Needlestack

That's looking for a needle in a needlestack.

Unless their flag of a flower is waving, finding such plants is like finding a needle in a needlestack.

In those decades of European peace and unchallenged British ascendancy, this small number of ships was enough to keep watch on the French ports and the major sea routes of the world, but not to hunt for needles in needlestacks and make all slavers and pirates quake with fear.