Sep 14, How Plant Growth is Affected by Temperature

high temperature leaf burns

The ideal temperature range for plant growth without CO2 supplementation is 70-75 degrees. Temperature is probably the factor that causes the most problems in an indoor garden. When the temperature in a garden climbs higher than 85 degrees, plant growth damage can happen quickly. As far as temperature is concerned, you have the following factors working against you when you begin to improve your garden area…

the more watts you add to an area
the more enclosed you make the area
the less adequate your exhaust system is
the smaller the area is
The worse your heat problems get!

The general idea for controlling heat is to exhaust the hottest air out of the area and, at the same time, introduce cool, fresh air in to replace the exhausted air. This source of cool air is critical. Plant growth slows in hot, humid conditions, and your ability to control the temperature in the garden area is only as good as your source of cool, fresh air.

Indoor/Outdoor Garden Thermometer The most important thing is that you know the temperature in the hot spot of your garden area. This is usually directly under the center of your grow light, at the tops of your plants. The plant growth in this area is the most vulnerable to damage from high temperatures in the garden. For this, every indoor gardener should have an indoor/outdoor thermometer (the kind with a cord and remote probe).

Here are four strategies you can use to help reduce the temperatures in the plant growth zone of your indoor garden area…

1. Open the grow area to allow air circulation with a larger volume of air
2. Keep the grow light exhaust and the garden area exhaust as two separate systems
3. Increase the size and number of exhauste fans for the area
4. Add air conditioning

Larger volumes of air act as a buffer against temperature increases. A garden grown in a small closet with a 400 watt light, an oscillating fan for circulation, and no exhaust fan will have a problem with high temperatures.

On the other hand, the same 400 watt light placed in the corner of a large bedroom, with the same oscillating fan, may operate without any problems of high temperature (especially in winter months).

Let’s say you had a 600 watt light in a high quality reflector that had nice big 6 inch vent holes thru it and glass in the bottom. Let’s say you placed this light in a completely enclosed 4 foot square box. You could duct air in from a window, through the enclosed light, and exhaust it back out the same window.

With the light efficiently cooled, far less heat ends up in the grow box and the temperature inside rises much more slowly. This means you can run an exhaust fan that kicks on and off as it is needed. Now you can run an exhaust out from the grow box and run it on a thermostat.

Once you no longer have to exhaust continuously to control the heat, you will be in a much better position to use carbon dioxide to try to maximize your plant growth.

The exhaust from a grow box should always be somewhere near the top of the box (because heat rises). This makes it only natural to make the fresh air intakes lower to the ground, around the bottom of the grow box or grow chamber.

Again, your ability to control the temperature will only as good as your source of cool, fresh replacement air.

If the air temp outside is 70 degrees, than you should be able to get the temperature in your garden area down to 75 degrees….if your exhaust fans are good enough, that is. Box fans and oscillating fans are needed in the garden to circulate the air and to help all the plant growth breathe properly, but as exhaust fans they suck! They do not move nearly enough air.

There are two types of fans used (efficiently) to exhaust indoor garden areas. They are…

squirrel cage and centrifugal fans

The main difference is that centrifugal fans are quieter, more powerful, and more efficient than squirrel cage fans. They are also more expensive. However, if you plan on using a carbon filter, have to get a centrifugal fan….squirrel cage fans just don’t have what it takes when it comes to pulling air in volume through a carbon filter.

As a general rule, the CFM rating of your exhaust fan should be able to exhaust the square foot volume of your garden area in 5 minutes or less to be ok. Practical experience has shown me it usually takes even more than that to control temperatures in a garden, especially when no air conditioning is used.

Get more information on garden exhaust fans here.

Air conditioning is the final solution when it comes to controlling indoor garden temperatures. With AC, you are always guaranteed a quality source of fresh, adjustable cold air. Gardeners that use air conditioning do not exhaust their gardens continuously.

The strategy for using air conditioning is usually to run the lights on a separate exhaust system from the garden area. Whenever the temperature gets too warm, the garden exhaust fan kicks on at one end of the area while the air conditioner operating at the other end acts as the fresh air intake.

Gardens using carbon dioxide to maximize plant growth would then release CO2 once the exhaust fan(s) shut off.

It is generally accepted that gardens can be ran at higher temperatures when using CO2 supplementation to maximize plant growth. While this is true, it is important to understand that this is only the case when all other growth influencing factors are kept in their ideal ranges. The ideal temperature range for the indoor garden is 70-75 degrees. With the addition of CO2 you can run your garden up to 10 degrees warmer without seeing any negative effects.

The other place where temperature is a concern is in your nutrient reservoir. In the plant growth and oxygen page, I describe how the uptake of nutrients (in the root zone) only occurs in the presence of oxygen. The fact is, water looses it’s ability to hold dissolved oxygen as it warms up.

If the nutrient solution gets too warm, your plants will not be able to take up any nutrients (and therefor they will not grow). Worse yet, the nutrient solution will begin to favor a number of pathogenic micro-organisms at a warmer temperature….nasty things like fusarium and pythium. The ideal temperature for your nutrient solution is 65 to 70*F. If your garden is in the basement, keeping the nutrient reservoir on the concrete floor will usually keep it at an ideal temperature.

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Check out other Hydroponic Gardening Tips and Tricks

Dirt Cheap organic and hydroponic gardening suppliesFind out the cheapest and easiest ways to garden productively in this article.

Hi everyone, Jason from Jason’s Indoor Guide here. When I got started with hydroponic gardening more than 20 years ago, my first garden used rockwool cubes and B.C. Nutrients….and I remember thinking to myself yeah, sure, there may be a lot of advantages to gardening with hydroponics, for example there are very few pest problems, therefore very little pest control, no weeding, no plowing or tilling the soil, no soil testing or having to add things into the garden soil, no watering the garden….but for someone who just wants to grow their own vegetables and have more control over their food supply and the quality of the food that they eat, the cost of constantly having to buy grow media and hydroponic nutrients makes this an expensive hobby for most people.

I suppose when you take into consideration how much money you save NOT having to buy food at the grocery store, it is surely cheaper to grow your own food hydroponically even with the cost of high quality nutrients. Nevertheless, I didn’t have a whole lot of money to work with and I needed to make my efforts as affordable and effective as possible….and in the last 20 years I HAVE learned a thing or two!

As you browse through Jason’s Indoor Guide, you will notice all of the systems that I use personally are homemade systems. As I got 3 or 4 years of experience under my belt, I quickly adopted a preference to standing water systems and systems that use expanded clay pellets or lava rock, because the media is re-usable and it eliminates a huge operating expense. So once a hydroponic system is built, garden maintenance is minimal- check and adjust the nutrient solution daily, and to change it completely every 2 weeks….and the biggest operating cost is the hydroponic nutrients. (and the electric bill, lol).

And, regarding the cost of the nutrients….I experimented for about 3 years with making different compost teas and nutrient teas, but there is still a lot of expense $$$ associated with making high quality nutrient teas….like kelp meal, liquid seaweed, rock dust, bat guano, un-sulfured molasses, worm castings. You can eliminate a lot of this expense by becoming an expert at making high-quality colloidal humus compost, and use your properly made compost as the basis of your hydroponic nutrient solution.

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Unfortunately, I have been gardening for over 20 years and I have only just recently mastered this difficult skill….and even then, only because I happened to find a very easy to follow, high quality technique and decided to follow the instructions to the letter. I produced more high quality compost in just one week than I was able to use in a whole year! I highly recommend it. It is one of the top 3 things you can do to increase the productivity of your food production efforts, while at the same time decreasing the amount of effort required to grow all of your own food, and decreasing the total cost of operating your food production system.

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One final solution to eliminate the cost of your hydroponic nutrients: Imagine a hydroponic system that does not require you to buy any nutrients, does not require you to make your own compost, and does not require you to brew your own nutrient tea. Seriously! No cost and no effort as far as providing nutrients to your plants is concerned. Plus, at the end of the gardening cycle, you harvest all of your garden vegetables, PLUS YOU HARVEST FISH from the system!

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This solution is aquaponics. If you are serious about producing all of your own food and being self-sufficient, this is the ultimate solution for reducing expenses (as much as possible), reducing the total amount of work required, and maximizing the productivity of your gardening efforts. I have been gardening for over 20 years, and it is the perfect food production solution in my opinion.

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Besides mastering how to make high quality compost, learning aquaponics is one of the top 3 things you can do to increase your garden productivity, reduce your total costs, and reduce your total work. The product that I learned from is called Aquaponics4you. With all of my hydroponic gardening experience, the first time I came across the Aquaponics4you product I knew immediately that it was something very special! Place an aquaponics system outdoors and use the sun instead of grow lights, and you have reduced every garden expense to nearly ZERO!

This is where my advice ends for people growing in water. But some of you out there are in love with soil gardening and organic gardening, and rightly so! It’s a pro-human activity. It is pro-conservation. It is pro-life. It nurtures and promotes life at all levels, from the micro-organisms to beneficial insects, to healthy humans. It’s natural. it’s spiritual. Gardening is written deeply into our DNA, like how you feel watching a bonfire or sitting by the ocean or next to a river.

My friend John at Food4Wealth has more than 20 years experience organic gardening, so he reminds me a lot of myself. He knows organic gardening like I know hydroponic gardening, and over the years he has learned just about every trick there is to organic gardening. He knows what makes the plants grow, and he knows how to do it with as little effort as humanly possible. His garden never needs digging, naturally repels pests, has no weeds, always produces more than his family is able to eat, produces vegetables everyday all year round, and….only requires 8 HOURS of light, easy effort PER YEAR!

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Years and years of experience and results can’t be argued with….the Food4Wealth gardening strategy is one of the top 3 things you can do to increase your productivity, reduce your total costs, and reduce your total work….specifically for organic gardeners who love soil gardening. THIS is the most efficient and productive way to do organic gardening, period! And combined with the ability to make a years’ worth of colloidal humus compost in just one week (see World’s Best Compost), this overall organic soil gardening strategy is just unstoppable- foolproof, low cost, and low effort!

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