A real caper is the flower bud of a caper plant, Capparis spinosa, and its large seedpod is called a caper berry. The seedpods of nasturtiums look just like the caper plant's buds, and when pickled they taste remarkably similar. Nasturtiums usually don't start forming seedpods until late in the summer and you have to search for them. You'll find them attached to the stems underneath the foliage, where they develop in clusters of three. Pick only young pods that are still green and soft. When they mature, they turn yellowish and the seed inside the pod is very hard and unpalatable.