1. Combine first 5 ingredients in a 6-quart electric slow cooker. Cover and cook on LOW for 8 hours.
2. Mash the fruit to a chunky puree with a potato masher. Increase heat to HIGH; cook, uncovered, 4 hours. Turn off heat, and nestle rosemary sprig into fruit mixture; let stand 1 hour. Remove and discard rosemary sprig and any loose needles. Place jam in a bowl; cover and chill 8 hours. Store, refrigerated, for up to 3 weeks.
* A number of manufacturers make pectin for low-sugar recipes; depending on the brand, you may need to use more or less than we call for. Read the instructions on the package, and use the recommended amount for the quantity of fruit being used.