Alnus glutinosa
Environmental Weed (2024)
Common names
common alder
Biostatus
Exotic
Category
Vascular
Structural class
Trees & Shrubs - Dicotyledons
Simplified description
Widespread, especially common in the Waikato and Wairarapa, where it can be a problem weed.
Flower colours
Violet/Purple, Yellow
Detailed description
Tree to c. 15m high (to c. 20m in cultivation). Bark dark brown, strongly fissured. Young shoots glabrous but glandular-viscid. Winter buds shortstalked, purplish. Petiole 7-15 mm long, often purplish. Lamina 4-10 x 2.5-10cm (to 14 x 13cm on vigorous vegetative shoots), broadly oblong to obovate, plicate in bud, hairy on veins beneath at first, soon glabrous except for tufts axillary hairs, serrulate to coarsely serrate, lobulate on basal vegetative shoots; veins in 6-7 pairs, prominently raised beneath; base usually cuneate; apex rounded to retuse. Buds stipitate, not enclosing female catkins in winter. Male catkins 3-8 together behind shoot apices, 2.5-7cm long (to 12 cm in cultivation), cylindric, opening in spring before lvs; peduncles to c. 5 cm long; bracts peltate, purplish; anthers yellow. Female catkins 3-7 together behind shoot apices, c. 5mm long, glandular. Cone (1)-1.3-1.7-(2) cm long, ellipsoid; scales becoming horizontal after dehiscence and persistent on tree. Nutlet c. 3mm long, broadly ovoid; wing narrower than nut.
Similar taxa
No similar tree in that habitat.
Distribution
Widespread, especially common in the Waikato and Wairarapa, where it can be a problem weed.
Habitat
Riparian areas along rivers and lakes.
Conservation status
Not applicable
Detailed taxonomy
Genus
Family
Ecology
Flowering
Late winter to spring
Fruiting
Summer
Year naturalised
1914
Origin
Europe, Asian and North Africa.
Reason for introduction
Ornamental and timber tree also produces a yellow dye.
Tolerances
The plant prefers moist a situation and has been planted in colder areas (Webb et. al., 1988).
Control techniques
Can be controlled mechanically or herbicidally depending on situation.
Life cycle and dispersal
Perennial. Wind and water dispersed seed, also forms thickets by suckering. Fruiting is prolific (Webb et. al., 1988).
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
FACW: Facultative Wetland
Usually is a hydrophyte but occasionally found in uplands (non-wetlands).
Other information
Etymology
alnus: From an old Latin name for alder
glutinosa: From the Greek gloeo ‘glue’, refers to the gummy leaves
Environmental Weed (2024)
This plant is named in a list of 386 environmental weeds in New Zealand 2024 prepared by DOC. 759 candidate species were considered for inclusion on this new comprehensive list of environmental weeds in New Zealand. The species considered were drawn from published lists of weed species, lists of plants that must be reported or managed by law if observed, existing national and regional programmes and agreements for pest management, and species already managed by the Department of Conservation (DOC). Candidate species were then assessed to see if they were fully naturalised and whether they have more than minor impacts in natural ecosystems. Read the full report here.
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
ALNGLU
Referencing and citations
References and further reading
Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. (1988). Flora of New Zealand Volume 4: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch.
Popay et al (2010). An illustrated guide to common weeds of New Zealand, third edition. NZ Plant Protection Society Inc, 416pp.
Johnson PN, Brooke PA (1989). Wetland plants in New Zealand. DSIR Field Guide, DSIR Publishing, Wellington. 319pp.
Attribution
Prepared by Paul Champion and Deborah Hofstra (NIWA). Features description and life cycle and dispersal and tolerances information from Webb et. al. (1988).