It is a perennial, herbaceous, suffrutescent, hemicryptophyte plant, which dies off in the winter, but regrows from the rootstock the following spring.

[10] Numerous erect to spreading stems grow from the crown of the root-stock in the spring,[22][23] these branch in a corymbose fashion.

It also contains (four) alkaloids, in relatively high concentration compared to the flowers of other species, among them the toxins harmalol and harmine.

[2] The seeds are colored dark brown[22] to blackish-brown,[2] slightly curved, triangular, about 2 mm (0.08 in) long with a muriculate surface.

[1][3] It is a common weed in Afghanistan,[citation needed] Iran,[6][36] parts of Israel,[37] eastern and central Anatolia (Turkey),[20] and Morocco.

[41] In Egypt it grows in the Sinai,[1][4][38] has been recorded from the east of the Eastern Desert,[42] and been rarely collected on the mid-west of the Mediterranean coast.

[38] In Europe it is native to Spain, Corsica (disputed), much of Russia, Serbia, Moldova, Ukraine (especially in Crimea), Romania (possibly introduced), Bulgaria, Greece (including Crete and the Cyclades), Cyprus, Turkey (Thrace) and southern Italy (including Sardinia, but not Sicily).

[24][25][38] On the Iberian Peninsula it is absent from Portugal and Andorra, but it is not uncommon in Spain, especially in the southeast, the Ebro depression, and the inland valleys of the Duero and Tajo, but it is rare in Andalusia (south) and it does not occur on the Balearic Islands and the Canary Islands, and in the west along the Portuguese border, Galicia, the northern coast, and the northern mountain ranges.

[26] It grows in drier parts of the northern half of India[28][29][38][44] but is possibly only native to the Kashmir and Ladakh regions.

[25] It was first planted in the United States in 1928 in New Mexico by a farmer wanting to manufacture a dye called "Turkish red" from its seeds.

[22] In Spain it can be found in abandoned fields, rubbish tips, stony slopes, along the verges of roads, ploughed and worked earth, as well as in disturbed, saline scrubland.

[26] Between 800 and 1300 metres (2600' to 4300') elevation on the sandstone slopes of the mountains around Petra, Jordan, there is an open Mediterranean steppe forest dominated by Juniperus phoenicea and Artemisia herba-alba together with occasional trees of Pistacia atlantica and Crataegus aronia with common shrubs being Thymelaea hirsuta, Ephedra campylopoda, Ononis natrix, Hammada salicornia and Anabasis articulata; when this habitat is further degraded (it is already degraded) by overgrazing P. harmala along with Noaea mucronata invade.

[52] A species of tiny, hairy beetle, Thamnurgus pegani, has been found inhabiting stems of P. harmala in Turkey and elsewhere.

When the aerial parts of the plant begin to die off in the autumn, the adult beetles retreat to overwinter in the soil underneath the root-crown, or in old larval tunnels in the dead stems; emerging in the spring (May in Turkey), the females bore small holes in the now shooting stems of the plant, in which they lay their eggs.

The infected plant tissue turns blackish and is then used by the adult beetles and their larvae as a food source, until they are ready to pupate within the stem tunnels.

[55] The 12th century Arab agriculturist Ibn al-'Awwam from Seville, Spain, wrote that the seeds were used in the baking of bread; the fumes being used to facilitate fermentation and help with the taste (he usually quotes older authors).

[56] By the mid-16th century, Dodoens relates how apothecaries sold the plant under the name harmel as a type of extra-strength rue.

[61] Later, in his Pinax Theatri Botanici of 1623, he attempts to sort the synonymy in all the previously published names by the botanists from earlier in history.

He cites this species as based on Bauhin's Pinax Theatri Botanici of 1623, and Stirpium Historiae Pemptades Sex of 1583 by Rembert Dodoens.

It was subsequently collected only once more, at least as recorded in the GBIF, in 1980 in Spain near the bank of the Ebro river approximately halfway downriver to the sea from Zaragosa.

[2] Pierre Edmond Boissier described it in 1867[29] and it has been recognised as growing in Iran,[29][75][76] Iraq,[29] Afghanistan,[29][75][76] Pakistan,[29][75][76] India,[29][75] Tajikistan,[75] and the northern Caucasus.

[75] In India it is found in Kashmir, Punjab, Haryana, Rajasthan, Uttar Pradesh, Gujarat, Maharashtra and Karnataka.

[29] It can be distinguished from the nominate form by having finer leaves with more narrow lobes, shorter sepals and broader-shaped seed capsules.

[citation needed] Since 2005, the possession of the seeds, the plant itself, and the alkaloids harmine and harmaline, which it contains, is illegal in France.

[22] In the United States, where it is not native, it is officially registered as a noxious weed or similar designation in Arizona, California, Colorado, Nevada, New Mexico and Oregon.

[83] Leaves and seeds are considered poisonous due to the β-carbolines such as: harmalol, harman harmaline, harmine, and quinazoline derivatives they contain.

[23] In Iran and neighbouring countries such as Turkey and Azerbaijan, dried capsules from the plant are strung and hung in homes or vehicles to protect against the evil eye.

[14] In Yemen, the Jewish custom of old was to bleach wheaten flour on Passover, in order to produce a clean and white unleavened bread.

Reportedly, the ancient Greeks used the powdered seeds to get rid of tapeworms and to treat recurring fevers (possibly malaria).

[57] Peganum harmala seeds have been used as a substitute for Banisteriopsis caapi in ayahuasca analogs, as they contain monoamine oxidase inhibitors that enable DMT to be orally active.