Boulder Lake orchid presentation 11.19.22

The Arrowhead Native Plant Explorers met on November 19 at the Boulder Lake Environmental Learning Center about 30 minutes north of Duluth. Zane welcomed us to the Center, which is a partnership between UMD, Minnesota Power, and St. Louis County set within an 18,000 acre management area.

Our speaker was Rubin Stenseng, who is both treasurer for the Explorers and a volunteer/explorer at Boulder Lake. We learned all about the 49 species of orchids in Minnesota, which range in height from just a few inches up to 40 inches tall, and in flower color from green to yellow to pink. All orchid flowers have 3 petals, one of which is modified into all sorts of odd shapes and is called a “lip.” And all orchids require a fungal partner living in the soil. In fact their seeds are so miniscule that they can’t germinate at all without the fungus providing nutrients. As they grow, an active trade develops, sugars from the orchids exchanged for nutrients from the fungus. Digging up orchids often results in the death of the fungus, and ultimately the orchid too.

Rubin described in detail the 15 species of orchids recorded so far at Boulder Lake, starting with the lady slippers. Two of Minnesota’s six lady slipper species have been found at Boulder, the stemless pink and the large yellow. In lady slippers the lip is an inflated pouch. Bees are drawn inside, but they find no nectar. The only exit at the top forces the frustrated bees to brush against sticky pollen balls.

Above: flowers (both orchids and non-orchids) with tiny, spore-like seeds

Rubin also described the two species of coral root orchids found at Boulder. These have little to no chlorophyll, and they rely completely on their fungal partner for survival. What the fungus receives in return is unknown. Many of our orchids are striking in appearance, including the gaudy purple fringed orchid and the downy rattlesnake plantains with its variegated leaves. Thanks to Rubin for such an in-depth discussion.

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