The following is a very quick stab at the botany of Hackfall. More will follow shortly.
Hackfall could be described as a one sided gorge. It is North facing and very steep in places. The mosaic of plant communities is affected by the underlying geology and by very localised flushing from calcium rich water which arises from numerous springs. These springs, the river and the sheltered location produces a very humid microclimate at the bottom of the wood.
The steep upper slopes are more exposed, have underlying rock which typically gives rise to more acidic soil and the plants here are typical of acidic woodland. For example the area to the East of Mowbray Castle has extensive areas of bilberry (Vaccinium myrtillus), Great Wood Rush (Luzula sylvatica) and occasional patches of heather (Calluna vulgaris). The trees include the sessile oak (Quercus petraea) and Rowan (Sorbus aucuparia).
Much of the wood was clear felled in the 1930s and, it is said that very little replanting was completed. Some Scotts Pine (Pinus sylvestris) was planted and this has survived in small areas at the North end of the wood and near to Hackfall Farm. The owner at the time, a timer merchant, in effect asset stripped the property of its oaks and other valuable hard wood. Many of the trees that are present today have therefore regenerated naturally and in some areas the majority are less than 70 years old. This process of natural regeneration has allowed more agressive trees such as Sycamore (Acer pseudoplatanus) to dominate some areas. In general however there is a good mix of trees, including Ash (Fraxinus excelsior), Wych elm (Ulmus glabra) and in some areas Silver Birch (Betula pendula).
Under the trees in some areas is a shrub layer consisting mainly of Hazel (Corylus avellana) and holly (Ilex aquifolium).
Below this is a mosaic of plants typical of ancient woodland. The calcium rich springs flush some areas and allow plants that favour more alcali soils to compete.
Below are a series of photographs of plants found in Hackfall. All of these were taken in Hackfall mainly in June 2009.