Prepare a boiling water bath canner and enough jars to hold 5 pints of jam.
Place chopped nectarines into a large, non-reactive pot that can hold at least 6 quarts.
Measure out sugar and whisk in the pectin, cinnamon, nutmeg, and cloves. Add the spiked sugar to the fruit and stir to combine. Let the fruit sit for a few minutes, until sugar starts to dissolve and begins to look syrupy.
Place pan of fruit on the stove over high heat and bring to a boil, stirring regularly. Cook at a rapid boil for 15 to 20 minutes, until the fruit softens.
Once the fruit is quite soft, use a potato masher to break the fruit down into smaller pieces. Stir in the lemon zest and juice. Continue to cook until the jam has thickened and passes set tests.
Remove jam from heat and funnel into prepared jars. Wipe rims, apply lids and rings, and process in a boiling water bath canner for ten minutes.
When time is up, remove jars from canner and place on a folded kitchen towel to cool. When the jars are cooled, check the seal by pressing on the top of the jar. If there’s no movement, the jar has sealed. Store up to one year in a cool, dark place.