Centimetres.

Their 13 cm high plant specimen had a 456 cm deep root.

So like 15 feet

Or 4 Emperor penguins

That's about four and a half AR-15 assault rilfes

Depends if they're imperial Emperor penguins

US customary

It says cm, so centimeters (1/100 meter) - slightly less than 0.4 inches

decimal place issues... I hope.

there are ten mm in a cm

456cm == 4560mm

there are 24.5 mm per inch (it is the law).

4550mm / 25.4 = 179.527 inches

or about 14.9 feet

which is about 5 yards

which is 20% of a 'murican football field if that helps

The above comment was pointing out that each 1 centimeter is slightly less than 0.4 inches. If you want to be more precise, each centimeter is about 0.3937 inches.

Your correction to my perception of what you intended 0.4 inches to represent is accepted.