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Hemerochory (Ancient Greek ἥμερος, hemeros: 'tame, ennobled, cultivated, cultivated' and Greek χωρίς choris: separate, isolated), or anthropochory, Botanical Nerd Word: Anthropochory Toronto Botanical Garden. Retrieved 17 December 2023. Wandering Ecologies: Anthropochory as a Method of Restoration; Seed Dispersal in the Urban Landscape by Brittany Johnston. University of Technology Sydney. Retrieved 17 December 2023. is the escaped plant of cultivated plants or their seeds and cuttings, consciously or unconsciously, by humans into an area that they could not colonize through their natural mechanisms of spread, but are able to maintain themselves without specific human help in their new habitat. Potentials and Limitations of Ecosystem Analysis, Extinction and Naturalization of Plant Species p.261, edited by Ernst-Detlef Schulze, Helmut Zwölfer
Hemerochory is one of the main propagation mechanisms of a plant. Hemerochoric plants can both increase and decrease the biodiversity of a habitat. Harshberger, John William: The vegetation of the New Jersey pine-barrens, an ecologic investigation, Philadelphia: Christopher Sower Company, 1869-1929
In the last 400 to 500 years the spread has expanded through trade and military campaigns, through explorers and missionaries. The latter brought countless plants with them from their travels both out of an interest in , which were often included in the plant collections of princely courts, and for purely scientific purposes. In the context of botanical studies, the interest was often in the possible medicinal plant of these plants, but also in the expansion of botanical knowledge, or the plants were only used for collecting (herbaria).
Some ornamental plants also came to Europe because they promised a lucrative business. This applies, for example, to the camellias, one of which is also grown as a tea plant in Japan and China. While this species turned out to be not cultivable in Central Europe, people very quickly discovered the aesthetic appeal of the other camellia species as an ornamental plant. Botanical gardens played a major role in the acclimatization of such plants from distant habitats.Krystyna M. Urbanska: Populationsbiologie der Pflanzen. G. Fischer, Stuttgart 1992, ISBN 3-437-20481-5.
However, mainly are spread through agochory. Ballast water plays a major role in the agochoric spread of aquatic plants. Around the world, around ten billion tons of seawater and the organisms it contains are shipped in this way. Exporting countries in particular are affected by the spread of organisms through ballast water. The ships arrive at the ports with empty cargo hold, but fully pumped ballast tanks. In the draining of this ballast water, these ports receive thousands of cubic meters of seawater brimming with alien creatures now in a new environment. The seaweed Undaria pinnatifida, which is native to the Japanese coast, reached the coast via ballast water and has formed dense kelp forests along the coast since 1988, displacing the native flora and fauna. Caulerpa taxifolia is one of those plants that are often spread by ballast water. It is also spread by the fact that ships tear off parts of the algae with their anchors.
Australia was the first country to introduce a ballast water policy back in 1990 and is now the most determined to address this problem. Ships were asked not to take in ballast water in shallow and polluted bays and not to refuel with ballast water during the night, since then many that are otherwise on the seabed rise to the surface of the water. Ships should also exchange their ballast water 200 kilometers away from the coastal waters, so that on the one hand the offshore species are not introduced into the more sensitive coastal waters and, on the other hand, no inhabitants of the coastal zone are transported to other continents.Management of an invasive marine species: defining and testing the effectiveness of ballast-water management options using management strategy evaluation by Piers K. Dunstan and Nicholas J. Bax
Many of the old cultivated plants have spread around the world, primarily through emigrants from Europe. Grown for at least 4,000 years, wheat was introduced to America in the 16th century and Australia in the 19th century. Orange, lemons, apricots and peaches were originally native to China. They probably came via the Silk Road as early as the 3rd century BC. In Asia Minor and from there through the Ancient Rome to the Mediterranean. European settlers, in turn, used these species to grow fruit in suitable regions of America.
From the 16th century, ornamental plants were grown more and more. Species native to Europe were first introduced as . These include, for example, the gladioli, the ornamental onion, European bluebell, the snowdrop native to southeast Europe and the common clematis. Ornamental plants from more distant regions were added later. From East Asia in particular, a number of plants were introduced to Europe as exotic or for economic reasons.
Speirochoric plants are sown on human-prepared soil and are competitors of the . Plants that are considered to be archaeophytes, such as the poppy, native to the Mediterranean area, the real chamomile, the cornflower and field buttercup, spread through the seeds with the grain in Central Europe. In the meantime, the seeds are cleaned more thoroughly using modern methods and the cultivation is hardly contaminated by or other control techniques.
In spite of this, Cuscuta campestris, which is classified as a problematic weed in Australia, was accidentally imported into the country together with basil seeds in 1981, 1988 and 1990.
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