Prepare the thimbleberries by rinsing them gently under cool water and removing any stems or debris. Wipe the fruits well and cut any large berries in half.

In a large saucepan, gently toss the sugar on the thimbleberries.

Stir gently to coat the berries evenly with sugar. See the tip below for doing this process overnight.

Place the saucepan over medium heat until the sugar is dissolved.

Increase the heat from medium to high and bring the mixture to a rolling boil, stirring occasionally to prevent sticking.

Stir in the lemon juice once boiling to enhance the flavor and aid in the preservation process.

Boil for another 15 minutes or until the jam reaches 220F or 105C.

Stir often making sure the jam doesn’t burn and continue to boil for around 15 minutes or until the jam reaches 220F or 105C. At this point, you should see that the berries have softened and the mixture has thickened and bubbles completely cover the surface of the jam. See the tip below to understand when the jam is done.

Remove the saucepan from the heat.

Transfer the jam into sterilized jars, leaving a quarter-inch of headspace.

Seal the jars tightly.

Allow the jars to cool completely at room temperature before storing them in the refrigerator or a cool, dark pantry