Spearmint is similar to peppermint grows like a weed but has different chemical makeup and scent.  Mainly used for digestive issues and calming the stomach.  Also known as a local anaesthetic, anti-spasmodic for digestive, helps heal sore gums. Uplifting, reduces stress and depression, good as decogestant for sinus issues. 
Beneficial as an insecticide, stimulant and anti-microbial.  With only a small amount of Menthol its excellent for children and all the digestive issues including hiccups with no skin irritation when applied topically however still dilute with a liquid carrier like coconut or almond oil.