Jas - incorrect. The earliest plantings occurred under Edward I, in SW Pembrokeshire, the Gower, and the towns of Conway, Carnarvon, and Beaumaris.
I meant within Ireland, but your point is taken.
I've checked back though, and it's not quite correct. The planting of Flemish settlers in two
cantrefi (a Welsh word borrowed into English as "hundreds", btw) of Southern Pembrokeshire occurred much earlier than that, under Henry I. Dutch appears in fact to have been spoken in that area until around 1350.
And I know you meant within Ireland.
Well they were not plantings per se, but Anglo-Norman interference; on invitation from squabbling Gaelic Chieftains, begin around 1170 with Strongbow and Henry II. The power of the Anglo-Hiberno-Norman lords ebbed and flowed for centuries thereafter but they always had a strong foothold in Leinster or specifically "the pale" The Scots and Welsh should have known by then not to invite an English king to broker a dispute.
The things I pointed out were actual plantings of settlers, by royal authority, granting them special rights to differentiate them from the natives, much as later in Ireland.
Anything in your post from "but" onwards is of course correct.
(Strongbow was a Welshman on his mother's side by the way, and the bulk of his original invading army was probably monoglot Welsh.)