Red Marble Onion 200 Seeds #0614 Item Upc#650348692018 75 days. Small, flat, red cipollini with a thin neck. 200 Seeds. Red Marble's dark red color goes deep into the rings. Avg. 1 1/2-1 3/4" diameter by 3/4-1" depth. Hard, good storage variety. In April or early May, or as soon as the soil can be prepared in early spring, sow in a 2" wide band, about 2 seeds/in., 1/4- 1/2" deep, rows 12-18" apart. Thin to 1 1/2-2" apart for highest yields in fertile soil. Thin to 3-4" apart for larger onions and 4" apart for the "sweet mild" type.