Short answers, pulled from the story.
A radish is a flowering plant in the mustard family, Brassicaceae, known scientifically as Raphanus sativus. Its large taproot is commonly used as a root vegetable, though the entire plant is edible and its leaves can be used as a leaf vegetable.
Scientists have tentatively located the origin of Raphanus sativus in Southeast Asia, the only region where truly wild forms have been discovered. India, central China, and Central Asia appear to have been secondary centers where different forms developed, and radishes enter the historical record in the third century BC.
Radishes owe their sharp, peppery flavor to chemical compounds including glucosinolate, myrosinase, and isothiocyanate. When the raw flesh is chewed, glucosinolates and the enzyme myrosinase combine to form allyl isothiocyanates, the same compounds found in mustard, horseradish, and wasabi.
Radish seed germinates in three to four days in moist soil with temperatures between 65 and 85 degrees Fahrenheit. Under average conditions the crop matures in three to four weeks, though colder weather may require six to seven weeks.
Radishes include spring or summer types such as 'Cherry Belle', 'White Icicle', and 'French Breakfast', and winter varieties such as 'Black Spanish' and daikon. The Sakurajima radish is a giant form typically grown to around 10 kilograms that can reach 30 kilograms if left in the ground.
The Night of the Radishes, or Noche de los rabanos, is celebrated by citizens of Oaxaca, Mexico, on December 23 as part of Christmas celebrations. In this folk art competition, large radishes up to 50 centimeters long and weighing up to 3 kilograms are carved into religious and popular figures and displayed in the town square.