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Flowering biology of Fraxinus excelsior L.
- the Common Ash, or European Ash

Fraxinus excelsior is an anemophilous (wind-pollinated) tree, distributed throughout Europe and Asia Minor, and it's the only species of ash in Sweden. It is deciduous and begins to flower before leafing, in Sweden around the end of April to beginning of May. The buds are black and the leaves emerge from the terminal buds after flowering around the end of May. Hermaphroditic flowers consist of one pistil and two purple stamens attached to the base of the ovary. There is no calyx or corolla. The flowers occur in many-flowered panicles (100-400 flowers) that emerge from lateral floral buds on shoots of previous year. The species is polygamous, which means that the sex expression of individual trees shows a continuum of gender, i.e. they have either staminate flowers, pistillate flowers, both unisexual flower types, only hermaphroditic flowers, or a combination of uni- and bisexual flowers on different branches (see photos below). There may even be different flower types within an inflorescence. Often the top flower in an otherwise male inflorescence is hermaphroditic. Staminate inflorescences contain more flowers than pistillate ones.

The trees seldom become older than 250 years. It starts flowering at an age of about 30 years and at around 100 years of age growth in height ceases. It can reach a height of up to 30 m and a girth of over 6 m. The tallest living ash tree in Sweden is 30 m (girth 4.72 m) and the biggest has a girth of 7.30 m (height 22 m).

The common ash has been studied as part of my PhD research and the results are included in my PhD thesis. Further studies have been conducted by the EU-funded research project FRAXIGEN.

An example of a closely related species is F. angustifolia, which is also wind-pollinated but has an andromonoecious breeding system.

For information on an entomophilous (insect pollinated) species, see the page of Fraxinus ornus.

Images of other Fraxinus species are here.

Fraxinus excelsior, April 29
April 29
Fraxinus excelsior, May 10
May 10
Fraxinus excelsior, May 25
May 25

Flowering sequence of a Fraxinus excelsior tree on the Swedish westcoast in 1995.


To see a larger picture, and explaining text, click on the thumbnails or choose from this list

All photos © by Eva Wallander

Overview [trees in spring | tree with view over Göteborg harbor | large solitary tree | tree on forest edge]
Hermaphrodite flowers [large inflorescences | smaller infl. | another branch | view of mast flowering | Four floral types]
Male flowers [branch with large inflorescences | another branch | close-up on male infl. | branch with pollen dispersing flowers | almost empty stamens]
Female flowers [branch with newly opened pistillate inflorescences | another branch | and another branch at a later stage | close-up]
Foliage and fruits [young fruits | fruits and leaves | mast fruiting]

Fraxinus excelsior habitat Fraxinus excelsior Fraxinus excelsior tree Fraxinus excelsior

Hemaphrodite flowers
Fraxinus excelsior Fraxinus excelsior Fraxinus excelsior Fraxinus excelsior flowering branches Fraxinus excelsior four floral types

Male flowers
Fraxinus excelsior male flowers Fraxinus excelsior male flowers Fraxinus excelsior male flowers close-up Fraxinus excelsior male flowers Fraxinus excelsior male flowers

Female flowers
Fraxinus excelsior Fraxinus excelsior Fraxinus excelsior Fraxinus excelsior

Foliage and fruits
Fraxinus excelsior young fruits Fraxinus excelsior fruits Fraxinus excelsior fruits

Maintained by Eva Wallander | Last updated: 2010-03-04