Garter snakes are often described as “small pet snakes“, but how small is small?
Some garter snakes will only be about 2 feet (50 cm) long when they are fully grown. Others will grow as long as 5 feet (125 cm).
Setting up a vivarium for a garter snake you expect to be 2 feet long that keeps on until it is 5 feet long is traumatic for the snake and for the owner.
The best way to know how big your garter snake will get is to be very sure about its species—different species of garter snakes have very different growth potential.
Most garter snakes for sale in North America are wild-caught. They are supposed to be identified before they are ever shipped to the pet store, but often they are not.
Even when your pet store has the correct identification for the garter snakes it offers for sale, most buyers will quickly forget it.
So, in this article, we will tell you how to recognize what kind of garter snake you have and tell you how much to expect it to grow.
First, Make Sure You Really Have a Garter Snake
Garter snakes and water snakes look a lot alike, live in the same places, and are often caught together.
They require similar care, but won’t give you the same experience once they are grown.
The way to tell the difference between a garter snake and a water snake is to look at their rear ends.
The cloaca, or rear opening, of a garter snake, is covered by a single, solid scale. The cloaca of a water snake is split in two.
Once you are sure you have a garter snake, then you need to determine the species of garter snake to know how big you can expect it to grow.
How Big Do Garter Snakes Get (by Species)
Let’s look at how big usually different species of garter snake get.
If you want a quick run down, I have made this table for you (with more details about each species after the table).
| Garter Snake Species | Size |
|---|---|
| Aquatic Garter Snake | Up to 4 feet (122 cm) |
| Black-Necked Garter Snake | Up to 3 feet (91 cm) |
| Butler’s Garter Snake | 15 to 20 inches (38 to 51 cm) |
| Checkered Garter Snake | 24 to 30 inches (61 to 76 cm) |
| Common Garter Snake | 18 to 26 inches (46 to 66 cm) |
| Florida Garter Snake | 20 to 26 inches (51 to 71 cm) |
| Plains Garter Snake | 20 to 28 inches (51 to 71 cm) |
| San Francisco Garter Snake | 18 to 26 inches (46 to 66 cm) |
| Western Terrestrial Garter Snake | Up to 3 feet (90 cm) |
Aquatic Garter Snake
The aquatic garter snake (Thamnophis couchii) ranges from southwestern Oregon down to Baja California, and from coastal California inland to Nevada.
It’s tied with the giant garter snake as the largest of all garter snakes, frequently reaching 4 feet (122 cm) long.
However, there is considerable variation among the subspecies of aquatic garter snakes, one subspecies getting no longer than 18 inches (45 cm) and another reaching as long as 57 inches (145 cm).
The biggest aquatic garter snake can be recognized by its olive-brown skin and black spots in a checker pattern running down its back.
This extra-large garter snake is active during the day, when it is easier to watch, and rests at night.
It likes to dangle itself from a tree limb to catch the rays of the sun or its heat lamp.
Aquatic garter snakes aren’t particularly friendly.
In nature, they release musk and retreat into the water. In captivity, they will make your hand stinky with musk if they feel threatened.
Black-Necked Garter Snake
From southeastern Utah, southern Colorado, eastern Arizona, and all of New Mexico, south through Mexico to Belize and Honduras, the black-necked garter snake (Thamnophis cyrtopsis) is found near streams, rivers, and cattle watering tanks, taking a drink before resuming its crawl across the desert to look for food.
Another kind of garter snake that prefers to be active during the day rather than at night, the black-necked garter snake is found basking on rocks or hiding beneath water troughs.
The top of the head of this snake is dark blue to black.
It has two large black blotches just behind its head, separated by the orange stripe that runs down the middle of its back.
It has side stripes of gray or yellow, and sometimes has spots of black or blue. Black-necked garter snakes are mild-mannered and adapt well to being kept as pets.
The largest black-necked garter snakes are about 3 feet (91 cm) long when full-grown.
Butler’s Garter Snake
Butler’s garter snake (Thamnophis butler) is collected on the shores of lakes and marshes in eastern Michigan, southwestern Ontario, and northwestern Ohio.
It likes to spend most of its time under logs or in thick grass, but it will come up to warm itself on a sunny afternoon.
This garter snake has three stripes that run the length of its body.
The stripe down the middle of its back is a light yellow. The two stripes on either side of it are yellow or orange.
It may have black spots between the stripes, and usually has a belly of a mottled green.
Butler’s garter snake sometimes grows as long as 27 inches (68 cm), but most specimens are only 15 to 20 inches (38 to 51 cm) long fully grown.
It brumates for four or five months every winter. When a female gives birth, the hatchlings are so small that they have to be fed chopped earthworms by hand.
Checkered Garter Snake
The checkered garter snake (Thamnophis marcianus) is found near water in dry grasslands from central Texas west to California.
It is a very attractively colored species that has a dark checkerboard pattern on its back, over a yellow background.
It usually has a yellow stripe running down its back.
This species of a garter snake is a favorite of breeders who sell garter snakes to pet shops.
It is one of the heavier and longer garter snakes, usually growing 24 to 30 inches (61 to 76 cm) long.
However, some shorter specimens of this snake will be just 18 inches (45 cm) when fully grown, while others will be 42 inches (107 cm).
Common Garter Snake
The common garter snake (Thamnophis sirtalis) is found in wet locations across 48 continental states of the United States except Arizona.
Eastern subspecies of this garter snake have a yellow dorsal stripe on a background of olive, black, green, or brown.
Western subspecies of this snake produce the same colors but also an albino morph.
Most specimens of this snake grow to a length of just 18 to 26 inches (46 to 66 cm) at full maturity.
Occasionally, a common garter snake will grow up to 4 feet (122 cm) long.
Florida Garter Snake
The Florida garter snake is a common garter snake with bright blue stripes on its sides.
The stripe running down the middle of the snake’s back is dull tan to yellow.
The typical length is 20 to 26 inches (51 to 71 cm), maxing out at 39 inches (99 cm).
Plains Garter Snake
The plains garter snake ranges from south-central Canada south to Missouri, Kansas, and Colorado. It is another garter snake that prefers to be active during the day.
It is found near water in dry, grassy areas. The stripe on its back is usually bright yellow, but can be orange.
It has side stripes of green, blue, or gray.
Typical adult lengths of the plains garter snake are 20 to 28 inches (51 to 71 cm) long.
Occasionally, a plains garter snake will grow to be as much as 40 inches (102 cm) long.
San Francisco Garter Snake
This endangered common garter snake is considered one of the most beautiful snakes on the planet.
A wide greenish yellow back stripe that is edged with black is bordered by red stripes on either side and then a black stripe on either side of that.
The top of its head is red, while its underbelly is blue. The San Francisco garter snake is only found in the wild in part of San Mateo County in California.
The only place you are likely to see this garter snake is in a zoo. It grows from 18 to 26 inches (46 to 66 cm) long.
Western Terrestrial Garter Snake
The western terrestrial garter snake (Thamnophis elegans) is collected over a wide area from Baja California to Texas and north to Canada.
It is at home in the mountains at 9,000 feet (3,000 meters) and in lowland deserts. It can live in forests and grasslands.
It can survive in places where there are cold winters and in places where there are no winters at all.
This garter snake is most likely to be captured in the winter when it gathers in large numbers in caves and basements to escape the cold.
In the summer, it likes to bask on rocks, where it is caught in smaller numbers. Because this species of garter snake is found in so many places, it is not a picky eater.
You will have fewer problems getting western terrestrial garter snakes to eat than other species.
Its basic body color is brown with a single light yellow stripe down its back. The mountain terrestrial garter snake (Thamnophis elegans elegans) has two additional, colorful stripes on its sides.
Adults grow up to 3 feet (90 cm) long. If mated pairs of this species are given a five-month period for brumation, the female will usually give birth to 10 to 15 baby snakes every year.
You will need to remove the hatchlings as soon as they are born, however, or the mother snake will often eat them and the male snake with which she mated.
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