How Humidity Affects
Indoor Plant Growth

A dehumidifier should be used to keep humidity levels below 50% in the grow room and drying areas. They can be especially helpful in the drying areas!

Humidity plays a major role in plant growth, and it's effects are often underestimated or overlooked. To the right you will see the "tools of the trade" for controlling humidity...the dehumidifier and the humidifier.

A humidifier can be used in areas with very dry climates. Ideal humidity levels are 50%, +/-10%

Plants breathe through tiny openings on the undersides of their leaves called stomata. Plants can (and do) open and close their stomata under certain conditions, for example if heat becomes excessive and causes a plant to start loosing more water than it can take up, the plant will close it's stomata to slow down the water loss.

hydroponic gardening tip

The ideal humidity range for healthy plant growth is 50% humidity, plus or minus 10%.

Unfortunately, by closing the stomata and slowing evaporation the plant also has slowed down it's cooling mechanism. This causes heat to build up in the plant tissue, and in temperature too hot the plant actually cooks itself. It is important to understand the opening and closing of the stomata and how it, in turn, controls plant transpiration.

Air circulation in the garden is just as important as the air exhaust. This is usually accomplished with box fans and oscillating fans

Plant transpiration is how plants breath. Plants do not have lungs, however, so when molecules of gas and water vapor are released from the stomata they tend to just hang there in the absence of any breeze. That is why it is so important to have box fans or oscillating fans in a garden to circulate the air (in addition to exhaust fans). These fans are actually like the plant's lungs, and without them the plants would have no way of moving fresh CO2 molecules into contact with their plant tissue. The plants would slowly choke on their own transpired gasses and water vapor.

Learn more about garden fans here.

As water evaporates from the surfaces of leaves, the surface tension of the water molecules tend to pull the next water molecule along behind it, up through the plant's veins. Water is pulled up through the plant stem, which is pulled from the plant's roots. This creates a negative water pressure in the root zone and allows the roots to suck moisture up out of the root zone like a straw. The process of water absorbing into the plant through the roots is known as osmosis.

This is an affordable indoor/outdoor thermometer that also keeps track of humidity. It has functions built in to keep track of the highs and lows each day

Which brings me back to humidity. Water vapor is humidity. As a plant transpires, the humidity immediately surrounding the leaves will become saturated with water vapor. Now, the entire plant transpiration cycle is controlled by evaporation. When gasses surrounding a leaf become saturated with water vapor (100% humidity), there is no place for the next molecule of water vapor to evaporate to.

Box fans can be used in the grow room for additional air circulation

The end result is that water vapor is not evaporating, so water is not being drawn up from the root zone...and neither are any nutrients. If nutrients are not being taken up, than developing fruits are not getting the food they need to be healthy. This is exactly why high humidity will cause blossom end rot in fruiting tomatoes just like a Calcium deficiency. It is another reason why it is so important to keep box fans and oscillating fans in the garden area to keep the air circulating.

So, evaporation controls plant transpiration. High temperatures and low humidity therefore both cause fast transpiration. Fast transpiration means your plants will be taking up and using lots of water (and nutrients). This is fine, unless you were feeding your plants strong to begin with. Your plants can only handle so much fertilizer within a specific period of time.

A TDS meter (or EC meter) is a necessary piece of equipment, used to determine how strong the nutrient solution is before you feed it to your plants!

So if you now have warm temperatures, low humidity, and fast transpiration rates you may find your plants are using a little too much fertilizer a little too quickly. Leaf tip burn is usually a sign of this. Under these circumstances you can feed your plants with a weaker nutrient solution.

Or, if all other plant growth influencing factors are in their ideal ranges, you can try to maximize plant growth by adding CO2 (in which case you should experience heavy plant growth without showing any signs of stress or damage).

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Find 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 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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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!

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Soil Gardening

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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