How to Make It
Fill a large pot with water, cover and bring to a boil. Add the canning jars, lids and rings along with a set of tongs and a ladle and simmer over low heat for about 10 minutes to sterilize. Cover the pot and turn off the heat.
Set a metal rack in another large pot. Fill the pot with water and bring to a boil. Add the nectarines and boil until the skins loosen, about 30 seconds; using a slotted spoon, transfer them to a rimmed baking sheet and let cool. Peel, halve and pit the nectarines and cut them into 1/2-inch dice.
In a large, wide saucepan, combine the nectarines with the sugar, lemon juice and the candied, fresh and ground gingers. Bring to a boil over moderately high heat, stirring to dissolve the sugar and skimming the surface as necessary. Reduce the heat to moderate and simmer the jam, stirring once or twice, until it reaches 220° on a candy thermometer, about 40 minutes longer.
Using the sterilized tongs, remove the jars from the hot water and transfer to a large rimmed baking sheet. Ladle the jam into jars, leaving 1/2 inch at the top. Using the tongs, place the lids on the jars followed by the rings. Screw on the lids securely but not too tightly.
Using canning tongs, lower the jars into the boiling water of the pot with the rack at the bottom, making sure they are covered by at least 1 inch of water. Boil over high heat for 10 minutes. Using the canning tongs, transfer the jars to a rack to cool until the lids seal (they will look concave); refrigerate any jars that do not seal. Store the sealed jars in a cool, dark place for up to 6 months.