This alder is one of the more unusual types of alder and really stands out in February when the male catkins are present. Unlike the Common alder which is a native species of tree to the UK, the Cut leaved alder 'Laciniata' was Introduced from France in the 1820’s. Historical records advise that Trochereau De la Berliere found this tree growing in the wild, which he took and planted in his garden near Saint Germain. It is thought that all the trees of this form are descended from one grown in a garden near St Germain in France in the early 19th century. In Exeter this tree is quite rare - I have only come across a handful of these trees during my study. They make excellent street trees as they can tolerate pollution and typically grow up to 20m in height - making them easier to manage.
Like most members of the Alder family it is fast growing and fairly short lived. The average lifespan is likely to be no more than 80 years old. Like all members of the Alder family it has a very special ability - to fix Nitrogen in the soil. It has a symbiotic relationship with a friendly bacterium called Frankia alni. This friendly partnership allows the airborne Nitrogen that is trapped underground to be converted into soil based nitrates. Similar to Silver Birch - it is a pioneer species so will be the first to colonise open / barren land. Due to the huge benefits that alder provide to the ground - they should be planted more widely in industrial estates and other areas with general pollution. This tree is tolerant of urban pollution and is suitable as a street tree but should not be planted close to houses due to the shallow spreading roots.
The leaves are deeply lobed and slightly toothed
The leaves are shed from November onwards
The leaves are deeply lobed, slightly toothed and the lobes are lanceolate. Like other alder species the leaf arrangment is alternate. The bark is smooth, grey / green with lenticels. It is very late to shed it's leaves so even in late November it may still have foilage. On a windy summers day the leaves are almost feathery and easily flutter on the gentlest of breezes. The canopy is quite open and the form of the tree is typically conical - but quite widely spread. It is not fussy of soil conditions but will not tolerate chalk. It will quite happily grow in damp conditions and can also tolerate salt spray so can be planted in coastal areas.
During pollen release the male flowers are lovely shades of yellow, red and brown
The fruit is a woody cone like structure and the seeds are dispersed by wind and water
The flowers are on catkins which appear between December and March which is earlier than most other types of Alder. It is monoecious, which means that both male and female flowers are found on the same tree but different parts. The male catkins are yellow and pendulous, measuring 4–10cm. The female catkins are red / green and oval-shaped and are grouped in numbers of three to eight on each stalk. Once pollinated by the wind, the female catkins gradually become woody and appear as tiny, cone-like fruits in winter. They open up to release seeds, which are dispersed by wind and water. A key feature of this tree is the winter interest of the pretty male catkins as well as the woody / mature female cones.
The tree is typically conical in nature but widely spread
The bark is smooth, grey / green with lenticels
Another great thing about alder is the roots can help against flooding as they can soak up a lot of water as well as helping to stabilise the structure of riverbeds and other bodies of water. Interestingly the wood of alder does not rot under water. In the wild this allows all sorts of creatures to make homes within the roots such as otters and other water dwelling mammals. As it is often by water it also provides shelter for smaller fish. Aquatic insects such as water beetles, caddis flies and stoneflies feed off the leaves that fall into the water. Small birds such as Goldfinch eat the seeds and many insects and spider species are associated with this type of alder.
Cut leaved alder 'Laciniata' was Introduced from France in the 1820’s
Historical records advise that Trochereau De la Berliere found this tree growing in the wild, which he took and planted in his garden near Saint Germain
It is a deciduous tree which means it sheds it leaves annually
It is a fast growing tree - sometimes multi-stemmed
It is tolerant of pollution and is suitable as a street tree
The mature female cones stay on the tree all year round
Alder is monoecious, which means that both male and female flowers are found on the same tree - but different parts
The natural habitat of most Alder species is moist ground near rivers, ponds and lakes and it thrives in damp, cool areas such as marshes, wet woodland and streams where its roots help to prevent soil erosion
It grows well from seed and will quickly colonise bare ground
Because of its association with the nitrogen-fixing bacterium Frankia alni, it can grow in nutrient-poor soils where few other trees thrive
Catkins provide an early source of nectar and pollen for bees, and the seeds are eaten by the siskin, redpoll and goldfinch
The wet conditions found in alder woodland are ideal for a number of mosses, lichens and fungi
Alder roots make good nest sites for otters
The wood has been used in the construction of boats, sluice gates and water pipes, and much of Venice is built on Alder piles
Currently Alder wood is used to make timber veneers, pulp and plywood
The roots have nitrogen-fixing nodules which make it an excellent soil conditioner
They are also used in flood mitigation
The trees are very quick to establish and will grow at a rate of 1 metre or more per year when young
In the past the powdered bark has been used as an ingredient of toothpastes
The bark and the fruits contain up to 20% tannin
The wood also makes a good charcoal
Venice is built on foundations of alder trunks
Alder wood is still used today to make the bodies of top end Fender electric guitars such as the Stratocaster
Alder cones have been used for many years by European breeders of soft water fish as a natural way to protect eggs from fungus and bacteria. See a YouTube video for more details
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