Melia azedarachBead tree

The bead tree forms a rounded to open crown, typically between 7 and 12 m in height and 6 to 10 m in spread, with bipinnate foliage that gives a light texture and filtered shade during the growing season. The stem develops dark brown bark with narrow longitudinal furrows and pale patches at maturity. Growth is fast: in favourable conditions of full exposure and well-drained soil, it reaches a functional size for avenue planting three to five years after transplanting.

Flowering takes place between April and June, in axillary panicles of 20 to 40 cm with lilac flowers of intense scent, often described as chocolate-like. The fruits are yellow drupes of about 1 cm, which persist on the tree after leaf fall and extend the visual interest through the winter. The foliage turns golden yellow in autumn, giving a stable phase of colour before leaf fall.

Tolerance of heat and water stress is high: the species performs well in sandy, loamy and well-drained chalky soils, and withstands prolonged periods of summer drought once established. It withstands minimum temperatures of about -15 °C, which makes it viable throughout mainland Portugal, including situations of moderate frost in the northern interior. It is practically immune to pests and diseases in Portuguese conditions, which positions it as a functional alternative to genera under plant-health pressure. It requires full exposure; it tolerates moderate salinity.

There are, however, design constraints that must be weighed. Average longevity is around twenty years, significantly below species such as plane, lime or cork oak, which implies predictable replacement costs in the medium term. The wood is relatively brittle, with susceptibility to branch breakage in episodes of strong wind; early formative pruning to reduce heavy lateral branching is advisable in exposed avenue plantings. The fruits are toxic to mammals when eaten in quantity, a relevant fact for spaces in public use with children or pets. In addition, the species is flagged as invasive in several international contexts and naturalises readily through dispersal by birds; in a municipal project, it is important to check the local regulatory framework and to plan for the management of self-sown specimens.