The Plantation of Munster & Plantation of Ulster were established by the crown under Queen Elizabeth I for 'planting' protestant farmers onto forfeited estates of rebel Irish noblemen. In Munster such 'planters' or 'undertakers' were mostly English but in Ulster they were frequently Scottish.

Following the defeat of Gerald FitzGerald, 15th Earl of Desmond ("The Rebel Earl") in the Geraldine Wars and his murder in 1583 at Glenageenty, Ballymacelligott, his vast estates in Munster, some 500,000 acres, were declared forfeit to the crown and plans were laid for the Plantation of Munster. The confiscated lands were surveyed, 210,000 acres being granted to new settlers. Good land was divided into thirty-six estates varying in size from 4,000 to 12,000 acres, any remaining poor land being additional to this. The land was granted to English protestants who had performed some service and who undertook to plant their new lands with a number of protestant tenants.

Sir Edward Denny, Knt (1547-1599) of Bishops Stortford, Hertfordshire, was a godson to King Edward VI; a Gentleman of the Privy Chamber to Queen Elizabeth I; Commander under Admiral Lord Thomas Howard. He served against the rebel Earl of Desmond and also against the Spanish in Ireland, playing a prominent role in the Battle of “Dun An Oir” on the Dingle peninsula, where approximately 600 Spanish soldiers who had come to assist the Geraldines were killed by English forces commanded by his cousin Sir Walter Raleigh.

For his services he was granted in 1587 a reward of 6,000 acres of Desmond's forfeited estates, including the town and the Earl's chief castle of Tralee.  He became Governor of Kerry & Desmond and one of the Council of Munster but did not himself settle there, although he made many grants of land to others, who themselves or their sons settled as “Undertakers in the Plantation of the Province of Munster”. Edward Denny was knighted, "Knight Banneret", in Ireland on 26-October-1588.

The three principal undertaker families brought into Tralee by Sir Edward Denny, Knt to settle on portions of his own grant of lands were Blennerhassett, Chute & Morris. Sir Edward in 1590 (32 Elizabeth I) granted Ballycarty and other lands near Tralee to Thomas Blennerhassett of Flimby Hall, Cumberland. Thomas is said to have visited Kerry but it was his son Robert Blennerhassett who settled, becoming ancestor of the Kerry & Limerick Blennerhassett families.

Sir Edward Denny's son Sir Arthur (1584-1619, also sometimes called Sir Edward) did settle in Ireland, at Tralee Castle in Co.Kerry; he commenced rebuilding of the town of Tralee and from him descended the Denny family of Tralee. He also held Carrigafoyle Castle on the River Shannon in North Kerry, in earlier times the principal seat of the ancient family “O'Connor Kerry”. Substantial ruins of Carrigafoyle Castle remain.

The old Tralee Castle of the Geraldines was rebuilt by the Denny family as their seat and fortress in Desmond, rebuilding being completed in 1627 by Sir Edward Denny, Knt (1605-1646), father-in-law of John Blennerhassett of Ballycarty. Tralee Castle stood close to the present-day junction of Lower Castle Street and Denny Street. In the rebellion of 1641 it was ruined, then in 1691 both Castle and town were destroyed by fire, set by Jacobite forces anticipating the arrival of Williamite forces from Limerick. Charles Smith's 1756 work “The Ancient and Present State of the County of Kerry” contains a “Plan of Traly” showing the location & extent of the Castle at that time.

Rebuilt again in 1802 but finally demolished in 1825, stones from Tralee Castle were used in the construction of present-day Denny Street. Only a few traces of the castle remain, although some foundation walls were uncovered in the 1990s. A unique watercolour of Tralee Castle, owned by the present head of the family Sir Anthony Denny, is illustrated in "The History of Tralee", by Kerry historian Gerald O'Carroll (published 2009).

The Church of St.John the Evangelist, Ashe Street, Tralee (C.of I.) was closely associated with the Denny family of Tralee Castle and the Denny Family Bible (a 1639 King James Bible) is kept at the church in an ancient wooden box. A notable volume in itself, the bible also contains a history of the Denny family at Tralee over a period of 300 years and has many Blennerhassett references. When no service is taking place the Church is usually locked, but arrangements can be made for visitors to view the church interior.