Wales has always been known as a pastoral society, in that farming was a less common occupation than herding. Crops were grown, however, and new archaeological studies are shedding light on the nature of that form of agriculture. ”In about 4,000 BC farming was introduced into Wales, although the people still used stone tools.” http://www.localhistories.org/wales.html
“The discovery of corn-dryers with early medieval radiocarbon dates has contributed to the growing number of early medieval examples excavated in Wales which can throw valuable light on the crops grown, their ratio to each other and how they were processed. South Hook (Herbranston) is a particularly important site since several corn-dryers were excavated together with rotary quern-stones and a significant assemblage of charred grain samples.
Two types of oats (bristle oats and common oats) as well as hulled six-row barley grains were the main crops grown. These would have been well-suited to the poor acidic soils of the region. It was also argued that bristle oats and barley were grown together in order to provide a failsafe crop on marginal land and that some of the barley was malted for beer. Wheat grains, which would have required better soils, were present but rare. Flax seeds and hazel-nut shells were also recovered (Carruthers forthcoming). In contrast at the slightly later site of Maenclochog the sample from a hearth produced mainly oats and rye (Carruthers forthcoming), but a very similar picture is presented by the evidence from Newton (Llanstadwell), where two corn-dryers were excavated together with the upper stone of a rotary quern.
Carbonised grain from the base of one dryer provided a radiocarbon date of cal AD 720–960 (2 sigma). Analysis of the charred grain has indicated that barley (six-row and two-row) was being grown probably alongside oats (bristle oat?) and in all likelihood wheat was also being cultivated. The weeds discovered were also consistent with those found in corn fields and charcoal samples suggest that oak, hazel and cherry/blackthorn were growing in the vicinity (Crane 2004, 11–18). http://www.archaeoleg.org.uk/pdf/reviewdocs/earlymedreview.pdf
Note that a ‘corn-dryer’ does not mean that the Welsh were growing ‘corn’, a new world crop. All grains in the UK are often called ‘corn’. A corn dryer, then is a ‘grain dryer’ in American parlance: ”Corn-drying kilns were used in the medieval and post-medieval periods. They were built either to dry corn before threshing in areas where it was not able to ripen before harvesting. It was also used to dry damp corn before it was ground into flour. They are usually either simple stone-lined bowl-shaped ovens built into a bank side or larger, freestanding buildings. Hot air, usually from a peat fire, would rise through a wooden grill covered with mats or straw with the grain laid on top.” http://www.keystothepast.info/durhamcc/K2P.nsf/K2PGlossary?readform&GLOSSARY=corn-drying+kiln
This is not to imply that Wales wasn’t predominantly pastoral, but that there is evidence of farming among the native Welsh.