Salix fragilis × S. euxina
NPPA pest plant
Environmental Weed (2024)
Common names
crack willow
Biostatus
Exotic
Conservation status
Not applicable
Category
Vascular
Structural class
Trees & Shrubs - Dicotyledons
Simplified description
Deciduous tree up to 25 m tall, branches not drooping but breaking easily, often with an audible crack (hence the common name), leaves narrow and lance-shaped, often with bright red swellings on them, flowers produced in spring about the same time as emergence of leaves, with long and narrow (up to 7.5 cm long and 1 cm across) yellow green in colour.
Flower colours
Green
Detailed description
Tree to 25m high, sometimes only a shrub; bark rough and fissured. Branches spreading but not pendulous. Shoots dark or brownish green, readily and audibly snapping when bent, not slender. Bud scales dark shining brown, becoming glabrous. Shoots and leaves somewhat silky when very young, but quickly glabrous. Petiole of leaves on reproductive shoots < 1cm long. Lamina 5–15 x 1–2.5cm, sometimes larger on water shoots, lanceolate, glaucous beneath, mainly shining above, glandular-serrulate; apex acuminate. Stipules minute. Catkins usu. male, rarely female, appearing with or after leaves. Male catkins 4–7.5cm long, spreading or curving downwards, narrow-cylindric; rachis villous. Bracts 2–2.5mm long, oblong-elliptic, incurved and generally cucullate when fresh, pale green or yellowish, densely clothed in antrorse hairs; apex rounded. Glands 2, 0.4–0.6mm long, elliptic-oblong, rectangular to square. Stamens 2; filaments hairy towards base. Female catkins similar to male. Ovary glabrous, sessile or shortly stalked.
Similar taxa
Similar to other lanceolate leaved willows, but can be distinguished by the brittle green to reddish brown (rather than yellow) shoots, spreading rather than drooping branches and red galls on leaves.
Distribution
Widespread and often abundant throughout New Zealand.
Habitat
Riparian margins of water bodies.
Detailed taxonomy
Genus
Family
Synonyms
Salix alba L. × S. euxina I.V. Belaeva; Salix fragilis L.; Salix ×rubens Schrank
Taxonomic notes
Recently recognised as a hybrid in Belyaeva, I. (2009) Nomenclature of Salix fragilis L. and a new species, S. euxina (Salicaceae). Taxon 58(4): 1344–1348. The hybrid between this entity and Salix alba = S. ×rubens is now included in the taxon S. ×fragilis as a synonym.
Ecology
Flowering
September to October
Fruiting
Europe and West Asia
Year naturalised
1880
Origin
Europe, Western Asia
Reason for introduction
Erosion control for rivers and other waterways
Tolerances
The plant is intolerant of shade and highly tolerant of poor drainage. Physical damage and grazing result in resprouting.
Control techniques
Can be controlled manually, mechanically or herbicidally depending on situation.
Life cycle and dispersal
Stem fragments dispersed by water and contaminated machinery.
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
National Pest Plant Accord species
This plant is listed in the 2020 National Pest Plant Accord. The National Pest Plant Accord (NPPA) is an agreement to prevent the sale and/or distribution of specified pest plants where either formal or casual horticultural trade is the most significant way of spreading the plant in New Zealand. For up to date information and an electronic copy of the 2020 Pest Plant Accord manual (including plant information and images) visit the MPI website.
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.
Manaaki Whenua Online Interactive Key
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.
Belyaeva, I.V. (2009). Nomenclature of Salix fragilis L. and a new species S. euxina (Salicaceae). Taxon 58(4): 1344-1348.
Attribution
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA). Features description from Webb et. al. (1988).