouses for extending the season through both the early and late frosts.
As a high-altitude greenhouse gardener, you may have overlooked the need to cool things down due to extreme heat. But, when outdoor temperatures reach 80° F or above, indoor greenhouse temperatures can climb well over 100° F. This can cause even heat-tolerant veggies, like tomatoes and peppers, to drop their flowers or produce sterile pollen.
With a few simple measures, however, you can avoid this problem, as well as others like uneven ripening and sun-scalded fruit.
1- Location. Location. Location. Before you even start the growing process, choose a place for your greenhouse that already receives natural shade. Existing trees and shrubbery, your house, or an outbuilding can all act as a sunblock during the heat of the day. If your yard gets exposure to direct sun, you may want to situate your growing space in the northeast corner of your property, rather than the southwest.
2- Remember, heat rises. Ceiling vents are one of the most efficient ways to cool your greenhouse down fast. Install crack vents that can be opened with a pole or heat-activated vents that open automatically when the mercury inside rises.
3- Enlist the help of shade cloth. Woven cotton or polyester shade blocks are highly effective at regulating greenhouse temperatures. With a looser fabric weave, you can deliver full-time sun at just the right amount to produce a fruitful harvest without overheating your plants. A tightly-woven cloth, however, can dampen your yield unless you situate it properly or raise and lower it throughout the day like a curtain.
4- Create flow-through venting. New gardeners should opt for a greenhouse that has a door on one end and either another door, a window, or a large vent on the opposite end. A flow-through breeze acts similarly to the wind activity your plants would experience outside in their regular habitat. Plus a slight rustle helps acts as a pollinator.
5- Turn on the fan. The hottest days are usually wind-free, and that’s when it’s time to break out the fans. Fans placed near doors on the floor can bring in cool air, while fans placed in the rafters can blow hot air out of ceiling vents. Just be sure to turn off your fans at night when the mountain temperatures plummet.
6- Damp it down. An ingenious, and sometimes overlooked, way to cool off your greenhouse is by raising the inside humidity. Now, that doesn’t mean overwatering. It simply involves the act of hosing down the structures inside your greenhouse. Hose off the walkway, the planter boxes, and other hard surfaces once in the morning and once at night.
Like with anything gardening, it takes diligence to keep extreme heat from hurting your cherished plants. But, with a keen greenhouse design and a few mid-summer habits, you can prevent Mother Nature’s wrath when she turns up the heat.
