Ailanthus altissima

Ailanthus altissima (tree of heaven) has spread over a large part of Europe, and it mostly invades forests via roads or trails. As a fast growing tree it tends to create dense pure stands that may have a strong impact on natural biodiversity. It can also be found in agricultural (including horticultural) and domestic habitats. This tree can also invade urban areas, where it can cause damage to buildings and other structures as well as transport networks, including roads, railways, and other constructed hard-surfaced areas. Control of this invasive species is particularly difficult as any disturbance to above ground structures, including cutting, chopping or girdling, promotes production of sprouts that may emerge from the root, the root crown and the stem. Moreover, shoot fragments may produce adventitious shoots and roots. Practical solutions for containment and local eradication will be developed within WP3, including mechanical control (cutting of mature female trees to avoid seed dispersal, manual uprooting of young individuals, repeated cuttings with brush cutters of young individuals, girdling) and optimized use of chemical (spraying of herbicides on cut stumps and basal bark, stem injection of herbicides, foliar spraying of herbicides on plants shorter than 150 cm).

Species Description

Habitus: A. altissima is a deciduous tree, 5-30 m tall. Stem: erect, with smooth and light brown/gray bark in the young plants that becomes slightly darker, rough and fissured when adult.
Roots: superficial roots with rhizomes able to produce numerous sprouts.
Leaves: dark green, alternate, compound with a single leaflet at the tip and with entire margin, with 1-4 teeth at the base and with a strong smell. Leaves of young seedlings are reddish-brown in color.
Flowers: panicle inflorescence at the tip of the branches, 10-20 cm long. Separate male and female flowers are produced on different plants. Flowers are numerous, small, white or yellow greenish in color with reddish shades. Male flowers have strong smell, while female flowers are odorless.
Fruits: winged fruits grouped in clusters with one seed centered in the middle of the fruit. Fruits are persistent on the tree during winter. Fruit clusters are reddish in color when newly formed and become brownish/reddish yellow at maturity.

Biology and Ecology

Ecological requirements: A. altissima is a pioneer species, highly adaptable to different soil types. It can survive in different environmental conditions, such as: saline, poor and compacted soils and in dry, heat and polluted environments. As it grows fast it can rapidly colonize disturbed and unmanaged areas.
Pollination: small flies, beetles and honeybees have been recorded as pollinator of A. altissima. Seed production and dispersal: the species produces up to 325,000 seeds grouped in several hundred clusters per plant. Seeds are dispersed by wind; however, they can also be dispersed by water, birds and machinery.
Plant propagation: A. altissima can sprout from roots and from the stump. Sprouts are produced up to 15 m from mother plant and have a rapid growth, till 3-4 m in a single season; seedlings have slower growth, about 1-2 m per year. Root sprouting is stimulated by plant cutting and root damages.
Flowering period: occurs from May to July (Northern Italy).
Environment: A. altissima can grow in different environments: natural, urban, and industrial areas including roadside and railways. It infests forests, meadows, riparian zones, uncultivated or abandoned areas. The species has been reported to infest mainly plain areas but it can grow up to about 1000 m a.s.l.

Impacts

Ecosystems: A. altissima is a short-lived species (30-50 years) but its ability to sprout constituting pure areas of infestation, that hampers the growth of other species, permits to dominate the infested sites indefinitely. The reduction of biodiversity caused by this species is also due to its allelopathic potential: bark and leaves can release allelopathic compounds that inhibit or affect the germination and the growth of other plants.
Agriculture: leaves are toxic for animals, but because of the bitter taste are relatively unpalatable compared to other species.
Human health: bark, leaf and root saps can cause skin irritation to some people due to the alkaloid ailanthin. Pollen may cause allergy reactions.
Buildings: the fast-growing root system can damage buildings, foundations, sidewalk, roads, archaeological sites and also roofs and cracked walls of unmanaged buildings.

Management approach

For Optimized chemical control: Chemical control in amenity and non-agricultural area
For Cultural control: Mechanical interventions (cutting, girdling)/ reduction of seed production

Solution proposed by EMPHASIS

For Optimized chemical control: Guidelines for sustainable IPM control of weeds in agricultural and non-agricultural areas (PU)
For Cultural control: IPM protocol

Contact person/organisation

Aldo Ferrero (UNITO)