Examine the exterior of the jicama. Select those with an approximate 6-inch diameter and a smooth, cream or light brown exterior. Avoid wrinkled jicama roots as these are overly-mature.
Check all sides of the jicama for cracks. Avoid those with cracks or visible bruises.
Cut into the jicama. Under-ripe jicamas are hard and difficult to cut while a knife easily slices through a ripe jicama.
Harvest garden-grown jicama after the foliage begins to die back but before the first fall frost. Dying foliage indicates root maturity.