Arrowhead Rescue

Before I propped it up on a convenient gravel bar, this young Arrowhead plant, Sagittaria brevirostra, was riding the creek currents on its way out of Blue Jay Barrens.  I’ve never before collected anything but seed for my propagation studies, but I thought, since it was leaving the property on its own, I might has well transfer it to a pot and watch its development.

Survival of the specimen should be easy.  The plant already possessed a healthy root system and a tuber packed full of energy.

I find the Arrowheads typically growing in mud banks developed on the insides of creek curves.  These mud banks are transient, growing and shrinking at the whim of an unpredictable flood cycle.  Sometimes, entire colonies of the plants are lost to a particularly violent flood.  I imagine those plants travel downstream with the possibility of colonizing a new mud bank.

The plant was moved from the creek to a pot on May 20, 2015.  Two months later, the pot was filled to capacity with plants.  I emptied the pot and began to separate the plants in preparation for repotting.

Each new plant was equipped with a profusion of roots and rhizomes.  It was easy to see that a single plant finding its way to a suitable site could quickly produce a large population.

What once filled a single pot, seemed still crowded when spread into three.

The original rescued plant was the only one of the bunch that was not growing tall and straight.  When removed from the original pot, its roots were still near the surface of the soil as originally planted.  The rest of the plants arose from rhizomes that had penetrated to the bottom of the pot.

By early August, the plants were flowering.

This Arrowhead species produces individual male and female flowers.  A small fly visits this male flower.  Small bees and flies were the most frequent visitors to the arrowhead flowers.

The female flower.

The individual fruits are clustered to form a spiked ball.  Each fruit, achene, bears a single seed.

Shape of the mature achene is one characteristic used in the identification of species within the genus Sagittaria.  Achene shape can vary greatly among different plants of the same species and also within a single flower, so one should never be comfortable with an identification based on a single achene.

This species has little tolerance for the cold and was zapped by the first hard frost.  Plants in the creek grow where the creek water keeps the soil at a temperature above freezing.

I didn’t think the plants would survive their pots freezing solid, so they will spend the winter buried in a leaf filled pit with a loose covering of boards.  It would take a record cold year for freezing temperatures to reach the pots stored here.

Arrowhead

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.