Archaeophytes

Archaeophytes are non-native (alien) taxa that were introduced by humans, either intentionally or unintentionally, and became naturalised in Britain and Ireland between the start of the Neolithic period and AD1500. Most were introduced by early farmers mainly in the Late Bronze Age, Iron Age, Roman or Medieval periods. Many originated as contaminants of crops or as escapes from gardens where they were grown for culinary or medicinal uses.

The rediscovery of the New World around AD1500 brought about radical changes in human demography, agriculture, trade and industry. It therefore marks an appropriate date to differentiate between ancient and modern introductions; those introduced before AD1500 were usually associated with food production whereas those that came after (neophytes) are mainly garden ornamentals and trees used for forestry.

Although the concept of archaeophytes has a long history in Europe, Preston et al. (2004) were the first workers to carry out a critical assessment of those present in Britain and Ireland. They used the following six criteria to identify probable archaeophytes:

1. A lack of fossil evidence before the Neolithic period
2. A preference for man-made habitats
3. Documentary evidence of occurrence in the wild before AD1700
4. Stable ranges since AD1700 or an increase/decline in response to environmental changes but not having expanded rapidly in new habitats
5. An uncertain native range in Europe
6. Likely to have also spread to ‘neo-Europe’ (Australia, New Zealand, North America)

Preston et al. (2004) produced a list of 157 probable archaeophytes including 150 species, 4 subspecies and 3 hybrids. They also listed a further 30 species which were certainly being grown in Britain before AD1500 that are rarely or never naturalised i.e. mainly occurring as crop relics and casuals. In addition, they included a list of 76 species regarded as doubtfully native in Britain but as an archaeophyte or probable archaeophyte elsewhere in Europe. They concluded that “These species are of particular interest as they may contain further taxa which should be considered as archaeophytes in Britain.”

Williamson et al. (2008) enumerate the numbers of archaeophytes included in Preston et al. (2004) that occur in Ireland either as archaeophytes (96 species) or casuals (30 species).

In their list of archaeophytes in Britain and Ireland, Stace & Crawley (2015) used a broader definition including an additional 45 taxa including the 30 species grown in Medieval gardens listed by Preston et al. (2004), 11 infraspecific taxa, 2 trees (walnut Juglans regia, pear Pyrus pyraster), Primitive Wheats Triticum spp. and Grape Vitis vinifera. In comparison to Preston et al. (2004) they differentiate three sub-groups of archaeophytes:

1. Denizen: having the appearance of being native (i.e. fully naturalised) but with some suspicion of having been originally introduced, e.g. ground elder Aegopodium podagraria.  There are 87 species in this category.
2. Colonist: almost exclusively confined to disturbed, anthropogenic habitats (cultivated land, roadsides or habitations), e.g. corncockle Agrostemma githago. There are 65 species in this category.
3. Cultivated: crops or their derivatives that escape or persist, e.g. horseradish Armoracia rusticana. There are 45 species in this category.

It should be noted that many archaeophytes declined dramatically in Britain during the twentieth century. These includes several arable species that are now extinct (lamb's succory Arnoseris minima, stiking hawk's-beard Crepis foetida, small bur-parsley Caucalis platycarpos, narrow-leaved cudweed Filago gallica, downy hemp-nettle Galeopsis segetum, violet horned-poppy Roemeria hybrida) or nearly so (corn cleavers Galium tricornutum, darnel Lolium temulentum) due to improved seed cleaning and increased use of herbicides. Several more are extinct in arable habitats but survive elsewhere as casuals due to deliberate sowing in ‘wildflower mixtures’ (e.g. corncockle Agrostemma githago, thorow-wax Buplureum rotundifolium, cornflower Centaurea cyanus). As pointed out by Preston et al. (2004) these are best treated as neophyte occurrences.

The table below includes the list of archaeophytes for Britain and Ireland produced by Preston et al. (2004) and the update by Stace & Crawley (2015) to include cultivated species introduced before 1500. It also includes the list of archaeophytes for the island of Ireland produced by Williamson et al. (2008).