Pipsissewa: A well-connected evergreen

Just about anywhere you walk in the Nature Park, you will likely run in to patches of Pipsissewa (Chimaphila umbellata). This small, evergreen shrub is less than a foot tall with glossy toothed leaves arranged in whorls around a short central stalk. In the summer, 4-8 pink flowers rise up on long slender stalks of their own and give off a fragrance that attracts pollinators.

The intricate and delicate flowers of Pipsissewa.

Also known as Prince’s Pine and in Ktunaxa as ʔa·kpi¢̕is ǂawu, this little shrub spreads vegetatively by sending out underground rhizomes that sprout new stalks. A large patch of Pipsissewa could actually be just one individual organism that has spread underground.

This patch of Pipsissewa above Duck Pond Trail could be one individual.

Researchers have measured rhizomes from a single patch totalling over 180 feet. It is not clear how long these patches can live, but researchers have estimated that a single cloned patch could be up to 90 years old.

These white underground stems connect individual stalks of Pipsissewa.

Pipsissewa is a mixotrophic plant. This means that it can use the chlorophyll in its green leaves to fix carbon from the atmosphere but it also gains nutrients through a mycorrhizal association with fungi in the soil. The interconnectedness of many trees and shrubs through links with fungi in the soil is an amazing and currently much-studied aspect of ecosystems. The Kimberley Nature Park is a big network of plants and fungi that connect underground and transfer various nutrients between species. Fungi in the soil develop special structures that either surround or penetrate root hairs of plants. Carbon, nitrogen, water and other nutrients are shared back and forth between them. The whole system is made healthier because of this cooperation.

In the case of Pipsissewa, researchers have identified a dozen different fungal species that connect with its root hairs, some of which also connect with trees and other shrubs. When Pipsissewa plants are growing in a very shaded part of the forest, this fungal connection becomes very important.

Pipsissewa flowers, when fertilized, mature into small brown capsules which contain thousands of “dust” seeds. There may be as many as 7,800 seeds in one capsule.

The mature seed-containing capsules of Pipsissewa.

These seeds are evolved to be extremely light and can be carried by gentle breezes. But their reduced weight also means they carry a reduced store of nutrients that would normally help them start their growth when they germinate. Instead, they rely on fungi in the soil to give them what they need to grow. A seed falling on the ground needs to come in contact with an appropriate strand of fungal mycorrhiza in order to germinate. It is fortunate that forest soils are full of fungal mycorrhiza.

Dust seeds of Pipsissewa beside a grain of rice for comparison.

The next time you are out in the Park and notice these pretty little plants, consider the connections they have to the rest of the forest.