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ALDER

COMMON ALDER

Alnus glutinosa

Birch Family [Betulaceae]

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category
category8Trees
category
category8Broadleaf
category
category8Deciduous
status
statusZnative
flower
flower8red
flower
flower8green
flower
flower8cream
petals
petalsZ0
type
typeZcatkins
sex
sexZmonoecious

25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
  Early in the year the male and female catkins appear whilst the tree is still leafless after Winter. These Alder trees are all growing alongside a ditch with the sea in the distance beyond. The dark-green leaves under the eaves are those of the deadly-poisonous Hemlock Water-Dropwort common around these parts.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
 The male catkins are a lot longer than the short female ones.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
   The longish male catkins with last-years mature female 'cones' (black).


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
   The longish male catkins are pale-green at first going through cream and yellowish-green to orange. Last years mature female 'cones' (black).


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
  Last years mature Female 'cones' are hard and woody and come in groups of 3 to 6 which hang from a common stalk. They are between 8 - 28mm long.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
  Last years mature female 'cones' later open up to release the numerous seeds which are narrowly winged.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
  This years fresh crop of female catkins and at 1.5cm far shorter than the male catkins. Red at first they turn green before going woody and cone-like over winter and finally turning black when ripened with seeds.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
  This years fresh female catkins, which consist almost entirely of short red styles tipped with clear stigmas. Interspersing the female flowers are many pale-green rounded 'bracts' which might (?) become the scales in the 'cones'.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
  This years long male catkins and this years short red female catkins just above them showing size difference between male and female. Male catkins are up to 10cm long. The male catkins appear over winter and at first are a striking wine-red colour, but later turn yellowish-green in spring when they open up displaying their anthers.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
  Male catkins showing their many tiny cream-coloured anthers. They are in bunches of 2-3.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
 Many stamens per flower.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
 Your Author is not quite sure what all the structures are in the male catkin. The anthers are plain to see, but are those compacted bunches also fresh anthers?


LATER IN THE YEAR

5th July 2014, Leeds & L/pool Canal, Rimrose Country Pk, Sefton Coast. Photo: © RWD
Later in the year the catkins have dropped off and the leaves grown afresh.


5th July 2014, Leeds & L/pool Canal, Rimrose Country Pk, Sefton Coast. Photo: © RWD
Leaves up to 10cm long are shiny green and mostly hairless both sides except for some long hairs in the axils on the underside. They are more round with a much less pronounced point at the end than other Alder species (of which there are over 4, some not native such as Italian Alder).


5th July 2014, Leeds & L/pool Canal, Rimrose Country Pk, Sefton Coast. Photo: © RWD
Main veins parallel at an angle of about 70° from each other. Teeth not deep but irregular, sometimes rounded.


5th July 2014, Leeds & L/pool Canal, Rimrose Country Pk, Sefton Coast. Photo: © RWD
Underside of leaf shows the cross-veins communicating between the main veins. Stems green and with tiny pimples (lenticles - which are orange) and which exude a sticky sap which is why young twigs feel sticky (also hence the glutinosa in the Scientific name). Fringed Water-Lily floats atop the far side of the canal.


5th July 2014, Leeds & L/pool Canal, Rimrose Country Pk, Sefton Coast. Photo: © RWD
Typical reddish appearance of upper surface of some leaves.


25th March 2016, Velvet Way, Southport, Sefton Coast. Photo: © RWD
Young bark shows horizontal features.


1st Nov 2009, Middlewood Way, Marple, Gtr N/cr. Photo: © RWD
Newly-sawn wood shows a striking bright orange-red coloration. Only sometimes are Alder trees multi-trunked, as was once the case here before it was felled.


17, March 2010, Tame Valley Way, Gtr M/cr. Photo: © RWD
Older bark shows wavy vertical features.


Hybridizes with : Grey Alder (Alnus incana) to produce Alnus × hybrida which occurs frequently wherever both parents meet. The leaves and fruit are intermediate in character between the two in various combinations. It occurs in Cardiganshire and County Roscommon.

Can be confused with : Hazel (Corylus avellana) which has similarly rounded leaves but they are softly hairy in comparison to the shiny green of Alder.

No relation to : Alder Buckthorn (Frangula alnus) [a tree with similar name but belonging to Buckthorn Family (Rhamnaceae) which includes the poisonous Buckthorn (Rhamnus cathartica) itself].

Common Alder is native to the UK and commonly grows in alder carr woods where there is standing water. It also grows in bogs and swamps or alongside streams and ditches and can be found as high up as 700m above sea-level. It is often used for flood mitigation. Left to fend for itself it grows into an elegant domed tree (or a conical tree if younger) up to 25m high, but it is often coppiced to produce long straight poles. Growing near watercourses it helps to stabilise the banks of rivers and streams preventing erosion by means of their tough roots. It can live for up to 60 years. The timber it produces is useful for use in wet conditions such as piers and lock gates. Clogs are made from it, and in times past it was said to produce the best charcoal for use in gunpowder.

The roots develop nodules which contain the nitrogen-fixing bacterium called Frankia alni which engages in a symbiotic relationship with the tree, exchanging nutrients, the bacterium fixing nitrogen gass from the air to produce water-soluble nitrogenous compounds for the tree, whilst the bacterium obtains its supplies of sugar from the tree. Because it can grow in soils lacking nitrogen, it can also grow where other trees cannot grow for lack of nitrogen. The now soluble nitrogen compoiunds enhance the fertility of the soil. In 2002 a water-borne root-pathogen called phytophthora started affecting Alder which is killing many trees off by causing root-rot and lesions on stems which bleed a rusty brown fluid.

A green dye obtained from the catkins was once used as a camouflage dye for clothes worn by outlaws such as Robin Hood.


  Alnus glutinosa  ⇐ Global Aspect ⇒ Betulaceae  

Distribution
 family8Birch family8Betulaceae

 BSBI maps
genus8Alnus
Alnus
(Alders)

ALDER

COMMON ALDER

Alnus glutinosa

Birch Family [Betulaceae]