Be sure the bushes from which you gather the rose hips were not sprayed.
Wash, pat dry, and pulse in a food processor until coarsely chopped:
Add to a nonreactive pan, along with:
Bring to a boil, then reduce to a simmer, cover, and cook until the rose hips are very soft, about 45 minutes. Line a sieve with several layers of cheesecloth and strain the liquid into a large measuring cup, pressing on the solids to extract all the liquid, then discarding the solids. Add enough:
to make 4 cups liquid in all. Transfer to a medium saucepan. Mix in a small bowl:
with a small quantity of the liquid and:
Bring the liquid to a simmer, take off the heat, and thoroughly whisk in the arrowroot mixture. Let cool, then chill in the refrigerator until ready to serve. Garnish with: