Celeriac Plants and Seeds are readily available for sale from online suppliers. Growing celariac from seed is fairly simple and Celariac makes a great winter vegetable. 'Giant Prague' is a popular variety and is often used to make a celariac mash or in soups. Celariac seedlings can be planted out in November in cooler areas and will take 2-3 months before thay are ready to harvest. In sub tropical areas a second planting in May will produce good results.