I made this recipe up, and I am so pleased with the way it turned out!! The nectarines add just a little extra something to the plums, and the vanilla bean just highlights the flavors. Best of all, it comes out the most beautiful color...
3-4 quarts of small wild plums, pitted
2 large nectarines, pitted and coarsely chopped
Juice of one large lemon
1 vanilla bean, sliced in half length-wise
Lots of sugar, to taste
12 half-pint jelly jars
Combine all the ingredients in a big pot and bring to a boil, while mashing the fruit with a potato masher. As the mixture boils, a foam should form on the top of the pot. Skim this off, being careful not to mix it into the fruit. After you've removed the foam, continue to boil for about an hour, stirring occasionally. To see if it's done, dip a spoon in the jam and place it on a plate in the freezer for a few minutes. When you take the spoon out of the freezer, run a fingertip down the back of the spoon. If it leaves a trail, the jam is firm enough. When in doubt, let it boil a little longer. Remove the vanilla bean and pour into jars.
Now for canning: I have a great steam canning pot that my father gave me, and it makes my job MUCH easier. These are pretty easy to find, and I think they're a worthwhile investment if you are planning to can a lot (and once you see how easy it is, you probably will!). However, it is also pretty easy to just use a big stock pot and boil the jars.
The most important things to remember are to make sure you wipe the rims of the jars after you fill them, and to not tighten the lids too much. Once you have the jam in the jars and the lids on, place them in your canning pot, or in a large stock pot with a wire rack in the bottom and cover with water. Make sure the jars are spaced at least an inch apart. Bring the water to a boil. If using a steam canner, wait until the steam comes out in long columns. Boil/ steam for about 10-15 minutes. Remove the jars from the pot with canning tongs (SO useful if you don't want to burn your arms), and place on a towel to cool.