August is the peak season for yellow cherry plums, and in the Danish countryside, where my parents live, you’ll find them everywhere. They are growing at the field boundaries and along the roads, and maybe because there are so many of them, they are just left hanging on the trees (or is it bushes) since nobody cares to pick them. Some of the yellow cherry plums can be a bit mealy to the taste, while others are juicy and nice, and it turns out they all make a really nice jam.
In Denmark most people call the yellow cherry plums mirabelles, but we also call real mirabelle plums from France, which are different from cherry plums, mirabelles. I found out this is also the case in Germany and the UK, so I was not sure whether to call the plums mirabelles or cherry plums in this recipe, but I decided to stick with what is apparently the correct name for those little yellow plums (or are they berries?).
After pitting, the weight of the cherry plums will be approximately half of the initial weight. The recipe below is for 36 oz pitted yellow cherry plums, but you can use any quantity of yellow cherry plums. The added sugar should be 3/4 the weight of the pitted yellow cherry plums.
I used gelling sugar to make the jam in the photos of this recipe. Gelling sugar is granulated sugar with added pectin. Pectin is a naturally found in all fruits and berries, and when heated, this is what gives the jam its jelly-like texture. The pectin concentration varies within species with lemons and apples among the most pectin-rich fruits, and within the ripening cycle. Ripe fruit has less pectin and is thus more difficult to jam. Cherry plums should contain enough pectin to make the jam go thick, so you can do with regular sugar if you want. For the jam in the video below, I am using regular, granulated, sugar, and it took a bit longer (about 35 minutes) until the jam had the texture I wanted.
You can check the viscosity of the jam along the way by scooping up a bit of the jam on a spoon and put it in the fridge for a few seconds, or you can use a candy thermometer and wait for the temperature of the jam to reach 220°F (105°C) which is the gel point, i.e. the temperature point, when the jam starts thickening. Depending on how you choose to sterilize the jars, the jam can last up to 1 year.