The bottom of your garter or ribbon snake’s terrarium should be covered with a substrate (bedding). Paper towels (unbleached), pine shavings, bark mulch, wood chips, shredded coconut husks, or recycled newspaper are good options. Cedar shavings should not be used, as they can affect the lungs and cause skin blisters. Anything used as a substrate must be absorbent to keep odors to a minimum. It also must be large enough to not stick to food items and be accidentally ingested.
Garter and ribbon snakes are often referred to as “snakes of the bushes,” which should give you an idea of the kind of foliage needs they have. Most hobbyists use artificial plants to avoid the potential disease-carrying problems associated with live plants. Also, artificial plants never need to be watered or cared for in any way. Spread some plants throughout the terrarium, covering areas of the bottom, sides, and higher portions.
These snakes, as most other snakes, will spend a good amount of time hiding. This is their natural way of avoiding stress, which can make them very sick. Providing some dense foliage is a good start, but they will also need at least one hide box. You can use a clay pot, a hollow piece of log, or choose from a variety of commercially-sold boxes. Keep in mind that snakes only get a feeling of security from a hide box when the box is an appropriate size, which means their body should be able to touch the box on all sides.
Garter and ribbons snakes are very adaptable creatures, including their high cold tolerance. However, they still require heat in their terrarium home. First, you must create a basking spot, a place where the snake can go whenever he needs to warm himself. To do this, your first option is placing an incandescent fixture, with a 60 to 75 watt bulb, on top of the terrarium. A second option is to place an undertank heating pad on the bottom outside of the terrarium. Either way, make sure your heating source is located at only one end of the space so that your snake can go somewhere else when he needs to cool down. The temperature throughout the tank should be 74° to 83°F, while the temperature in the basking spot should not exceed 88°F.
For more information, read Quick & Easy Garter & Ribbon Snake Care (T.F.H. Publications, Inc.).