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 the remaining sugar.
Add lemon zest and juice of one lemon. Quarter the juiced lemon and add to the pot, along with the cinnamon, cardamom, and dried and ground orange peel (if using). Cover with the remaining sugar.
Place the lemon seeds inside of a tea ball or soup bag and add to the pot. 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 with a spoon.
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 to ten minutes. If the jam does not jell, it needs to simmer further.
Meanwhile, place the jars into a large pot filled with enough water to fully submerge the jars. Boil for approximately ten minutes to sterilize.
When you're satisfied with the texture of the jam, remove the jars from the hot water and add the lids and rings. Remove the lemon rinds and carefully pour the hot jam into the sterilized jars, leaving a ¼ inch headspace.
Wipe off the rims and sides of the jars with a damp washcloth or paper towel. Screw the lids on hand tight and place the jars upright into the hot water. Process for an additional ten minutes.
Remove jars and place on a rack or a dish towel. Once the jars seal, tighten the lids and store in the pantry for up to a year.