Black raspberries (Rubus occidentalis), are native to the northeastern United States.
If you are on the bicycle paths of Northampton in the next few days, look for ripe black raspberries along the paths. The plants grow wild along embankments in swampy areas. Some are close to people's homes, and have clearly been picked over, but others, far from frugal homemakers with their bowls and pans, are still full of ripe berries, begging to be tasted. Bring a plastic quart container with a lid to protect your berries on the ride home.
Pick only the blackest berries. Wash them first, then eat them fresh, or freeze them. Fresh or frozen, the berries can be mashed and then pushed through a sieve until as much of the liquid as possible is extracted, or put through a food mill to remove the many tiny, hard seeds for a smooth sauce, syrup, or jelly. Raspberry puree that has been filtered of its seeds is perfect for use on or in cheesecake, ice cream, sorbet, or soda.
To make black raspberry soda:
In a glass, mix a quarter cup of the puree with a tablespoon of sugar and the juice of half a lime. Add sparkling water to within a couple inches of the top of the glass, and add ice. Garnish with a lime wedge or sprig of mint.