Vernal Pools, Part I

A small clump of white water cress (Rorippa nasturtium-aquaticum) plants removed from a vernal pool.


Individual water cress.


White water cress leaves.


Pulling invasive plants is often the price of admission:

On one section of the Sourland ridge are a series of vernal pools. Last week they were writhing with wood frogs. A couple spring peepers called out. This week, the peepers are making a racket, and the wood frogs have disappeared.

One of the pools had the beginnings of a white water cress infestation. I knew I wouldn't be back soon enough, so I tossed off my shoes and socks and delicately waded into the pool. The cress was easy to pull. The egg masses felt wonderfully warm as I carefully moved them aside to remove the cress.

White water cress can be fully or partially submersed. It grows in shallow waters. When crushed the leaves smell pungent, like nasturtiums. It will destroy vernal pools by creating a mass of plant material. It also infests shallow streams, ponds, and other shallow quiet waters. Its flowers is small, white and has 4 petals. Its bright green basal rosette overwinters. Plants can spread via seed or dislodging of the adult plant.

I've seen this weed in two other places in the Sourlands -
1. another documented vernal pool.
2. a pond made by damming up a section of Rock Brook tributary. The cress is upstream from the pond in both the brook and in the muddy area just before the pond deepens. It has also made its way past the dam.

In all cases, the white water cress will be removed easily by hand pulling. I hope to say "adios" to this plant in my neck of the woods.

Have you seen white water cress?