Use of hemiparastic plants to increase species diversity

In a post two years ago, I showed that lousewort (Pedicularis lanceolata), a hemiparasitic plant, was infecting the sedge Carex trichocarpa and holding it in check. This sedge forms monospecific stands that are so dense that other species are not able to grow. Although it may be better to have the sedge than reed canary grass (another possibility in our wetland), it certainly reduces species diversity, as the upper photo shows.

This year this sedge-lousewort system has advanced and several other wetland species have now become established in areas that formerly had only sedge. The lower photo shows the result. Quite a contrast.



Species now present are cup plant, golden glow (Rudbeckia laciniata), mountain mint, blue vervain, and great blue lobelia.

The role of wood betony (Pedicularis canadensis) in increasing diversity in prairies has been well established, so it is not surprising that lousewort can have the same effect.

These hemiparastic plants have been called "keystone" species, whose very presence contributes to the diversity of life.

In prairie ecology wood betony keeps grasses in check, thus increasing the possibility for establishment of forbs. It now appears that lousewort can play the same role in wetland ecology.