Begin by washing your fresh rhubarb stalks thoroughly under cool water. Trim off the ends and any leaves, then cut the stalks into 1-inch pieces. If you're using ginger, peel and chop a small piece, then combine it with the rhubarb in a large bowl.

Sprinkle the sugar evenly over the rhubarb mixture. Stir gently but thoroughly to combine, ensuring the sugar interacts with the rhubarb. Cover the bowl with plastic wrap and refrigerate it overnight.

Preheat your oven to 120°C (250°F). Wash your canning jars and lids in hot, soapy water, then place them on a baking tray. Once the oven reaches the desired temperature, put the jars and lids in to sterilize for about 15 minutes.

In a large saucepan, pour the chilled rhubarb mixture and all its juices. Heat over medium until the sugar has completely dissolved, which should take about 5-10 minutes. Once dissolved, add the lemon juice and bring the mixture to a rolling boil. Cook for 20-25 minutes, stirring constantly, until the jam thickens.

After cooking, remove the saucepan from heat and let it cool for about 5 minutes. Carefully ladle the hot rhubarb jam into your sterilized jars, filling them while still warm.

Allow the jars of jam to cool at room temperature for several hours. Check the seals to ensure they are tight before storing. Place the sealed jars in your pantry for up to a year.