The common red radish is ready to harvest between 3/4 inch and 1 1/2 inches in diameter. Some radish varieties can get much bigger. Check your variety for the correct harvesting size. You may need to loosen the soil underneath with a garden fork before puling up the radishes.
Rinse thoroughly in cold water two or three times. If they have dirt stuck to them they may need to be soaked in cold water before rinsing. Radish bunches can be kept at room temperature in a bowl of water for 2 or 3 days. They’ll last a week or more in the refrigerator either in a bowl of water or in a plastic bag with a moist paper towel.
Links to More Information
How to Harvest Radishes https://www.wikihow.com/Harvest-Radishes
47 Radish Recipes that put the Rad back in Radish https://www.bonappetit.com/recipes/slideshow/radish-recipes