Fauna
Plant

Pellitory-of-the-wall

Parietaria judaica

Also known as Spreading Pellitory, Asthma Weed, Lichwort, Sticky Weed

Pellitory-of-the-wall thrives in vertical crevices, old brickwork, and rocky urban habitats, anchoring itself where few other plants can survive. Its reddish stems bear hairy, oval leaves and inconspicuous greenish flowers that release vast clouds of wind-borne pollen. While recognized as a primary trigger for urban allergies in Mediterranean climates, it provides vital habitat and host foliage for specialized insects.

Urban WeedPerennialAllergen Risk
Pellitory-of-the-wall reference
(c) Elizabete Marchante, some rights reserved (CC BY), uploaded by Elizabete Marchante · cc-by
—observations
—countries
—peak records
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Key facts
Diet & preyAutotrophic (Photosynthesis)
Predators
  • Red Admiral Caterpillar
  • Snails
  • Slugs
ThreatsHerbicides, urban wall repair, masonry repointing
HabitatsStone walls, masonry crevices, pavements, rocky slopes, waste ground
Life spanPerennial (5–10 years)
Classification
  1. OrderRosales
  2. FamilyUrticaceae
  3. GenusParietaria
  4. SpeciesParietaria judaica
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Produces abundant airborne pollen that triggers severe hay fever and asthma; avoid close exposure if sensitive.
Why it is dangerous
Produces potent airborne pollen containing proteins that induce severe allergic rhinitis, conjunctivitis, and asthma.
How to recognize a risky encounter
Look for dense bushy mats with reddish hairy stems and tiny green flower clusters emerging from wall cracks.
What to do
Keep distance during peak blooming periods in warm months and do not pull plants by hand if prone to pollen allergies.
Responsible observation
  • Pollen Awareness: Avoid shaking or disturbing flowering clumps between spring and autumn if sensitive to airborne allergens.
  • Habitat Spotting: Look for lush bushy clumps sprouting directly out of vertical mortar joints and shady stone walls.
  • Identification Detail: Check for sticky hooked hairs on stems and leaves that easily cling to clothing.
Related species
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