Wash 4 cups of fresh mulberries and remove stems. In a pot, combine mulberries, 1/4 cup lemon juice, and grated zest. Crush 1/3 of the mulberries to release juices.

Sprinkle 1 cup of granulated cane sugar, a pinch of salt, and 2 tablespoons of low-methoxyl pectin into the pot. Stir and let rest for a few minutes.

Set the pot over medium-high heat, stirring constantly until the mixture bubbles. Bring to a rolling boil and stir for about 2 minutes.

Maintain a hard rolling boil for 5-7 minutes, stirring occasionally. The mixture will thicken.

Use a candy or digital thermometer to check that the mixture reaches 220°F (104°C). Alternatively, perform the plate test.

Remove from heat after achieving desired consistency. Let sit for 2 minutes, then transfer to clean canning jars.

Wipe the rims of the jars, seal properly, and refrigerate for up to 3 weeks or process for longer storage.