30 days — The plants have tall
tops with roots that are crimson to scarlet skinned, globe to top-shaped, with tender, crisp, white, mild flesh. We prefer harvesting them young when they are about one and a half to two inches in diameter. But given ample room, they can grow to be about the size of a baseball and remain of good, solid, usable quality.
H. A. Dreer, in a 1910 booklet that they published, had this to say about 'Crimson Giant' radishes, "This variety is suitable both for forcing or early planting out of doors. A remarkable feature of this Radish is that it will grow double the size of other round red forcing Radishes and still remain solid. The ordinary forcing Radish, after growing to the size of two or three inches in circumference, becomes pithy, while the Crimson Giant will grow to six and seven inches in circumference and still remain solid and juicy, free from all signs of becoming soft.
I have not yet tried letting them get that big here on our farm so I cannot confirm Henry Dreer's claim. Perhaps this next summer I will let them grow for a few months. Each packet contains two grams, which is approximately 200 seeds.