Spinach

Spinach originated in ancient Persia -- roughly modern-day Iran -- an estimated 2,000 years ago, likely cultivated from a wild edible relative. From there it traveled east first: the king of Nepal reportedly sent spinach to China as a diplomatic gift in the 7th century.

Its path west was slower. Moors introduced spinach to Spain around the 11th century, and it didn't reach England and France until the 14th century, prized for appearing in early spring when little other fresh produce was available. Spinach's popularity in Europe surged in the 16th century in part due to Catherine de Medici, who is said to have insisted on it being served at every meal.

Spinach is unusual among leafy greens in tolerating real cold -- it germinates in soil as cool as 35 degrees F, far colder than lettuce needs, making it one of the earliest crops gardeners can direct-sow in spring or even overwinter in mild climates.

That cold tolerance comes with a matching heat sensitivity. Rising temperatures and lengthening daylight push spinach into dormancy and then bolting, typically once soil temperatures climb above roughly 80 degrees F, which is why spinach is treated as a cool-season crop grown in spring and fall rather than through summer.