As a gardener, you know that the correct temperature is crucial for the growth and development of your plants. But what is the ideal water temperature for growing cannabis?
Cannabis thrives in temperatures between 70 and 85º F. However, the specific water temperature best for your plants will depend on your growing environment.
In this segment of Ask the Garden Sage, professional grower David Robinson explains what happens to the cannabis plant when exposed to different water temperatures.
Why Oxygen Matters
Oxygen is an essential element for all living things, and plants are no exception. When watering plants, it is vital to ensure that the water is oxygenated, as this will help the plants absorb the water and nutrients more effectively.
Plants watered with oxygen-deprived water may struggle to absorb the necessary nutrients, leading to stunted growth and potential health issues.
The amount of oxygen in water depends on many factors, including atmospheric pressure, water temperature, and water salinity.
You can use an aeration stone to oxygenate the water for your hydroponic garden. This will allow the water to become saturated with oxygen, which will benefit your plants’ health and growth.
Warm Water, Low Oxygen
“If the water is too warm, being over 70-72º F, the oxygen content of that water will be quite low. Low oxygen can eventually lead to an anaerobic environment in the root zone, opening the door to disease, specifically Pythium root disease,” warned the Garden Sage.
Some signs that your plant may suffer from Pythium root rot include yellowing or wilting leaves, reduced growth and vigor, and a foul smell emanating from the roots. The roots may also appear dark and mushy, and the plant may be more susceptible to other diseases and pests.
Cool Water, High Oxygen
“Colder water that is higher in oxygen will be more beneficial to our plants. Most of the time, 65º-67º F are considered ideal numbers,” suggested the Garden Sage.
However, maintaining this optimal temperature range in water can be challenging since grow room temperatures are between 72º-77º F for vegetative plants and 75º F for flowering plants or between 82º-84º F if using supplemental carbon dioxide during the vegetative stage.
Keep your water temperature in the ideal range by adding hot or cold water as needed, using cooling devices or bottles filled with ice, or keeping water in a cool area.
Recirculating Water Gardens
“There are some circumstances like recirculating water gardens where we are especially vulnerable to root disease where we can lower the water temperature even more, potentially down into the 60º F range,” suggested the Garden Sage.
Cold Water, Plant Shock
It is important to note that cannabis plants are sensitive to temperature changes. If the water temperature fluctuates too much, it can stress the plants and lead to poor growth. It is best to keep the water temperature consistent to ensure optimal growth.
The Garden Sage explains: “If we go too low, below 55º F, these lower numbers will cause slow growth and shock the plants. If every time they get water, they’re shocked, it’s going to reduce their metabolic capacity and overall growth and production, so it’s important that we have our water at that Goldilocks zone temperature of 65-67º F.”
Some signs that your plants may be experiencing cold shock include wilting or drooping leaves, discoloration of the leaves, and slowed or stunted growth.
How to Check Water Temperature
To check the temperature of the water you are using to water your cannabis plants, you will need a thermometer. Digital thermometers are generally more accurate and easier to read than analog thermometers, but either type will work.
To use the thermometer, simply fill a container with the water you will be using to water your plants and insert the thermometer into the water and wait a few seconds to get an accurate reading.
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