Cut your nectarine halves into 4 pieces

Combine with sugar and lemon juice and let macerate for 1-2 days in the refrigerator, stirring from time to time.

Prepare your canning supplies by making sure your jars, lids and all canning equipment are clean. I always run mine through the dishwasher the day I'm canning even though they are already clean, just to be sure. Once out of the dishwasher, I put my canning stuff on a rimmed cookie sheet, cover it with a towel and place it in the oven just to keep in clean and out of the way.

When you are done macerating your nectarines, stir the contents well to make sure all the sugar that may have settled at the bottom of the bowl is incorporated.

Transfer the nectarines and all the liquid to a large preserving pan and bring to a boil for 5 minutes over high heat, stirring frequently.

Place a sauce with a couple metal spoons in the freezer to use to test the jam later.

Lower heat and remove the foam that accumulates on the top of your jam with a slotted spoon.

Mash nectarines with potato masher and return to boiling .

Cook for 25-45 minutes until jam is thick, stirring frequently.

Reduce the heat if your jam starts to stick to the bottom of your pan

Test your jam with a spoon in your freezer to see if it is done, by scooping a small amount jam on a frozen spoon and then returning spoon to freezer for a few minutes. If the jam is thick and wrinkles a wee bit or moves when you push it with your finger, it is done. If it is still thin and you can't push it, return it to the heat for a couple more minutes, using the spoon test to check again.

When jam is set, stir in elderflower syrup and stir to combine.

Pour your jam into your sterilized jars, leaving 1/4" headspace.

Process in boiling water bath canner for 10 minutes.

At the end of 10 minutes, turn off the heat and let sit for 5 minutes with the lid of the pot removed

After 5 minutes, remove the jars and let sit undisturbed for 24 hours.

After 1 hour, check to see that all your lids have sealed. If any have not, refrigerate those.

This recipe assumes a basic knowledge of water bath canning. If you are a new canner, please research the process at the UGA website referenced above or in the Ball book referenced above.