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Phenology Report: Why are water-shield plants so slimy?

A water-shield plant blooms in St. Louis County on July 31, 2021. It is an aquatic plant with oval-shaped leaves lying on the water's surface. The flower is purple, with thick waxy petals.
Contributed
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iNaturalist user kayakmak
A water-shield plant blooms in St. Louis County on July 31, 2021.

KAXE Staff Phenologist John Latimer provides his weekly assessment of nature in Northern Minnesota. This is the week of July 30, 2024.

Staff phenologist and noted wordsmith John Latimer had a new vocabulary word for us this week: Mucilaginous, which means “covered in mucus.”

This was in reference to the water-shield, an aquatic plant that’s much nicer to look at than to touch. The underwater stems are covered in a snot-like jelly – this helps to protect the plant from getting eaten by aquatic insects and other herbivores.

Just because it's goopy doesn't mean it isn't valuable, though - the leaves and stems are edible, and the mucus itself is a valued material. It makes a great lubricant and is used to treat and prevent ulcers.

This weird little aquatic neighbor is in bloom, sending small, purple or pink flowers above the water’s surface. Since the water-shield emits an allelopathic chemical, they’re often found alone in clear water. They can kill nearby algae and aquatic plants and contribute to water clarity!

You can distinguish the water-shield from waterlilies by the shape of their leaves. The water-shield leaves are unbroken ovals, while yellow pondlilies have heart-shaped leaves and white waterlilies' leaves are mostly circular with a small notch.

An image compares the leaves and flowers of the water-shield, yellow pondlily, and white waterlily. The water-shield is labeled "1", and shows oval leaves with no notches and a purple flower. Labeled "2" is the yellow pondlily, which has heart-shaped leaves and a waxy yellow flower. Labeled "3" is the white water-lily, which has circular leaves with a notch cut to the center and a many-petaled white flower with a yellow center.
Charlie Mitchell
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Special to KAXE. Original photography by iNaturlist users kayakmak, carissab, and anya_doll.
An image compares the leaves and flowers of the water-shield, yellow pondlily, and white waterlily.

Topics

  • Introduction (0:00-0:28)
  • What to look for in August (0:28-6:53)
  • Tall blue lettuce (6:53-7:39)
  • Spotted jewelweed (aka touch-me-not) (7:39-10:44)
  • Asters (10:44-11:57, 16:58-18:46)
  • Goldenrods (11:57-13:11, 18:57-20:56)
  • Phenological calendar right on time (13:11-13:28)
  • Bladderwort (13:28-15:00)
  • Water-shields and waterlilies (15:00-16:41)
  • Hazelnuts (16:41-16:58)
  • Spreading dogbane (16:58-21:11)
  • Conclusion (21:11-23:15)

What have you seen out there? Let us know; email us at comments@kaxe.org or text us at 218-326-1234.

That does it for this week! For more phenology, subscribe to our Season Watch Newsletter or visit the Season Watch Facebook page.

Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR).

Stay Connected
Charlie Mitchell (she/they) joined KAXE in February of 2022. Charlie creates the Season Watch Newsletter, produces the Phenology Talkbacks show, coordinates the Phenology in the Classroom program, and writes nature-related stories for KAXE's website. Essentailly, Charlie is John Latimer's faithful sidekick and makes sure all of KAXE's nature/phenology programs find a second life online and in podcast form.<br/><br/><br/>With a background in ecology and evolutionary biology, Charlie enjoys learning a little bit about everything, whether it's plants, mushrooms, or the star-nosed mole. (Fun fact: Moles store fat in their tails, so they don't outgrow their tunnels every time conditions are good.)