Marrubium supinum: characteristics, taxonomy, habitat and identification keys in the Iberian Peninsula
Marrubium supinum, also known by popular names such as horehound, marrubillo, manrubio, marjoram o snowy horehound, is a species of perennial herbaceous plant belonging to the family LamiaceaeThis species stands out for its extraordinary capacity for resistance and adaptation to different types of terrain, from degraded environments to roadsides and mountainous areas. Of predominantly Mediterranean origin, the Marrubium supinum It is one of the most characteristic components of the flora of the eastern half of the Iberian Peninsula, although it is also found less frequently in mountainous areas of North Africa, such as Morocco, Algeria and Tunisia.
Below you will find a complete and updated description of its morphological characteristics, the habitat, distribution, taxonomy, etymology, traditional uses and key aspects to differentiate it from other species of the genus. This comprehensive information will allow us to recognize the Marrubium supinum in their natural environment and understand their ecological and cultural relevance.
What is Marrubium supinum and what are its unique features?
Marrubium supinum is a perennial succulent plant, that is, it persists year after year and, in adult specimens, its base shows some lignification. This plant was described by the naturalist Carl Linnaeus in his influential work Species Plantarum. The gender Marrubium be part of the family Lamiaceae, previously known as Labiatae, which groups together species with numerous traditional applications and aromatic properties.
In the case of Marrubium supinum, its hardiness is one of its most notable traits. It can grow in a wide variety of soils, from the poorest and rockiest to those with a high organic matter content, and it tolerates both intense sunlight and seasonal drought conditions. Its importance in the Iberian and North African flora is reflected in the wealth of common names it receives:
- Bitter horehound
- Mountain horehound
- Sierra horehound
- manrubio
- Spanish horehound
- Snowy horehound
- Spanish Manrubio
- Snowy horehound
- Branched horehound
- mastranzo
Thanks to its rusticity and tolerance, the Marrubium supinum It is common in roadsides, rocky ground, degraded soils, nitrified lands and other uncultivated spaces, showing an incredible capacity to adapt to both stony and poor soils and more fertile areas. It can be found from sea level to altitudes close to 2500 meters.
Habitat, distribution and flowering of Marrubium supinum
Marrubium supinum shows preference for open terrain, sunny and well-drained. It thrives in nitrified soils, both in rural areas and in degraded pine forest clearings, slopes, abandoned crop fields, pastures, edges of forest tracks, and even areas where livestock are grazed or where organic matter is enriched. Its presence is significant in mountainous areas of the central and southern Iberian Peninsula, although it can also be found at lower elevations, provided light and substrate conditions are favorable.
In North Africa, although much less widespread, it can be found in similar environments: open, often stony spaces, sunny slopes and hillsides, or nutrient-poor soils. This adaptability has allowed it to persist in highly diverse ecosystems.
The flowering period of the Marrubium supinum Its flowering period extends from spring to well into summer. Its flowers can generally be seen from April or May until August, depending on the altitude and climatic conditions of the area. This extended flowering period makes it an important species for the insect pollination in semi-arid and mountainous areas.
A particularly interesting fact is that, in those areas where the Marrubium supinum lives with Marrubium vulgaris, both species can hybridize naturally, giving rise to hybrids with intermediate characteristics.
Morphological description of Marrubium supinum
El Marrubium supinum is a perennial herbaceous and suffruticosa plant, which means that it is capable of living for several years and has a woody base, especially in adult specimens. The height of the plant can vary considerably, from about 15 until reaching 80 centimeters, although in most cases their size usually ranges between 20 and 70 cm.
The stems have a quadrangular section (a key characteristic in the Lamiaceae family) and are densely tomentose, that is, covered in silky, white hairs, giving them a woolly appearance. This hairiness is especially evident in specimens from sunny, dry areas, an adaptation that allows them to reduce transpiration and protect themselves from solar radiation.
Leaves They are simple, opposite, and stand out for their circular or ovate shape, sometimes slightly suborbicular. The edges may be crenate or weakly lobed, and the texture is noticeably hairy on both sides, except on the veins on the upper surface and especially on the underside, where the hairs are very evident. The petiole is long (2 to 4 cm), especially in the lower leaves of the stem, and tapers off towards the upper leaves. Its color is usually grayish green, tinged with whitish reflections of the hairiness.
The inflorescences They are arranged in globose whorls 2 to 3 cm in diameter, located in the axils of the upper leaves. Each whorl contains between 16 and 26 flowers, giving the plant a dense and striking appearance during flowering. bracts They accompany the flowers and can measure between 2,5 and 3 cm; they are usually elliptical, arched downwards, and can be sessile or with a short petiole. For their part, the bracteoles (smaller than the bracts) measure between 6 and 10 mm, are linear, thin, very sharp, almost prickly and curved upwards, and are covered with hairs.
The flowers of Marrubium supinum They have a tubular calyx, generally centimetre-sized, with five equal, linear, erect or slightly curved outward teeth, and also very hairy. The calyx is furrowed by ten veins and protected by long, silky hairs, giving it a velvety appearance.
La corolla It can be cream, purple, pink or even lilac depending on local conditions and is formed by two unequal lips: the upper one (4 to 6 mm) is bifid for more than a third of its length, while the lower one has a large central lobe 4 to 6 mm long and 3 to 5 mm wide, orbicular in shape and somewhat emarginate; on both sides there are two much smaller lobes. This morphology is useful to differentiate the M. supinum of closely related species, especially the M. vulgare, whose flowers are usually white and have a calyx with 6-12 hooked teeth.
The fruits of the Marrubium supinum are tetranuculae, that is, when ripe, they divide into four small units called mericarps. These mericarps measure 2 to 3 mm and have a trigonous shape (with three sides) and a slightly granular surface, especially on the two inner or smaller sides. Their color varies from dark brown to blackish.
The combination of the woody base, the density of whitish hairs, the quadrangular section of the stem, the morphology of its leaves and the characteristics of its inflorescences and flowers constitute the main keys to the accurate identification of this species in the field.
Etymology and synonymy
The generic name Marrubium It probably goes back to the Hebrew “Mar” (bitter) and “Rub” (juice), in clear reference to bitter taste from the plant's juice. This etymology fully corresponds to the sensory experience of chewing its leaves or stems.
El Marrubium supinum It has received various scientific names over time. Its botanical synonyms include Marrubium sericeum Boiss., Marrubium incanum Desr. y Marrubium supinum var. boissieri RouyIts classification and taxonomy have become clearer as morphological and genetic studies of the family have been perfected. Lamiaceae.
Taxonomy and classification of Marrubium supinum
La taxonomy of Marrubium supinum reflects its belonging to a group of plants perfectly adapted to Mediterranean and steppe environments. The genus Marrubium includes around 50 species accepted, although up to 180 names have been described. Within the Iberian Peninsula, only three species and one hybrid are present: M. Alysson, M. supinum, M. vulgare and the hybrid M. supinum × M. vulgare. The Marrubium supinum It is distinguished by having a calyx with five teeth (not hooked) and a cream or purple corolla, as opposed to the characteristics of its relatives.
- Kingdom: Plant
- Subkingdom: Tracheobionta
- Division: Magnoliophyta
- Class: Magnoliopside
- Subclass: Asteridae
- Order: lamiales
- Family: Lamiaceae
- Subfamily: Lamioideae
- Tribe: Marrubieae
- Gender: Marrubium
- Species: Marrubium supinum
Differences with other species of the genus Marrubium
In the Iberian Peninsula, Marrubium supinum can be confused with Marrubium vulgare and the Marrubium alyssonWhen differentiating them, it is essential to observe the number and shape of the calyx teeth, as well as the color of the corolla:
- Marrubium vulgare: calyx with 6-12 hooked teeth and whitish or cream corolla.
- Marrubium supinum: calyx with 5 erect or slightly curved teeth (not hooked), purple or whitish corolla.
- Marrubium alysson: calyx with rigid and patent teeth, purple corolla.
The dichotomous key therefore allows the precise identification of the Marrubium supinum when it is in bloom.
Curiosities and traditional uses
El Marrubium supinum It has attracted the attention of traditional botany, but also that of ethnobotany. Although its use in folk medicine is not as well documented as is the case with Marrubium vulgaris (better known as common horehound), it is known that species of this genus have been used for bitter infusions and home remedies, especially for its intense flavor and certain balsamic properties y digestive.
Some sources attribute to this plant applications very similar to those of Marrubium vulgaris, Although Marrubium supinum It is less common in gardens and agriculture due to its preference for wild soils and its bitter taste.
Ecological importance of Marrubium supinum
This species plays a key role in Mediterranean ecosystems where it lives, providing food and shelter to pollinating insects, especially bees and butterflies. Its resistance to drought conditions and its ability to colonize impoverished soils make it a pioneer plant, facilitating plant restoration in degraded areas and improving the local biodiversity.
The unique combination of morphological characteristics, its habitat diversity and its ability to natural hybridization make of Marrubium supinum A species of great botanical and ecological interest. Observing it during a walk through the mountains of the southeastern peninsula, its stony plains, or forest slopes is always an opportunity to study the adaptation and evolution of plants in the Mediterranean region.
