Alnus glutinosa
Contents
Common Names
Common Alder, European Alder
Family
Description
A deciduous tree which thrives in damp conditions; small glossy, dark-green rounded leaves, green foliage last long into autumn. Buds and young leaves are slightly sticky with a resinous gum, hence its name 'glutinosa'.
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File:3 E.jpg fruit |
File:3 F.jpg nut |
| Foliage | deciduous |
| Group | broadleaf |
| Toxic Parts? | no |
| Height | 18 - 25m |
| Crown Diameter | m |
| Crown Shape | pyramidal |
| Shade Tree? | yes |
| Autumn Colour? | yes |
| Age | 80-150 years |
| Time to Maturity | - years |
| Flower Colour | greenish yellow (male), red (female) |
| Fruit Colour | |
| Bee Friendly? | - |
Native Areas
All of Europe, extending into western Asia and south to North Africa [1].
Preferred growing conditions
Alder thrives in damp, waterlogged conditions, growing close to rivers and marshy ground [1].
| Soil pH Range | 4.5 - 8 (acidic - slightly acidic - neutral - slightly alkaline ) |
| Soil Types | sand, silt, clay, loam, chalk |
| Drainage | poorly drained |
| Soil Fertility | low |
| Sunshine | part sun and full sun |
| Soil Moisture | moist |
| Tolerates Exposure | yes |
| Growth Rate | - 0.5 fast |
Hardiness
| RHS | USDA | EGF |
| H | 5A | H1 |
How to plant
Water container-grown and rootballed trees well and allow to drain an hour before planting. While it drains dig out an area for the tree that is about 2 to 3 times the diameter of the container or rootball and the same depth as the container or rootball. If the soil is compacted loosen with a fork (this includes the sides of the hole). But beware of having soil that is too loose on the bottom as this will cause the tree to be lower than desired upon watering.
- If container-grown, put the tree on its side and remove the container. Place in the hole and loosen the roots around the edges without breaking up the root ball too much. Check the depth by place a cane or stick across the diameter - only the root collar should be below and not the main stem.
- If planting a balled and burlapped tree, remove ties or nails from the burlap at the top of the ball and using a knife if necessary, pull the top of the burlap back, so it does not stick out of the hole when the soil is replaced. Synthetic burlap should be completely removed as it will not decompose. Note burlap sticking out of the hole can wick water away from the tree.
- For bareroot trees, feel the moisture of the roots by hand - if dry, dunk them in an bucket of water for 10-15 seconds and replace the packaging (if you are not going to plant at that time). Do not plant too deeply - only plant up to the root collar. i.e. the stem should not be covered in soil. Ensure roots are planted firmly and have good contact with the soil.
Fill in the hole with soil and compost, but do not add less than half of the original soil.
Using the soil, create a water ring around the outer edge of the hole. Not only does this conserve water, but it will also direct moisture to the perimeter roots, encouraging outer growth. Once the tree is established, the water ring may be levelled. Studies show that mulched trees grow faster than those unmulched, so add a 3 inch layer of pinestraw, compost, or pulverized bark over backfilled area.
Only prune lower damaged branches if necessary. Water newly planted trees regularly in their first year. Staking is also important in new trees and in exposed areas - a 1 m stake at 45 degrees crossing the stem at a height of 15 cm can provide good support. Be careful of the binding of the stake to ensure the tree is not strangled. Binding should be checked in the second year, as the stem will thicken.
When to plant
Early to mid-Autumn, for cold, wet sites wait until early to mid-Spring. Container-grown trees can generally be planted all year round except when it is very hot and dry or the ground is frozen.
Tree care
| Hedging Potential | no |
| Balcony/Roof Terrace | no |
| Indoors | no |
Potential Pests and Diseases
| Pests | |
| Diseases | phytophthora |
Ecology
Alnus glutinosa is most noted for the symbiotic relationship with the bacterium Frankia alni, which forms nodules on the tree's roots. This nitrogen-fixing bacterium absorbs nitrogen from the environment and fixes it into a form available to the tree. In return, the bacterium receives carbon which is produced by the tree through photosynthesis. This relationship, which improves the fertility of the soil environment, has established A. glutinosa as an important pioneer species in ecological succession. A. glutinosa is also a host to a wide variety of moss and lichen. Some common species found on A. glutinosa include: Tree Lungwort (Lobaria pulmonaria), Stenocybe pullatula, and Menneguzzia terebrata [2].
History and Human Connection
The common alder is especially associated with the Celts, where the tree was significant in their daily life and spirituality.
Uses
- As a timber, A. glutinosa is very durable underwater and is thus used in building foundations in Venice and Amsterdam
- As the wood is soft, flexible, somewhat light, it can be easily worked on as well as split. It is also valued furniture making, wood cuttings, clogs, pencils and bowls. In fact, cabinet makers value this wood very much [2].
- The bark is used in tanning and dyeing
- It is a traditional wood burnt during the smoking of foods
- The bark possesses a wide range of medicinal properties
- Cultivated as a bonsai
- As a pioneer species in new landscapes
References