Environmental issues pertain to both problems with the environment above and below your plant.
Over- and Under-Watering
While under-watering is easy to solve, over-watering is much harder to deal with; however, diagnosing over- and under-watering is harder than it sounds because the problem is that both share the same characteristics of droopy leaves. The big difference, though, is that the stems of under-watered plants will droop as well, while the stems of an over-watered plant will stay upright, with only the leaves drooping. Another easy way to tell which one is affecting your plant is to check the soil one to two inches down when the leaves looks limp. If the soil in the middle of the pot is wet, then it is due to over-watering. If it is completely dry, then the plant is under-watered.
The fix for an under-watered plant is to just water it. However, the fix for an over-watered plant will depend on a number of factors.
If you are using a fabric pot, then you can most likely just wait it out until the excess water has evaporated through the pot before watering again. However, if you are using a solid pot you will need to make sure that the water isn’t clogged in the pot by first checking the drainage holes. If the water looks like it might take too long to dissipate, you can take a stick to poke some holes into the top of the soil to help with aeration; just be careful not to damage the roots. Also, if you are able to increase the temperature and lower the humidity to help the water evaporate quicker from the top of the soil, be sure to do so and then return it to normal once the soil is dry. Drying the soil fast when it has been waterlogged for a long period of time is important because not only are you trying to stop the plant from drowning, but waterlogged soil also creates the perfect environment for bugs to nest and root rot to appear.
When it comes to heat problems, there are actually 2 separate categories: overall heat issues and spot-heating issues caused by grow lights.
Overall heat issues typically start to appear If the temperature overall is over ninety degrees Fahrenheit, which will cause the entire plant to start to wilt with the leaves curling and shriveling to the heat. If this happens, the plants will need to cool down to recover, and this can be done in a variety of ways, from placing the plant under the shade, providing additional ventilation and airflow, or utilizing a cooling solution like an air conditioning unit.
If only the top leaves look like they are burning up, turning yellow, or completely burned, then that is a spot-heating issue caused by a grow light being too close to the plant. The simple fix it to move the lights farther from the plant.
When cannabis is too cold, the plant will decline significantly in growth because the plant's metabolism will slow down in colder weather, which also causes it to perspire less, leading to the plant taking in less water and nutrients. This in itself is not life-threatening to the plant; to boost the growth speed again, you will need to warm the grow space with a portable heater, greenhouse or any other form of insulation. If using fabric pots, repotting the plant in something with more insulation to the roots like a clay pot will help as well. For indoor plants, you can also use an HID grow light, which produces a good amount of heat when on.
Humidity is usually overlooked for a number of reasons: you cannot gauge humidity the same way you can easily gauge temperature just by feel unless the weather is already near an extreme, and since a plant generally can still grow in a wide range of humidity scenarios from 20−80%, you will almost never be in an environment that a plant shows any symptoms due to humidity extremes without an accompanied temperature extreme that affects the plant first.
A high humidity will cause a plant to perspire less, which leads to less water and nutrient uptake, slowing the overall plant growth. A low humidity will surprisingly do the same, as the pores in the leaves will close up, leading to no perspiration in the plant, which will also slow overall plant growth. So, if the humidity issue is only temporary due to weather fluctuations, a short-term fix is to increase the airflow to the plants to combat high humidity, and misting your plants with water to combat low humidity. For a long-term solution, a humidifier or a dehumidifier are the best options.
A strong wind will prevent a number of bugs, mold, and mildew from being able to have the time on a plant to settle down; however, there is such a thing as too much wind. If your leaves looked damaged, especially at the tips, looking similar to that of a watering issue but only affecting the leaves near a wind source, then your plants have wind damage from the airflow being too strong, and all you need to do if this happens is tone it back a little or move the fan further away.
Did this guide help? This article was taken directly from The Absolute Beginner's Guide to Growing Cannabis book, so if you like the advice above you'll love the rest of the book, which includes a lot of exclusive content not found anywhere else. You can find both the e-book and paperback copy on Amazon, and it's free with a Kindle Unlimited subscription!