2018:034 - Hillsborough Castle Gardens redevlopment 2017, Down

The regeneration of the walled gardens and demesne was divided into 11 separate, but related, projects. Of these 11 projects only three required any archaeological mitigation:

• Project 1 (Figure 1): Upper Stableyard Visitor Facilities and associated Forecourt. Specifically, groundworks relating to the construction of the extension to the stables.

• Project 2 (Figure 2): Lower Visitor Facilities. Specifically, groundworks in the vicinity of the surviving hothouse wall.

• Project 10 (Figure 3): Moss Walk.

Of the three areas within the development which required monitoring, only Project 2 (Hothouse) contained archaeological material, Projects 1 and 10 were devoid of archaeological remains.

The hothouse is a historically significant garden feature and its surviving upstanding wall has been stabilised and will be preserved within the new visitors' centre. The sub-floor elements of the hothouse which were exposed during the excavation have been preserved under a layer of stones, and a rafted concrete floor.

The structure excavated within Project 2 was clearly a hothouse. It is recorded as such from a plan of the gardens from the 1770s, and there can be no doubt as to its general function. There is some uncertainty as to the more specific function of the building, i.e. was it a pinery (pineapples), vinery (grapes) or just a more general, non-specific variety hothouse. Although there was a fad for the growing of pineapples within the hothouses of the stately homes of the 18th century there is no evidence to definitively state that this was the case. The alterations carried out during Phase 2 may indicate a change of function from a general hothouse to a vinery. Vines grow best if the roots are planted outdoors and the vines are trained into the hothouse. By breaking through the south-west foundations (S4 and S8) and inserting the brick arches the vines could easily be planted outside and trained inside without the hothouse losing much heat. Regardless of the plants being cultivated within the hothouse they all operated in a similar fashion (see Figure 5, elevation of pinery/vinery from Kensington).

The hot house comprised two rooms or buildings. The larger hothouse, where the plants were cultivated, and the smaller furnace or stove room. The two rooms were separated by a large cavity ‘fire wall’. The main body of the hothouse would have been constructed against the ‘fire wall’ and brick-built at either gable end, the north-west and north-east ends of the building in this case. The remainder of this part of the structure would have been constructed using panes of glass held within a frame.

On the opposite side of the ‘fire wall’ the stove or furnace room would have simply held the stove or furnace that would have been fired up and used to heat the hothouse. The ‘fire wall’ consisted of two parallel brick walls with the gap between the two being used as a flue. The furnace or stove was constructed into this wall and, when lit, the heat would be carried up through the ‘fire wall’ heating the adjacent hot house. Originally a chimney would have been present along the ‘fire wall’ to both draw the heat up and to vent the smoke.

Historic Royal Palaces had also requested that the area of the walled garden be subject to a metal detector survey, this was not a requirement of the planning condition, but a voluntary survey. The metal detector survey did not uncover any significant archaeological material.

Northern Archaeological Consultancy, 638 Springfield Road, Belfast