Alder Alnus glutinosa
ABOUT
Alnus glutinosa, widely known as the common alder, is a deciduous tree characterized by its rounded shape and sticky young twigs. The leaves of the common alder are simple and alternate, with a distinguishing feature of being glutinous when young, which is referenced by its species name. The leaf shape is somewhat rounded with a subtly wedge-shaped base and a serrated edge, and they are glossy and dark green on the top with a paler underside. The common alder is known for its catkins which are present during the winter and early spring. The male catkins are long, slender, and pendulous, yellowish in color, and they release pollen early in the season. The female catkins, in contrast, are much shorter and after pollination, they become woody, resembling small cones. These cones mature in the autumn to release seeds, but they often stay on the tree throughout the winter. The bark of the common alder is smooth and grayish when the tree is young but develops shallow fissures as it ages. Another distinctive feature of the common alder is its ability to form a symbiotic relationship with nitrogen-fixing bacteria found in nodules on its roots. This feature allows it to thrive in wet, marshy places, often stabilizing the soil with its root system. Overall, the appearance of the common alder includes a broad canopy with a straight trunk, bright green leaves that are sticky when new, conspicuous catkins and cones, and a bark that changes as the tree matures, making it a distinctive and beneficial component of the ecosystems it inhabits.
About this plant
NamesFamily
Betulaceae.
Synonyms
Black Alder, European Alder, Common Alder, Sticky Alder.
Common names
Betula alnus var. glutinosa, Alnus vulgaris, Alnus barbata, Alnus rotundifolia, Alnus glutinosa subsp. barbata, Alnus glutinosa var. vulgaris.
ToxicityTo humans
The common name for Alnus glutinosa is black alder. Black alder is not considered toxic to humans. There are no well-documented cases of poisoning from consuming the parts of the black alder plant.
To pets
Black alder is also not known to be toxic to pets. There are no significant reports of toxicity or poisoning in pets such as dogs and cats due to ingestion of any parts of the black alder plant.
CharacteristicsLife cycle
Perennials
Foliage type
Deciduous
Color of leaves
Green
Flower color
Yellow
Height
40-60 feet (12-18 meters)
Spread
20-30 feet (6-9 meters)
Plant type
Tree
Hardiness zones
3-7
Native area
Europe
Benefits
General Benefits- Erosion Control: Alnus glutinosa, commonly known as black alder, has an extensive root system that stabilizes riverbanks and prevents soil erosion.
- Nitrogen Fixation: Black alder has a symbiotic relationship with nitrogen-fixing bacteria, enriching the soil by adding nitrogen naturally, which benefits surrounding plant life.
- Wildlife Habitat: Its seeds, buds, and catkins provide food for various birds and small mammals, while the dense foliage offers shelter and nesting sites.
- Timber Production: Black alder is valued for its fast growth and is harvested for timber used in furniture, veneer, and plywood production.
- Flood Management: The tree's preference for wet conditions allows it to play a role in flood management by absorbing excess water in floodplains.
- Ornamental Use: It is sometimes planted for ornamental purposes in wet areas and is admired for its glossy dark green leaves and catkins.
- Stream Bank Stabilization: Black alder helps stabilize stream banks and is often used in riparian restoration projects to repair damaged stream ecosystems.
- Biodiversity: By supporting a range of insects and fungi, black alder contributes to the biodiversity of an area, fostering a balanced ecosystem.
- Woodland Creation: Ideal for creating or expanding woodlands, especially in damp or waterside areas where other trees might struggle to thrive.
- Phytoremediation: Black alder is used in phytoremediation projects to remove pollutants, like heavy metals, from the soil and water through accumulation in its tissues.
Medical Properties- Anti-inflammatory: Alnus glutinosa has traditionally been used for its potential to reduce inflammation.
- Astringent: The bark especially is thought to have astringent qualities, which can help with wound healing and skin conditions.
- Fever reducer: Historically, the plant has been used in folk medicine to reduce fevers.
- Diuretic: Some traditional uses include employing the plant as a diuretic to help with urinary tract issues.
- Sore throat remedy: Gargling preparations made from the leaves or bark have been used to soothe sore throats.
Air-purifying QualitiesThis plant is not specifically known for air purifying qualities.
Other Uses- Alnus glutinosa, commonly known as the common alder, has been used in the production of dyes, where its bark gives a reddish dye that can color fabrics and wool.
- The catkins of the common alder are used as a source of food for some moths and butterflies, providing ecological benefits for local insect populations.
- Its wood, being resistant to underwater rot, has historically been used for piles in the foundations of buildings in Venice and other waterlogged environments.
- The common alder’s wood is valued by woodworkers for turning on a lathe, giving a fine finish for items such as bowls, cups, and platters.
- The wood is also used to make clogs in some European cultures due to its durability and ease of shaping when green.
- Common alder is sometimes planted to stabilize riverbanks and prevent erosion, taking advantage of its strong root system.
- The tree has been used in landscape gardening as an ornamental plant, especially attractive for its glossy, dark green leaves and cones.
- The timber is suitable for joinery, creating frames and other structural elements, thanks to its good nailing and gluing properties.
- Common alder sawdust and chips are sometimes used in smoking fish and meats, imparting a distinct flavor.
- Alder trees can be coppiced, a traditional method in which trees are periodically cut down to ground level to stimulate the growth of straight shoots, which are used for poles and fencing materials.
Interesting Facts
Feng ShuiThe Alder tree is not used in Feng Shui practice.
Zodiac Sign CompitabilityThe Alder tree is not used in astrology practice.
Plant Symbolism- Protection: Alnus glutinosa, commonly known as Alder, is often associated with protection. In various cultures, it was thought to ward off negative energies and evil spirits.
- Strength and Resilience: The Alder tree's ability to thrive in wet conditions with strong root systems symbolizes the qualities of strength and resilience in the face of adversity.
- Guidance and Teaching: Alders, in some folklore, are linked to teaching and spiritual guidance, providing insight and enlightenment to those who seek knowledge.
WaterThe Black Alder requires consistent moisture and should be watered thoroughly whenever the top inch of soil feels dry to the touch. This typically means watering once a week with one to two gallons of water, depending on weather conditions and soil type. It's important to avoid waterlogging, so ensure that the soil drains well. During hot, dry periods, increase watering frequency to ensure the soil remains moist, but not saturated. Reduce watering in the winter when the tree is dormant.
LightBlack Alder thrives in full sun to partial shade, meaning it prefers a spot that receives at least four hours of direct sunlight daily. The ideal location would expose the Black Alder to sunlight for most of the day, but it can tolerate light shade. Avoid deep shade, as this can lead to reduced vigor and sparse foliage.
TemperatureThe Black Alder is a hardy tree that can withstand cold temperatures, with a minimum tolerance typically around -20 degrees Fahrenheit. It grows best in areas with moderate to warm temperatures, where the ideal range lies between 50 and 70 degrees Fahrenheit. The tree may struggle with temperatures above 80 degrees Fahrenheit for prolonged periods.
PruningBlack Alder should be pruned to maintain shape and remove any dead or damaged branches. Pruning is best done in late winter to early spring before new growth starts. This ensures the tree heals quickly and reduces the risk of disease infection. Prune sparsely, as excessive cutting can harm the tree. If necessary, young Black Alders can also be pruned to establish a strong central leader.
CleaningNot needed
SoilBlack Alder thrives best in moist, well-drained soil with a pH ranging from 5.0 to 7.0. A good soil mix for Black Alder would be a combination of loamy soil, sand, and peat to ensure adequate drainage while maintaining moisture.
RepottingBlack Alder, being a large tree, is not typically repotted. It's planted outdoors where it can grow freely without the need for repotting.
Humidity & MistingBlack Alder tolerates a wide range of humidity levels but prefers a moist environment, being commonly found near water sources in its natural habitat.
Suitable locationsIndoor
Growing Black Alder indoors is impractical due to its large size.
Outdoor
Plant Black Alder in moist soil and a sunny location.
Hardiness zone
4-7 USDA
Life cycleAlnus glutinosa, commonly known as the black alder, begins its life cycle as a seed which germinates in wet, marshy soils in the springtime. The sapling grows rapidly, favoring the damp environments of riverbanks and wet woodlands, and develops a symbiotic relationship with the nitrogen-fixing bacteria Frankia alni, which allows it to thrive in poor quality soils. As the tree matures, it forms a broad crown and produces catkins; the male catkins are long and yellow, while the female catkins are small, green, and eventually turn into woody cones after pollination. The black alder reaches reproductive maturity at around 12 years, when it starts to produce seeds that are dispersed by water due to their buoyant nature. In its mature phase, the tree can live up to 60 years, often providing stabilisation to riverbanks with its extensive root system. The black alder eventually dies, decays, and returns nutrients to the ecosystem, thus completing its life cycle.
PropogationPropogation time
Early spring
The most common name for Alnus glutinosa is the Black Alder, and it is typically propagated through seed collection and sowing. The best time to collect seeds is late autumn when the cones have dried and opened. Gathered seeds can be sown immediately or stored and then sown in the spring. To propagate by seed, seeds are scattered onto a well-prepared seedbed, which should be kept moist until germination occurs. Pre-treatment of seeds by stratification, which involves mixing seeds with moist sand and chilling them for approximately 1-2 months (at about 34 to 41 degrees Fahrenheit or 1 to 5 degrees Celsius), improves germination rates. Once the seeds germinate and the seedlings are large enough to handle, they can be potted in individual containers or planted in a nursery row for further growth before being transplanted to their final position.
