Peach and Rhubarb Jam
5 C. peeled, pitted, and chopped peaches (about 8 medium peaches)
4 C. trimmed and diced rhubarb, in 1/3-inch (9 mm) dice
5 C. granulated sugar, or a little less to taste
24 lemon seeds, tied in cheesecloth or placed in a tea strainer (from 3 lemons)
In a large bowl, combine the peaches, rhubarb, and sugar and stir well. Cover and let stand at room temperature for 12 hours, stirring occasionally, to draw out the peach juice and dissolve the sugar. Transfer the mixture to a heavy 8-quart (8-l) pot over medium heat. Add the lemon seeds and bring to a boil, stirring often and skimming any surface foam. Adjust the heat to maintain a steady but gentle boil and cook, stirring occasionally to prevent the fruit from sticking to the bottom of the pot, until the mixture thickens to a jam consistency and registers 220Â°F (105Â°C) on an instant-read thermometer, 45 to 60 minutes. While the jam is cooking, fill a large pot or canner, fitted with a rack, with enough water to cover the jars. Over high heat, bring the water to a boil. Reduce heat to maintain a simmer and place the clean, empty canning jars in the water for 10 minutes to sterilize them. When the jam is ready, use canning tongs to carefully remove the jars and drain any water inside. Alternatively, you can heat your jars in the dishwasher, however, you will still need the hot water bath ready for canning the jam. Remove the cheesecloth or tea strainer with the lemon seeds from the jam. Spoon the hot jam into the jars, filling to within 1/2 inch (12 mm) of the top. Wipe the rim clean with a towel dipped in hot water. Top the jars with the lids and twist on the screw bands. Set the jars, not touching one another, in the boiling water on the rack in the pot or canner. Make sure the water covers the jars by at least 1 inch (25 mm). Boil for 20 minutes, then turn off the heat and use tongs to transfer the jars to a rack to cool completely. When the jars are completely cool, press on the center of each lid. If the lid remains concave, the seal is good. Store the jars in a cool pantry for up to 1 year. If a lid failed the seal test, that simply means you get immediate gratification and should store the jar in the refrigerator and consume the jam within 3 weeks.