Fresh radishes straight from the garden are delicious. Radish ' Riesenbutter' (Raphanus sativus) is a radish with tender flesh that does not tend to go soft. ' Riesenbutter' grows rapidly & is a guaranteed success for any gardener. After four to six weeks the delicious & healthy radishes can be harvested. Radishes are vegetables that thrive almost anywhere. Riesenbutter is a very popular variety with large, crimson roots.