Wash and slice enough rhubarb to equal five cups. Prepare strawberries by removing the leaves and slicing in quarters.
Place rhubarb in an eight-quart Dutch oven and sprinkle with some of the sugar.
Add prepared strawberries and cover with sugar.
Add lemon zest and the juice from the lemon. Quarter the juiced lemon and add to the pot, along with the cinnamon, cardamom, and dried and ground orange peel (if using). Citrus fruits are naturally high in pectin and will make up for the lack of pectin in the strawberries and rhubarb.
Cover with the remaining sugar.
Place the lemon seeds inside a tea ball or soup bag and add to the pot. Why? Because lemon seeds are also loaded with pectin.
Place the pot over low heat, uncovered, allowing the sugar to melt slowly.
Once the sugar begins to liquefy, gently stir so that the fruit does not get scorched.
When the mixture begins to boil, adjust the heat to low-medium and allow the preserves to simmer. Skim the foam that forms on the surface.
Meanwhile, place the jars and lids in a large pot filled with enough water to fully submerge the jars. Boil for approximately ten minutes to sterilize.
After the preserves has simmered for 30 to 35 minutes, it should start to jell.
A quick way to test the jam's consistency is to take a few tablespoons of the jam and place it in the refrigerator for five minutes to ten minutes. If the jam does not jell, it needs to simmer further.
When you're satisfied with the texture, remove the lemon rinds and carefully pour the jam into the sterilized jars, leaving a ¼" space from the top of the jar. A canning funnel really helps with this step.
Wipe off the rims and sides of the jars with a damp washcloth, then screw the lids, but not too tightly, so that the air can escape. Process in the boiling water for an additional ten minutes.
Once the jars seal, tighten further and store in the panty up to a year.