In this paper we discuss three approaches to the modelling of tree cro
wn development. These approaches are experimental (i.e. regressive), t
heoretical (i.e. analytical) and computer-simulational [by L(indenmaye
r)-system] modelling. The common assumption of these approaches is tha
t a tree may be regarded as a fractal object, being a collection of se
lf-similar objects that combines properties of two- and three-dimensio
nal bodies. We show that a fractal measure of crown can be used as the
link between the mathematical models of crown growth and light propag
ation through the canopy. The approach using the Lindenmayer computer
system allows crown development to be visualized and the model to be c
alibrated according to experimental data. Different stages of the abov
e-mentioned approaches are described. The experimental data for spruce
, the description of the computer system for modelling and a variant c
omputer model are presented.