General Gardening [WiP] Tips & Tricks guide to container gardening

One thing people don't always think of is soil temperatures and how it can affect your plants.

The temperature of your potting mix can be much higher than the ambient temperature. It can easily be 10 or more degrees higher. High soil temperatures (even in the mid-30's) for a prolonged time can be damaging, hence why we should take care in keeping our soil cool.
The opposite can also be true; if you live in a cold climate, the ground may take a much longer time to warm up than the ambient air.

How to control potted soil temperatures​

Keeping your soil in the right temperatures can be done in many ways, and your preference can differ per situation. Also note that each plant may have different heat ranges, so not all plants necessarily need to be protected in the same way.

Shade​

Shading your pots can help keep the soil temperatures down. In some situations you can simply move the pots in a low location where it's shaded. Do bear in mind that your plant might need a certain amount of sunlight. In some cases you only need to avoid the hottest parts of the day (usually around midday).
Shadecloth is a versatile item, which can help in both protecting your plant and soil from the harshness and heat from the sun. This is a great option for raised garden beds or to expand area of shade so you have more areas to work with. Shadecloth can also be adjusted easily with the seasons, and removed once it's not needed anymore. You can also locate the cloth in the right position, where it cuts out the sun during noon, but allows for morning and evening sun.

Mulch​

Mulch can help in many ways. It can help retain soil moisture, minimize weeds, but also helps insulate your pots. The insulative layer means that the soil heats up slower and in cold climates is can also mean it helps retain some warmth.
There are many types of mulch, each with their own properties. Straw and cane mulch are great insulating mulches that can assist in overwintering plants, and also keep the soil cool in summer. Grass clippings can help in warming soil up as they break down quickly, raising temperature as they decompose. Leaves can also be used as a layer on top of the soil, helping to insulate and retain soil temperature. Black mulch attracts sunlight and thusly heat up the soil faster.
I mostly recommend using what is available to you in your area. Whereas we have cane mulch readily available, you might not and will have to look for options you have. Each mulch has their own benefits, so look for what helps your situation.

Containers​

Plastic containers, in particular black plastic pots, tend to heat up much quicker than pots made of materials such as terracotta, concrete or stone. A thicker pot can also help insulate for longer than a thin-walled pot.
Black plastic pots are the most common around, and are often seen used in nurseries. They are more prone to overheating. It's recommended to repot plants you have bought, but if you can't a way to help insulate is by using a larger (often a decorative and/or ceramic) pot. You place your plant, plastic pot and all inside, using the cover pot to create an airspace that helps insulate your soil. The outer pot can help insulate against both winter and summer temperatures.
[@Grandmother Goose added:] When a dry heatwave (or just summer in some places) is causing pot plants to dry out much too fast, instead of watering them 4 times a day which can be too much to keep up with for most people, they can be cooled down and kept moist by putting the pot into a much larger pot with regular dirt, sand, or straw packed between the two pots, then add extra mulch on top of both. The second larger pot will not only insulate and keep the inner pot cooler, it'll also absorb some excess water which can then wick back to the inner pot without being so wet as to cause the plant's roots to rot. The same trick can also be used in winter in cooler climates to help keep things like bananas and galangal alive by insulating their pot and thus their roots from the cold, but in that case straw is king because it'll create it's own warmth as it decomposes.

Watering​

Watering your plants can also help bring the temperature down. When the water evaporates, it often helps to bring down the soil temperature. This is often best done in combination with mulch and/or shade.
Do keep in mind that if your plant's roots have already been damaged, it might not be able to absorb enough water so survive.


Do you have more knowledge on this? Kindly send your information to @Mandy Onderwater . Corrections, additions and questions are always welcome!