What Pot to use?
Venus Flytraps don’t have a typical root system that you see with many other plants. They only have a few very fine roots hanging from the bottom of the rhizome (base of the plant). The roots though can grow down to sizes of 6 inches or more so the size of your pot needs to accommodate this because you don’t want to have the roots of your flytrap sitting in the base of your pot and sitting in water all the time as it will develop root rot due to excessive damp conditions.
I have found that a pot that is around 4-5 inches seems to be ideal for my flytraps. They seem to thrive. Some of my larger flytraps I have put in much larger pots so that the roots aren’t always sitting in water.
What Soil do I use?
Venus Flytraps grow in very nutrient poor soil. This is what caused them to adapt to the environment and create the trap in the first place.
The easiest soil medium to use to pot up your flytrap is to use pure peat moss (make sure this has no added nutrients), when I started out I purchased a small 5 litre bag of peat moss from Bunnings for around $6 (the brand name was Brunnings).
Another soil medium you can use and also to make the small bag of peat moss go further is to get some washed sand from your local garden supplies (I have found that the sand needs washing with the garden hose to clean it up further) and mix this sand with your peat moss. Half peat moss and half sand. It will help aerate the soil so your flytrap won’t become waterlogged.
If you can’t bebothered with washing sand you could just grab a 5L bag of Perlite from Bunnings (around $9) and mix both it and your bag of peat moss together and use this as your potting medium. This is what a number of people use for flytraps and a range of different carnivorous plants. You may notice that if you have bought a standard flytrap from a nursery that it is potted up in this mix of peat and perlite. I don’t personally like the perlite mainly because it is light and seems to float in the pot and just gets everywhere.
You can also just experiment with a combination of peat moss, perlite, and washed sand. I have heard of people using mixes of peat:sand:perlite 50:25:25. Try it out for yourself though as everyone has a personal preference for what they like to use as a soil medium.
The last method I have seen and tried a little is to use pure long fibre sphagnum moss as your potting medium. It is trickier to deal with as it isn’t a uniform soil and it creates difficulty when putting your flytrap in it and putting it into a pot but I have noticed that the flytraps seem to thrive in it.