Black bog-rush is important for other plants. It provides oxygen to its surroundings which is good ground ventilation. It also absorbs calcium, which it releases when the leaves die off. This is why it is favorable for other plants to germinate where black bog-rush grows. Black bog-rush grows in thick clusters and is easy to recognize by its dark flattened button-like 'flower' standing at the tip of its stem. Rabbits like to nibble on the leaves and it is a host plant for various moths and flies.