Wart Lichen: The Tiny Garden Guardian You Never Knew You Had
Have you ever noticed those small, grayish patches on your garden walls, concrete steps, or stone borders and wondered what they were? Meet the wart lichen (Verrucaria submuralis), a fascinating little organism that might already be calling your garden home. Don’t let the name fool you – this isn’t actually a plant at all, but rather a remarkable partnership between fungi and algae that creates one of nature’s most resilient life forms.
What Exactly Is Wart Lichen?
Wart lichen is a crustal lichen, which means it forms thin, crusty patches that seem almost painted onto surfaces. This native North American species gets its common name from its slightly warty, bumpy texture when viewed up close. The grayish-green to brownish patches you see are actually a living partnership where fungi provide structure and protection while algae produce food through photosynthesis – talk about teamwork!
Where You’ll Find It
Verrucaria submuralis is widespread across North America, thriving in areas with good air quality. This lichen has a particular fondness for calcareous surfaces – think limestone walls, concrete sidewalks, mortar between bricks, and alkaline rocks. If you have stone retaining walls or concrete garden borders, there’s a good chance you’ll spot these little patches making themselves at home.
Is It Good for Your Garden?
Here’s where wart lichen becomes genuinely exciting for gardeners: it’s actually an excellent indicator of environmental health! The presence of this lichen in your garden is a positive sign that suggests:
- Your air quality is good (lichens are sensitive to pollution)
- Your garden environment is relatively stable
- You have suitable habitat for other beneficial organisms
While wart lichen won’t attract pollinators like flowering plants do, it contributes to your garden’s ecosystem in subtle but important ways. It helps break down rock surfaces over time, contributing to soil formation, and provides microscopic habitat for tiny creatures.
How to Identify Wart Lichen
Spotting Verrucaria submuralis is easier than you might think once you know what to look for:
- Appearance: Thin, crusty patches that look almost like they’re painted on the surface
- Color: Grayish-green when moist, often appearing more brownish or gray when dry
- Texture: Slightly bumpy or warty surface (hence the name)
- Location: On concrete, stone walls, mortar, and alkaline rock surfaces
- Size: Patches can range from tiny spots to several inches across
Should You Encourage It?
The wonderful thing about wart lichen is that you don’t need to do anything special to encourage it – if conditions are right, it will find you! This lichen establishes naturally and actually prefers to be left alone. Trying to remove it isn’t necessary and might indicate that you’re dealing with beneficial growth rather than something problematic.
However, if you’re working with new stone or concrete installations in your garden, be patient. It can take several years for lichens to naturally colonize new surfaces. The appearance of wart lichen on your garden structures is actually a sign that your outdoor space is maturing into a healthy, balanced ecosystem.
Living Alongside Your Lichen Neighbors
Rather than thinking of wart lichen as something to manage, consider it a quiet garden companion. It won’t compete with your plants, doesn’t require water or fertilizer, and actually adds a touch of natural character to stone and concrete surfaces. Many gardeners find that the subtle presence of lichens gives their garden walls and borders a more established, naturalistic appearance.
Next time you’re strolling through your garden, take a moment to appreciate these remarkable little organisms. In their own quiet way, they’re contributing to the health and character of your outdoor space while serving as living proof that your garden air is clean enough to support these pollution-sensitive creatures.
