Saturday, June 12, 2010

The ecology of yellow evening primrose in our backyard

There have been several great blog posts about pollinator plants and pollinator gardening, calling attention to both the good and the bad. (the latter post very articulately describes the problems with pollinator gardens). A while back I wrote about my disdain for the trend that was pollinator gardening. OK, disdain is way too strong, but you get the idea.

In honor of national pollinator week (June 21- 27), Kelly Senser from the National Wildlife Federation compiled favorite pollinator plants from gardeners from across the country (click here for the story). In this, I wrote about one of my favorite plants in our garden, the yellow evening primrose, (Oenethera flava). Tonight my wife and I watched as one of our yellow evening primroses opened- click here for a video of it happening (the action really picks up at 55 seconds).
Though the flower is gorgeous, large and showy, the real reason I like it so much is it offers a wonderful microcosm of wildlife gardening. In short, the primrose is moth pollinated, because it flowers at night. That is pretty cool in an of itself, and probably not that typical in the run of the mill pollinator garden. However, the neat thing is this is the host plant for a moth that does not feed on its nectar, since it is a daytime flyer: the five- line Sphinx moth, also known as a hummingbird moth. And where this whole story gets more interesting, and typifies the intricate plant/ insect relation ship is that even though the eggs and larvae are tied to the primrose, it needs something else to complete its life cycle- soft duff or sawdust.

In our yard it finds fresh, loose sawdust at the base of our aspen (Populus tremuloides)trees. The reason for this accumulation of saw dust is that the trees are invaded by the larvae of a long horned beetle- the aspen borer (Saperda calcarata). As the larvae tunnel through the aspen they force out sawdust that collects around the base. Also, as a defence, the aspen pushes sap out these wounds. The sap is a critical food source in the early spring for many species of butterflies that overwinter as adults like the mourning cloak or Lourquin's admiral (shown below feeding ion the sap of an aspen).
So, from this one example you can see how interesting and intimate the association of plants and pollinators are. Furthermore, you can also tell how unrelated some of these plants and animals are. Provide native species, and diverse assemblages and you will be rewarded with much more productive "pollinator" gardens than if you tried to plant a garden for pollinators.


  1. Wow -- complex! And if you'd only used pesticides you'd never have observed anything of this.
    People think I'm weird because I tolerate wasps flying in my back yard...

  2. Hi Chookie!
    Thanks for the comments- well said (about the pesticides)! David

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