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Question on Root Zone Temps.

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#1 Buddha



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Posted 22 July 2009 - 11:24 AM

My questions are:

1)What is the best and worse temperature for the roots?

2)What happens if you fall outside this best temerature?

3)What are some of the signs you are outside this temperature?

I have looked pretty much everywhere for an answer to these questions. Done a advanced search here in the threads, looked through all my own books, and Googled...Nothing.

I am posting these questions because I feel it is a important peice of information everyone should have. I have a large selection of material in my library but have been unsucsessful in finding what I need and most likely what others could use also. This artical Below from "Ed Rosenthal's Grow Tips" is the best I could find. Please help us out expert gardeners.

Ed Rosenthal's Grow Tips

Maintaining Optimum Grow Room Temperature
Marijuana plants are very hardy and survive over a wide range of temperatures. They can withstand extremely hot weather - up to 120 degrees - as long as they have adequate supplies of water. Cannabis seedlings regularly survive light frost at the beginning of the season.

Both excessively high and low temperatures can slow marijuana's rate of metabolism and growth. The plants function best in moderate temperatures - between 60 and 85 degrees. As more light is made available, the ideal temperature for normal plant growth increases. In high temperature and moderate light conditions, the plant's stems elongate. Strong light and low temperature conditions will decrease stem elongation. During periods of low light, sem elongation can be decreased by lowering the temperature.

Temperatures below 50 degrees slow growth in most varieties of marijuana. When the temperature drops below 40 degrees, the plants may experience some damage and require about 24 hours to resume growth. Low nighttime temperatures may delay or prevent bud maturation. Some equatorial varieties stop growth after a few 40 degree nights.

A sunny room or one illuminated by high wattage lamps heats up rapidly. During the winter, the heat produced may keep the room comfortable. However, the room may get too warm during the summer. Heat rises, so that room temperature is best measured at the plants' height. A room with a 10 foot ceiling may feel uncomfortably warm at head level but be fine for plants 2 feet tall.

If the room has a vent or window, an exhaust fan can be used to cool it. Totally enclosed spaces can be cooled using a water conditioner which cools the air by evaporating water. If the room is lit entirely by lamps, the day/night cycle can be reversed so that heat is generated at night, when it is cooler out.

Marijuana is low-temperature tolerant. Outdoors, seedlings sometimes pierce snow cover, and older plants can withstand short, light frosts. Statistically, more males develop in cold temperatures. Low temperatures, however, slow down the rate of plant metabolism. Cold floors can lower the temperature in containers, thereby lowering root temperature and slowing germination and plant growth. Ideally, the medium temperature should be 70 degrees.

There are several ways to warm the medium. The floor can be insulated using a thin sheet of styrofoam, foam rubber, wood or newspaper. The best way to insulate a container from a cold floor is to raise the container so that there is an air space between it and the floor. Overhead fans, which circulate the warm air downward from the top of the room also warm the medium.

When the plants' roots are kept warm, the rest of the plant can be cooler without danger. Heat cables or heat mats, which use small amounts of electricity, can be used to heat the root area. These are available at nursery supply houses.

When watering, tepid water should be used. Cultivators using systems that recirculate water can heat the water with a fish tank heater and thermostat. If the air is cool, 45-60 degrees, the water can be heated to 90 degrees. If the air is warm, over 60 degrees, a 70 degree water temperature is sufficient.

Gardens using artificial lighting can generate high air temperatures. Each 1000 watt metal halide and ballast emits just a little less energy than a 10 amp heater. Several lights can raise the temperature to an intolerable level. In this case, a heat exchanger is required. A venting fan can be used to lower temperatures.
Greenhouses can also get very hot during the summer. If the sun is producing too much heat, opaquing paint may lower the amount of light and heat entering the greenhouse. Fans and cooling mats also help. Cooling mats are fibrous plastic mats which hold moisture and which can be purchased through nursery supply houses. Fans blow air through the mats, lowering the greenhouse temperature. They are most effective in hot, dry areas.


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#2 anigav



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Posted 22 July 2009 - 12:06 PM

Ideally the temp should be from 65 - 75 because this will give you the most chemical activity in the root zone and aid in proper nutrient uptake. This doesn't mean they cant survive at other temps but this is ideal. If your feeder roots get destroyed from heat, they can take one to two weeks to grow back. We all know cuttings will root better at slightly higher temps 80 - 85. One thing some people don't always factor in is the temp of the water used for watering the plants. Soil usually buffers temps better so warm water can have a positive or neg effect depending on your starting soil temp. Larger reservoirs will have similar effects. Generally, falling outside the ideal temp won't have a large effect unless it is extreme, prolonged or dry. Too hot can aid in fungal growth, pest reproduction and additional humidity from water evaporation. Many of us have probably had a slimy root problem because of an overheated res at some point. If its too cold growth begins to slow and even colder/freezing will almost stop nutrient uptake. Some strains can cope with certain extremes better than others.

Now look at it from a human perspective. Humans have adapted to all sorts of climates. Most of us are accustomed to a specific range of temperature. This is why most office buildings are between 70 - 75 degrees. This doesn't mean we couldn't work at 85-100 degrees but temps like that would get people stressed and some would simply quit working.

All in all, I think that everyone should have a temp gauge for their soil or res and figure out what works best with your strain to keep a healthy root system. If you disagree, I don't need all the ,"My plants grow fine at 100 crap." If a temp works for you go for it. But if your unsure, stick to a root temp of 65 - 75 for a start.

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#3 blueridge_bandit


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Posted 22 July 2009 - 05:49 PM

i'm somehow reminded of american pie. weird. sorry for the offtopic.

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i am not a mod btw.
it just had to be colored blue because of my name that has blue in it.

#4 Rebel Dawg

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Posted 22 July 2009 - 07:26 PM

buddha and anigav, you two did a great job of covering all bases. Great tem work.

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#5 Buddha



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Posted 23 July 2009 - 09:35 AM

I was in the grow shop and was talking to some people about this subject.

It was discussed, that plants in a hot enviroment, will take in much more water, using Transpiration to cool it's self. If there is the regular amount of salts(Nutes) in the water, the plant will take them in as well, resulting over fertilization.

This could be and is a very important thing to know.

Your PPM is well into the safe zone that you have always used, but your plants are frying..."WHY????...What's going on????"

Check the room temperatures, if the plants are hot and trying to cool themselves, this could be your problem.

Along with the water the plants are taking in, the plants are taking in salts. We agreed in our conversation, that when temperatures are higher then normal, the salts should be dropped low, to 300 PPM. This way the plant could cool it's self with all the water it needs and get the nutes it needs also, without frying it's self.

This should not be used as a way to cool your plants. This can be used as a way to possibly save plants for a short period of time in an emergency, or a way to diagnose a problem. Also...I have never used this method, it would be totally up to the grower wheather this would apply to there situation and a good idea to try.



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#6 anigav



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Posted 23 July 2009 - 11:39 AM

I have had heat issues many times and reducing nutes has always saved me.

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