Pick through the rosehips and remove any stems or debris. Give them a rinse to remove any dust. This is only necessary if you foraged your own rosehips, bought ones would have been cleaned already.
Place the rosehips in a medium saucepan and cover with the filtered water.
Bring to boil, the reduce the heat to low and simmer the rosehips, covered, for 1 1/2 hours.
Uncover the saucepan and simmer the rosehips for another 30 minutes, uncovered, until the liquid is reduced by half.
Strain the mixture through a fine sieve. Measure the liquid and stir in an equal amount of honey or sugar until dissolved.
While the liquid is still warm, stir in the honey or sugar until dissolved.
Pour your syrup into a clean jar or bottle (I used an old cod liver oil bottle for this purpose), label and store in the fridge.
This syrup will keep in the fridge for several months. It is delicious added to teas (especially to black tea), drizzled over pancakes and waffles, or used to sweeten smoothies or porridge.