Most all citrus trees sold by nurseries are grafted trees, where a desirable variety is grafted or budded onto a usually undesirable (as far as being eatable) rootstock. Unless you know for sure that your tree's were seedlings, they are very probably grafted, and will re-grow only as the undesirable root stock. However, you can graft any variety of citrus onto the surviving rootstock and again have some wonderful trees. - Millet