As the name suggests it is native to Italy - mainly the Southern parts. It is not as widely planted as the Common alder although it is happy with most soli types and locations. There are good sized Italian alders at the St Thomas pleasure grounds. Haven Banks and also Cowick Barton playing fields. Although it shares many charactertics of the Common alder it grows much taller and the catkins and cones are larger. The leaves are also cordate rather than raquet shaped. They will happily grow in wet areas such as along riverbanks but are perfectly well suited in green spaces and parks. They are also tolerant of poor air quality so can be used as street trees, altough I have not seen in Exeter as street trees.
Italian alder is fairly short lived which is a common trait of the Alder family. The average lifespan is 60 - 100 years. 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. They are massively overlooked by councils across the UK as they are one of the few tree species that can grow on extremely poor soils.
The leaves are heart-shaped, green and 5 - 12 cm in length. They are arranged alternately with serrated edges. The buds are purpleish red and a squat and egg shaped. They tend to be less sticky than the buds of Common alder. The bark is smooth, grey / green with lenticels.. The twigs have a light brown spotted stem which turns red towards the top. It is very late to shed it's leaves so even in December it may still have foilage.
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 February and April. Alder 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.
Another great thing about Italian 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 Common alder does not rot under water. 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.
OTHER USEFUL LINKS
- The mature female cones stay on the tree all year round
- Italian Alder is monoecious, which means that both male and female flowers are found on the same tree - but different parts
- Its natural habitat 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
PLEASE LEAF ME ANY FEEDBACK / COMMENTS
If there is anything out of place or wrong please contact me. Equally if there is anything you wish to add please let me know. The more information we have about Italian alder the better. Many thanks!