La Pellitory, also known as parietaria officinalis o Jewish parietaria, is a very common plant in walls, ruins and urban or semi-urban areas. Despite going unnoticed by many, it has a double aspect in relation to humans: on the one hand, it is highly appreciated for its traditional medicinal uses, and on the other hand, it is one of the most common allergens affecting thousands of people, particularly in the Mediterranean area and other urban areas in southern Europe.
In this article you will discover everything about the Pellitory: its botanical characteristics, habitat, how to recognize it, interesting facts, how it's grown and controlled, its many properties, and, especially, its powerful allergenic properties. If you want to know all the essential and advanced information about this plant, keep reading.
Botanical description and main characteristics
Parietaria is a herbaceous plant perennial plant of the Urticaceae family, which also includes stinging nettles. The most common scientific name for the allergenic species is Jewish parietaria, although it can also be found as parietaria officinalisAmong its many popular names are wall grass, glass grass, wall grass, snail grass, wall basil, and dead nettle.
- Level: It can reach between 30 and 80 cm, although it is most commonly seen between 30 and 60 cm tall. Its stems, generally decumbent and ascending, are thin, branched, and have a characteristic reddish color.
- Sheets: They are alternate, ovate-lanceolate or even orbicular-ovate in shape, with pubescence (soft, non-urticating hairs). They measure between 15 and 50 mm long and can easily adhere to clothing thanks to their fine, glandular hairs.
- Flowers: The flowers are inconspicuous, greenish or reddish-green, arranged in clusters in the leaf axils. These flowers have long yellow stamens and elastic filaments, which, upon light contact, release pollen into the air.
- Fruit: It is a small, shiny black achene, which contributes to rapid dispersal by wind.
A particularity of Parietaria is that it has a very branched and dense growth, which makes it easily recognizable in the cracks of walls, rocks and other urban habitats.
Origin, distribution and habitat
The origin of Parietaria is located in southern and western Europe, but thanks to its extraordinary capacity for adaptation Today it is distributed practically all over the world, especially in temperate and Mediterranean regions. To learn more about the variety and specific characteristics, we recommend reading the article on Jewish parietaria.
It abounds in:
- Ancient walls or stones from disused buildings
- Roadsides and highways
- Stony areas and debris
- Gardens and orchards as a weed that is difficult to eradicate
- Places rich in organic matter and especially nitrogen (near corrals, landfills, fertilized areas, ditches and crop borders)
It prefers shady areas and calcareous soils that retain moisture, although it can survive in poor substrates and with little competition from other plants.
In Spain, Parietaria is found especially in Andalusia (with extremely high pollen levels in cities and surrounding areas), the Catalan coast, Galicia, and the northern region. It has also colonized regions as diverse as California, Australia, and the Canary Islands, demonstrating its robustness and adaptability.
Detailed identification and taxonomy
- Kingdom: Plant
- Division: tracheophyta
- Class: Magnoliopside
- Order: Rosales
- Family: Urticaceae.
- Gender: Pellitory
- Featured species: Parietaria judaica L., Parietaria officinalis L.
The epithet "Parietaria" comes from Latin paries, which means wall, due to its tendency to grow on old walls and cracks in buildings. There are several subspecies (such as P. judaica subsp. afghanica, persica, speluncarum…), although in the Iberian Peninsula and Mediterranean area the prevailing Jewish parietariaTo learn more about specific care and characteristics, you can consult our article dedicated to rock plants and their care.
Growth and reproduction habits
Parietaria is a plant perennial but can behave as an annual in cold climates. It reproduces:
- By seeds: Abundant production of viable seeds that germinate quickly if they find suitable conditions.
- By cuttings: It is possible to propagate it vegetatively from stem segments.
It has great ease in colonizing spaces with little plant competition, such as walls or urban soils, and behaves as a chamephyte (its replacement buds are close to the ground, allowing it to survive short mowings or sudden changes in temperature).
How to grow, control and eliminate Parietaria
In gardening and agriculture, Parietaria can be both a resistant weed as a plant of medicinal value. Growing it intentionally is simple, but in most cases, the key is knowing how to prevent it from persisting in orchards and gardens.
- Sowing: Propagation from seed has a high success rate, especially in protected seedbeds where humidity can be controlled and weeds eliminated. If sowing directly into the ground, it is essential to eliminate other competing plants during the initial planting.
- Cuttings: For commercial or industrial purposes (due to its medicinal applications), it is ideal to use cuttings from vigorous specimens.
- Control: Regular weeding, manual uprooting in spring, and avoiding leaving bare ground or walls unmaintained helps limit their spread.
- Elimination: Organic methods (mulching, using mulches, competing with other ground cover species) are preferable to chemical methods in domestic environments. Manual removal should include roots to prevent regrowth.
Because of its ability to re-sprout and its low competition when surrounded by other species, planting dense lawns or ground cover plants can help displace it.
Flowering season and periods of greatest allergy risk
The Parietaria It produces pollen almost year-round, although the most intense flowering occurs in spring and late summer. This implies several critical periods for allergy sufferers:
- Spring (approximately March to July): Maximum pollen release, coinciding with rising temperatures.
- Late summer and autumn (September-October): It may experience a resurgence in pollination in urban areas due to the effect of rainfall and moisture retained on walls and debris.
The highest pollen concentrations are found in urban environments, as well as in areas near the coast. Pollination can be prolonged if temperatures are mild and the weather is humid.
Health impact: Parietaria allergy
- Most affected regions: Andalusia (especially Jaén, where it affects nearly 30% of the population), Galicia, and Catalonia.
- Age ranges: People between 15 and 30 years old, with women being slightly more affected.
- Urban and coastal areas: Higher incidence in populations near the sea compared to inland.
- Allergy period: It can extend from February to December in mild years.
Parietaria pollen is extremely fine and light, able to stay suspended in the air and travel great distances. This makes it one of the plants that cause allergies more persistent and worrying for allergists and patients, especially in spring and autumn.
Most common symptoms of Parietaria allergy
- Rhinoconjunctivitis (conjunctivitis and allergic rhinitis: sneezing, nasal congestion, watery eyes, itchy eyes)
- Allergic asthma in sensitive people
- Persistent effects if exposure is continuous (due to the constant presence of the allergen in the air)
The allergy to this plant is so powerful that, in areas such as the Mediterranean coast and southern Europe, it is considered the most important allergen behind the olive tree and the grasses.
Treatment and prevention of Parietaria allergy
Controlling pollen exposure is essential for allergy sufferers. The best strategies are summarized below:
- Avoid outdoor activities on days of maximum pollination, especially during the central hours
- Keep windows and doors closed during periods of high pollen
- Wear glasses and masks if it is essential to go out
- Wash clothes and hair after exposure
- Continue antihistamine treatment and, in severe cases, consider immunotherapy (allergy shots).
- Consult with allergists periodically, especially if persistent symptoms appear.
Specific vaccination against Parietaria pollen can significantly reduce symptoms after several years of treatment and improve the patient's quality of life.
Medicinal properties and other traditional uses
Beyond its role as an allergen, Parietaria has been widely used since ancient times in herbal medicine and folk medicine. It is notable for:
- Diuretic: It facilitates the elimination of fluids and has been used in infusions to treat retention, kidney stones, and urinary tract problems.
- Anti-inflammatory and healing: Applied in poultices on blows, burns, hemorrhoids and bruises, it helps to calm inflammation and regenerate tissues.
- Laxative y liver decongestant
- Expectorant and sudorific: Used to calm fever and as a purifier
- Cuisine: In the past, the tender leaves of Parietaria were added to soups and omelets, both raw and cooked, if they were well tolerated and there was no allergy.
- Cleaning: Its leaves were traditionally used to clean glass and copper containers, as they contain substances capable of softening dirt.
- Animal supplement: They were given to hens to ensure eggs with harder shells.
Among its active components are: Flavonoids (kaempferol), potassium nitrate salts, tannins, mucilages, sulfur compounds, and calcium oxalate. These give it its therapeutic properties, although any medical use should be done under professional supervision, as it is not without potential contraindications or adverse effects in sensitive individuals.
Curiosities, symbolism and additional tips
Parietaria is non-toxic to pets or people (except for allergy problems). There are no known major side effects other than allergic reactions, although it should never be consumed excessively or handled carelessly during pollination season.
- Symbolism: Because of its ability to grow on walls and ruins, Parietaria is often associated with resilience and resistance, surviving in adverse conditions and sprouting where other plants cannot survive.
- Gardening: Although it is considered a weed, it can be used as a ground cover plant in shaded areas if its spread is controlled.
- Pet Compatibility: There are no known toxic effects, but it is always advisable to avoid accidental consumption.
- Pruning and maintenance: It can be pruned after flowering to maintain its controlled shape or prevent the dispersal of seeds and pollen if grown in ornamental gardening.
Despite its reputation for causing allergies, Parietaria is a species steeped in resilience, history, and applications, making it much more than just an urban weed. By understanding its characteristics and learning how to manage it, it's possible to appreciate its interesting duality in the natural and human environments.
