Pick 4 cups of fresh nasturtium flowers, making sure to inspect them carefully for any insects, then rinse them briefly under cold water.
Place the flowers into a bowl and pour 4 cups of boiling water over them. Let the flowers steep for about 10 to 15 minutes, allowing the tea to fully infuse.
Once the tea is ready, strain it into a saucepan or jam pot. Stir in the lemon juice, which not only helps bring out the vibrant color of the jelly but also balances the sweetness and aids in setting the pectin. Additionally, the acidity from the lemon juice helps preserve the jelly, so it’s essential not to skip this step.
Bring the mixture to a boil and stir in the powdered pectin, ensuring it dissolves completely. Let the mixture boil for a full minute before adding the sugar. (Important: Do not add the sugar before the pectin or at the same time, as this will prevent the jelly from setting properly.)
After the pectin has dissolved, add the sugar, stirring until fully dissolved (refer to the sugar quantity note for preferences). Bring the mixture back to a rolling boil and let it boil for another minute before transferring it into sterilized jelly jars, leaving ¼ inch of headspace at the top.
If you're canning the jelly, process the jars in a water bath canner for 10 minutes (or 15 minutes if you're over 6,000 feet in elevation). If not canning, allow the jars to cool completely on the counter before refrigerating them (for up to a month) or freezing them (for up to 6 months).