[2] A more recent hypothesis, proposed by Proctor (1999), is that these forests are growing on soils which are highly acidic, such that hydrogen ion toxicity prevents the growth of non-adapted species.

The heath forests typically have a low, uniform canopy approximately 20 metres high, with thick underbrush and rich growth of moss and epiphytes.

[2] In contrast, padang woodland is relatively open, with shrubs and trees up 5 metres tall, and a ground layer of sparse grasses and sedges.

As an adaptation to the nutrient-poor conditions, some heath forest species have small, hard, thick sclerophyll leaves which are low in nitrogen.

Heath forests are also characterized by many plants of Australasian origin, including trees of families Myrtaceae and Casuarinaceae and the southern hemisphere conifers Agathis, Podocarpus, and Dacrydium.