Easy Rhubarb Jam

Prepare the jars

1. Sterilize the jars and lids for canning by boiling them in a large pot of water. Place a small plate in the freezer.

Make the jam

1. In a large bowl, place the rhubarb, sugar, water, lemon juice, spent lemon halves, and lemon seeds (which provide the necessary pectin for thickening), and let rest on the counter for 1 hour. (If you want to make your life easier later on, tuck the lemon seeds in a tea ball or tie them in cheesecloth to make for simple retrieval.)
2. After 1 hour, dump the rhubarb mixture into a pot and bring to a boil over medium-high heat. Continue to cook, stirring the jam constantly, for about 15 minutes. Skim any foam from the surface of the jam as it arises.
3. After 15 minutes, reduce the heat to medium to keep the jam at a constant simmer, stirring frequently, to make sure the jam isn't scorched at the bottom of the pot.
4. After a total of 30 minutes simmering, check to see if your jam has set by taking the plate from the freezer and dolloping a small spoonful of the jam on the plate. The jam is set when it holds its shape on the cool plate rather than turning into a blob. If it seems a little runny, continue cooking over medium-low heat until set.
5. Remove the lemon halves and seed bag and toss them in the compost or trash.

Store the jam

1. If using the rhubarb jam within a week or two, ladle the jam into the sterilized jars, filling them to the bottom-most ring at the top of the jar. Gently tap the bottom of each jar on the counter to release any air bubbles. Using a damp clean towel, wipe the rims of the jars and secure the lids and rings. Place in the refrigerator and use to your heart's content.
2. If canning the rhubarb jam and using it over the next year, ladle the jam into the sterilized jars, filling them to the bottom-most ring at the top of the jar. Gently tap the bottom of each jar on the counter to release any air bubbles. Using a damp clean towel, wipe the rims of the jars and secure the lids and rings. Continue with the following steps.
3. Process the jars of rhubarb jam in a water bath for 5 minutes if using pint jars, 10 minutes if using quart jars. [For more information on canning, see our handy Guide to Canning below.] Use tongs to remove the jars from the pot and let them cool on the counter.
4. When the jam is room temperature, remove the metal rings, check for proper seals, and label with the date and contents. Store in a cool, dark pantry for up to 1 year.