The leeks will throw up a round stem in the middle of the leaves, this will
grow to around 3 ft tall and will have flowers in the summer followed by
black seed, it also may have small pips or bulbuls. which can be planted.
The seed will be sown spring on 2005 to give you leeks 2005/6.
Unless they are special then I wouldn't bother, you are having your ground
taken up for a long time to save getting a packet of seed. They don't like
being transplanted once they are coming into flower so have to be left in
situe.
Try reading this.... http://www.llanor.fsnet.co.uk/Articles/971119.htm

As for Celeriac http://greennature.com/article2060.html

Both these were found doing a quick google search.........

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David Hill
Abacus nurseries
www.abacus-nurseries.co.uk