Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Rosales
Family: Rosaceae
Genus: Prunus
Subgenus: Cerasus
Species: P. avium
Binomial name: Prunus avium
Common name: Sweet cherry, Wild cherry, Bird cherry, Wilding cherry, Mazzard, Gean.

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Toxicity: All parts of the plant except for the ripe fruit are toxic, containing cyanogenic glycosides. Symptoms of gasping, weakness, excitement, pupil dilation, spasms, convulsions, coma, and respiratory failure can occur if ingested. 

Prunus avium is fast-growing a winter-deciduous tree in the rose family, originating from Europe and Asia. It is a small to medium-sized tree, up to 12 m high, with erect or spreading branches. In New Zealand, it flowers during late winter, early spring (August/September/November). Fruiting occurs early/mid summer.
The non-fragrant, five-petalled, flowers are white (about 3-4 cm across) and are pendant or spreading and are borne on single or in small clusters. They have yellowish stamens, a superior ovary and are hermaphroditic. They are pollinated by bees and insects.
The fleshy dark red to black fruit (1-2cm) are drupes, each with a single seed enclosed by a hard endocarp (stone) that is 6–8 mm long. The endocarp is surrounded by a juicy, fleshy pericarp (fruit wall) which is very attractive to frugivorous birds. Kereru, blackbirds, thrushes and starlings are the most important frugivore and seed disperser.
New foliage appears at the same time, or immediately after flowering. The thin green oval leaves are alternate (30-150 x 25-70 mm) and they have toothed margins that point towards the apex of the leaf. There are two to five small red glands on the leaf petiole. In autumn the foliage turns red, orange or yellow and is shed.
The trunk has smooth, grey-brown bark with prominent horizontal grey-brown lenticels on young trees. Lenticels are raised areas of loosely packed cells which are formed by the phellogen. n. They allow gases to pass into and out of the trunk or branch. On old trees, the bark becomes a dark blackish-brown and is thick and fissured.

In New Zealand, it is classed as a wilding Prunus species. It is invasive because trees have escaped intentional plantings because birds which digest the drupes and disperse the seeds in their droppings. Trees will also spread by suckers (locally). They are found on roadsides, open and disturbed habitats and forest edges. They are hardy shrubs and tolerate cold and dry conditions. They shade out forest under-stories and displace native vegetation. The seeds are long-lived.

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Just starting to flower. Photographed late August
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The new leaves late August.
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The fruit.
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Thanks to Wikipedia for text and information:

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