Tree of Heaven identification

The Tree of Heaven Ailanthus altissima, native to northern and central China, was introduced to Britain in 1751. It was planted extensively in London Squares and elsewhere in parks, streets and gardens. It is now very common in urban areas and has spread naturally in the warmer parts of the USA by colonising waste ground. It is considered an invasive species in many countries and very difficult to eradicate because of its ability to re-sprout vigorously when cut.

Tree of Heaven identification – large Ash-like pinnate leaves with up to 21 leaflets, fruit ‘keys’ that turn orange in autumn, bark with vertical ‘snakes’. The leaves have a characteristic bad odour when crushed. At first sight the tree looks like an Ash but closer examination of the leaves shows the difference. Click on any photo to enlarge it.

 

Tree of Heaven

A Tree of Heaven in full leaf in August.

Tree of Heaven leaf
Each leaf has 11 to 25 leaflets. It is a pinnate leaf. At first sight the leaf looks like that of the Common Ash.
Tree of Heaven leaflet

Each leaflet is smooth-edged but has a single tooth at the base of the leaf.

Tree of Heaven leaves unfolding.

The leaves unfold red like this in May or June.

Tree of Heaven pinnate leaf

The leaflets are big, making the whole leaf very large. Photo taken in July.

Tree of Heaven male flowers
The male flowers come out in July. They emit a strong unpleasant odour to attract pollinators such as flies. The trees are dioecious with male and female flowers on different trees.
Tree of Heaven 'keys'
The fruit of female trees hangs, in the form of ‘keys’, like this in October. They look like Common Ash keys except for their colour. Most trees in urban areas are female.
Tree of Heaven bark

The bark has vertical ‘snakes’ like this.