Epipactis helleborine
The woodland policies at Monkcastle are classified as one of the relatively few North Ayrshire 'Ancient Woodland' sites. Aspen (Populus tremulans) has been recorded here; liverworts, ferns, and mosses are common due to the conditions of continuous high humidity. The Scottish Wildlife Trust (SWT) have designated Monkcastle as part of Listed Wildlife or Local Site for Nature Conservation (LSNC) number 27, together with Monkcastle House, Dalgarven and Smithstone. Aspen (Populus tremula) is the most notable species present, however the presence of Broad-leafed Helleborine (Epipactis helleborine) indicates a woodland containing many mature deciduous trees of some habitat value, together with wet flushes containing yellow flag iris, soft rush, lesser spearwort and golden saxifrage.