2 pounds rhubarb
3 cups granulated sugar
Juice of 1 lemon or of ½ orange and ½ lemon
Wash, trim and dice the rhubarb. You will have about 8 cups.
In a large pot combine the rhubarb, sugar, and citrus juice and toss to mix. Bring the rhubarb mixture to a boil over medium-high heat and cook for 2 minutes. Remove the pot from the heat and let sit for 1 to 2 hours.
Set a stockpot on the stove and fill with enough water to cover the jars by 1 to 2 inches. Bring the water to a boil over medium-high heat. Sterilize the jars in the water bath.
For a jam with some texture, set a colander over a bowl and, using a slotted spoon, transfer the rhubarb to the colander. Bring the juices to a boil over medium-high heat and cook until thickened. Add the rhubarb back to the pot, along with any juices that have collected in the bowl under the colander. Bring to a boil over medium-high heat, stirring frequently, and cook about 5 minutes longer.
For the smoother jam, cook the fruit with the juices over medium-high heat for 15 to 20 minutes. Remove the pot from the heat.
Bring the water bath back to a boil. Simmer the lids in a saucepan of hot water. Ladle the jam into the jars, leaving ¼-inch headspace. Wipe the rims clean and set the lids on the mouths of the jars. Twist on the rings.
Using a jar lifter, gently lower the jars into the pots. When the water returns to a boil, decrease the heat to an active simmer, and process the jars for 10 minutes.
Transfer the jars from the pot and let sit for at least 6 hours, until cool enough to handle. Check to be sure the jars have sealed. Store the sealed jam for 6 months to 2 years. Once open, store in the refrigerator for up to 3 months.