Why Sunburst Lichen Is Damaging to Headstones: Understanding the Damage & How to Prevent It

If you spend time documenting cemeteries, researching genealogy, or caring for historic graves, you’ve likely come across the bright yellow or orange blotches clinging to older headstones. This vivid growth, known as Sunburst Lichen ( Xanthoria parietina), might look quaint or “natural,” but beneath its sunny color is a serious threat.

Sunburst lichen is one of the most damaging biological growths found on gravestones, especially on older marble and limestone markers that are already soft from decades of weathering. Understanding why it forms, how it damages stone, and what to do about it is key to preserving historic cemeteries for future generations.

What Exactly Is Sunburst Lichen?

Sunburst lichen is a symbiotic organism made of both algae and fungi. It thrives in sunny environments, often forming on:

• Marble and limestone headstones

• Concrete markers

• Exposed stone foundations

• Older stones rich in calcium

Because it absorbs nutrients from the air and moisture from the stone itself, it’s especially common in cemeteries with acid rain, nearby agriculture, or high humidity.

How Sunburst Lichen Damages Gravestones?

Despite its harmless appearance, sunburst lichen can cause long-term, irreversible damage. Here’s how:

1. It chemically attacks the stone.

Sunburst lichen releases organic acids, including oxalic acid, which slowly dissolve the surface of marble, limestone, and other calcium-based stones. Over time, this can result in:

• Worn lettering

• Loss of carved detail

• Fading inscriptions

• Surface pitting

This chemical breakdown speeds up each year the lichen remains attached.

2. It holds moisture against the stone.

Lichen acts like a sponge, trapping moisture against the surface. Moisture is the greatest enemy of aging stone—it leads to:

• Cracking

• Flaking (spalling)

• Sugaring (granular disintegration)

• Biological growth, like algae and mold

This is especially dangerous in cold climates where freeze–thaw cycles push the stone apart from the inside.

3. Its structure penetrates the stone’s pores.

Sunburst lichen anchors itself with tiny root-like structures called rhizines. These creep deep into the microscopic pores of the stone. Removing lichen improperly, scraping, picking, or using harsh tools, can tear away the stone’s surface.

This is why so many older headstones show scars or missing chunks after someone tried to “clean” them aggressively.

4. It encourages other harmful growth.

Once sunburst lichen takes hold, it creates a moist, stable micro-environment that attracts:

• Moss

• Algae

• Fungi

• Black biological crusts

These accelerate erosion even further and make the stone harder to clean in the future.

Removing Sunburst Lichen Safely

Sunburst lichen shouldn’t be peeled, scraped, or wire-brushed off—doing so almost always damages the stone permanently.

Professionally recommended cleaning methods include:

• D/2 Biological Solution or Wet and Forget Outdoor - Widely used by the National Park Service and at Arlington National Cemetery.

• Soft natural-bristle brushes. No metal bristles—ever.

• Gentle water rinsing. Let the cleaner work for a while, reapply as needed, and let rainfall help.

• Multiple gentle cleanings instead of one harsh one. Slow, low-impact cleaning is always safer for historic stone.

  
  

Why This Matters for Genealogists and Cemetery Conservationists

Every bit of wear a headstone experiences is permanent. Once a carving is gone, it cannot be recovered.

Preventing lichen-related damage helps:

• Preserve family history

• Keep inscriptions readable for future generations

• Maintain the integrity of historic burial sites

• Protect culturally significant markers

Cemetery stones are irreplaceable historical artifacts—and sunburst lichen is one of the quietest but most persistent threats to them.

Trusted Resources for Further Reading

National Park Service – Preservation Brief 1: Cleaning Historic Stone https://www.nps.gov/tps/how-to-preserve/briefs/1-cleaning-water-repellent.htm

NCPTT (National Center for Preservation Technology & Training) Biological growth, stone deterioration, and cleaning research https://www.ncptt.nps.gov

Association for Gravestone Studies – Cemetery Conservation Guidelines https://www.gravestonestudies.org

D/2 Biological Solution – Scientific Studies & Conservator Use https://d2bio.com/research

Sunburst lichen may seem like a harmless spot of color on an old headstone, but its impact is far from benign. From chemical erosion to moisture retention and structural weakening, this bright organism can quietly destroy the very stones meant to preserve a person’s history. The good news is that with proper education, gentle cleaning techniques, and ongoing stewardship, we can slow or even halt this damage. By caring for these stones responsibly, we honor not just the past but the people whose stories deserve to remain visible for generations to come.

Until next time,

B!