The hillside woodland of southern Limburg derive their special character from the transition from chalk-poor, gravelly soils on the upper reaches of the hills to chalk-rich soils lower down. On the higher parts are found the so-called Oak-Birch Woods associated with such shrubs as Mountain ash, Bramble and Alder buckthorn. Honeysuckle is the characteristic woody climber here. In places Bracken is predominant. Where the marly limestone (mergel) outcrops, a different type of woodland is found: the Oak-Hornbeam Woods, with Oak, Hornbeam, Ash and Spindle tree. Here, the characteristic climber is Traveller’s joy, often in copious displays.