Ah, summer.
When the birds are chirping every morning, the kids are playing in the streets by afternoon, and indoor gardeners everywhere are still trying to keep their grow boxes cool long past the time that dusk eventually hits.
This means hunkering down with as much ventilation as possible, making sure that neither your lights or the torrential heat waves of summer raise the temperatures in your closet any higher than what they might suffer through outside. Indoor growers need to be especially careful, because unlike outdoor plants which use their deepened root systems to stay moderately cool throughout the hottest portions of the day, grow closets and tents retain almost all of the temperature they accumulate during the same hours, making for longer stretches spent in much less desirable conditions that can lead to water diseases, unstable pH, and a whole host of other problems we’ll discuss here.
Whether you use soil or hydroponics as the medium, keeping the interior of your closet as cool as possible should always be top priority, so here’s a guide on how to keep it below scorching for most important environment in your home.
While the obvious answer would be to simply not run your lights during the day and create more airflow between your closet and a couple windows in the house, unless you have some kind of central air source act as an intermediary between the two, often the only effect this strategy achieves is pushing more heat from the closet out into the living space, making everyone more uncomfortable in the process. A mistake that a lot of growers make is equating more power to lower temperatures, and then rigging a high-CFM fan to their tents that will actually produce more heat than they help to get rid of. Just because something isn’t physically in the grow space, doesn’t always mean their motors aren’t capable of heating up the surrounding area enough to negate the difference in between your closet and the rest of the house.
Keeping the plants cool should always be a vital concern for anyone who is worried about the their grow tent or closet, but more often than not the most damage actually occurs in the root system, rather than the leaves. Outdoor plants have the distinct advantages of being able to spread out their roots as deep and wide as they need to go, and are able to keep their roots cool underneath several feet of packed in soil no matter how hot the surface might be.
Hydroponics
With hydroponics this buffer is removed almost entirely, so the iciness levels of your water is just as important as what the thermometer at the top of your leaves reads. Most commonly industrial growers will buy a 1.5-2hp water chiller, depending on the size of their operation, to do the heavy lifting and keep their nutrient solutions at a manageable temperature without much input on their part. While this considered the smartest option, it can also be the most expensive one, so trying to keep reservoirs cool on the cheap isn’t always easy.
High level temperature control
If you don’t have an extra $400 to put into your setup there is a much cheaper choice available, although it also requires either you to be home all day, or have someone you know that can alternate “freezer-switching” shifts with you. About every 6 hours you can rotate a series of emptied two liter or one gallon bottles with a giant ice cube inside into your reservoir, and this will maintain the same effect that devices like ice probes would take care of on their own. Be careful though, because even one missed bottle could mean the difference between a patch of healthy, white roots in your system, or a grayish-brown moldy clump of nothing that was subjected to the dreaded fate of “root rot” when things got too hot.
Soil
Soil gardeners should always make sure to keep two items on board at all times; plenty of cold water to keep the top layer hydrated, and foliar spray that’s kept just above freezing between the fridge and freezer. This cold water will help to keep the plants hydrated and happy through the hottest of days, so you or someone in your home need to be around when temps really soar during the mid-to-late afternoon to give them a spritz or two of relief every couple of hours.
If you’re using a hydro setup don’t practice this too heavily, because as long as the source recirculating water is cold enough you should be able to keep the room at the same temperature, without much extra effort besides a fan placed in a strategic area near the res. Drop too low during early hours and your plants could go through “swing-shock”, or a state of non-production that plants will enter if temperatures vary too greatly in a short amount of time. These exercises are about maintaining a constant temperature in a certain place, not trying to mimic the same conditions that plants go through in an outdoor setting in our own spaces.
Another tried and true way to keep the room in controlled comfort is to employ the services of portable air conditioners, many of which contain methods of rigging air flow not unlike those in your average exhaust fan used to cool down the lights. Find the right fitting adjustments to connect with the intake and duct lines of your tent/box, and let automatic, self-timed operations keep your whole room cool with the nothing more than the press of a button.
Out of all the various methods we’ve covered here the last one is usually the most effective, and even if you’re growing in more of a ‘confined space’ than the hoses can fit into, just running the A/C in the general vicinity of a tent will allow you to monitor the ambient air and make decisions about what chilling methods are most appropriate according to your individual situation. If you have a break in your school schedule, use the off-time to put a roommate on bottle-duty, and if you’re a full time gardener who has a livelihood to depend on, maybe the small investment into a conditioner on wheels is worth the potential cost of decreased yields.
No matter what though, whenever the long, hot, humid days of the late-summer get you down all you have to do follow our guide, and you’ll be able to keep any plant cool while the rest of the world keeps heating up.