Wednesday, August 11, 2010


Blue Jay Barrens primarily provides a dry environment, so there are limited opportunities for wetland plants to become established. The Arrowhead is one of the few wetland species that has found a place for itself here.

Arrowhead has established several small colonies in the silty deposition areas along the creek. These are unstable areas that can change radically during a flood. Colonies tend to flourish for a few years and then disappear. New colonies appear at about the same rate as disappearances, so the overall population remains fairly stable. This colony is on the inside of a 180 degree bend. The creek enters from the lower left of the photo and exits in the upper left.

This colony may enjoy a greater longevity than the others. A fallen tree across the creek is enough of an obstruction to cause the flood water to flow across the point to rejoin the creek. This reduces the amount of water going around the curve and makes it a more stable site.

A new channel is beginning to form where the water re-enters the creek. Eventually, the creek will follow this new route and by-pass the curve all together.

The Arrowhead at Blue Jay Barrens is the Midwestern Arrowhead, Sagittaria brevirostra. This is one of those species that has a qualifier at the end of the description cautioning that it may be hard to distinguish from some similar species. This species does have considerable variability between plants, but the characteristics clearly fall into the range of brevirostra.

As the flowers fade from the spike, they are replaced by a globular cluster of flat, dry fruits called achenes. When ripe, the balls will fall apart and the seeds will be spread along the entire length of the creek.

Each point of the cluster represents an individual achene. The shape of the point is another characteristic used in the identification of this plant.

I’m encouraged by the number of small plants growing at this site. Small plants are indicators of an expanding population and that indicates a stable or growing silt deposit. When flood water begins to erode the silt bar, the shallow rooted young plants are the first to go. Older plants can persist for years and can produce seed to rebuild the colony if the erosion process should abate.


  1. I have arrowheads in my patio pond- they look similar to these, but are a bit different. I haven't seen a flower yet- hopefully something to look forward to. Great to see wetland plants expanding their range.

  2. Thanks for visiting, Mike. Arrowheads are really neat plants. I don't know what species you have out your way, but I hope you have one that will bloom in your patio pond.