We have a number of varieties of plums growing in our yard. We have the purple Italian or prune plums that I make into prunes later in the fall. We also have three earlier varieties that I decided to mix and make into a Three Plum Jam.
The three plums I used are a round red variety similar to Santa Rosa plums, a round yellow plum that is very juicy and has a very short season and larger oval plum that turns a dark purple over time. We don't know the names of the fruit we have here, we just guess at them.
I didn't use a recipe as such, I just checked out a number of recipes on the internet and found the proportions for ingredients were similar in most.
12 c plums total (I used 4 cups of each kind)
½ c lemon juice
6 c sugar
2 c homemade pectin
Wash and sort plums of your choice.
Pit plums and cut into pieces if plums are firm. For the larger purplish red plums, I cut them into eighths.
As mentioned before, the yellow plums are very juicy. You more or less try to remove the pit and cut the skin into pieces without making a big mess. I often poke a hole with the knife and squeeze out the pits catching the juice and pulp in a bowl and then cut/rip the skin into pieces. If you eat one of these plums, you almost need to put the whole plum into your mouth before you bite it or else you will be covered in juice from your chin to your waist. They are not a plum to eat in public - you either look like a messy slob with juice dripping off your chin or a pig with a whole plum stuffed into your mouth.
The red plums were juicy as well so they were pitted and their skins chopped into smaller pieces just like the yellow ones.
Mix all ingredients in a large heavy pot and bring to a boil. Stir frequently for about 30 minutes or so. I actually had to cook them for almost an hour. The length of cooking time depends on how juicy your plums are. If I had used only the larger purplish/red plums, my cook time would have been shorter.
Skim off the foam and cook until it passed the jam test. (the saucer in the freezer mentioned in previous posts).
Pour into sterilized jars and process for 10 minutes in a hot water bath.
The recipe made 9 pints of lovely red jam. Isn't it a pretty colour! ;)