The hip forms after the bloom has withered, so if you want to harvest hips you must stop deadheading the roses in August.
When I was a little girl, my grandmother taught me to make green apple jelly. She also adapted her recipe to make jelly from the rose hips in the fall. It's pretty simple, and very tasty. Rose hips have from 10 to100 times more vitamin C than most natural products along with vitamins A, E, B-1, niacin, K and P along with calcium, phosphorous and iron.
PREPARATIONS
If you want to try this winter ritual, here's how to start.
Be very sure the roses haven't been sprayed with insecticide or dusted with sulfur. This is very important. You want clean, untainted rose hips for your jelly.
Watch the hips form and when they are the right color (or you are sure they are ripe), pick them off. Most rose hip recipes require a good amount of rose hips.
Have sterilized jelly jars ready.
Wash the hips and chop them (nowadays, I use a food processor). Since this is going to be a jelly (which will be strained any way) you don't need to remove the skin or pick out the seeds. Just don't puree the stuff until the seeds break up -- if broken, they add bitterness to the jelly.
(Some recipes call for apple pieces to provide extra juiciness, which reduces the quantity of hips needed but not the particular taste and aroma of the hips.)