Alnus × spaethii Callier

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Credits

Tim Baxter & Hugh A. McAllister (2024)

Recommended citation
Baxter, T. & McAllister, H.A. (2024), 'Alnus × spaethii' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/alnus/alnus-x-spaethii/). Accessed 2024-05-28.

Genus

  • Alnus
  • A. japonica × A. subcordata

Glossary

acuminate
Narrowing gradually to a point.
acute
Sharply pointed.
clone
Organism arising via vegetative or asexual reproduction.
dbh
Diameter (of trunk) at breast height. Breast height is defined as 4.5 feet (1.37 m) above the ground.
hybrid
Plant originating from the cross-fertilisation of genetically distinct individuals (e.g. two species or two subspecies).
ovate
Egg-shaped; broadest towards the stem.

Credits

Tim Baxter & Hugh A. McAllister (2024)

Recommended citation
Baxter, T. & McAllister, H.A. (2024), 'Alnus × spaethii' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/alnus/alnus-x-spaethii/). Accessed 2024-05-28.

A hybrid between A. japonica and A. subcordata which originated at the Späeth nurseries of Berlin in 1894 and entered the trade in 1908 (Bean 1976). The name Alnus × spaethii refers to any hybrid of this parentage, but Späeth selected a single clone for release from the original batch of seedlings which is generally listed as a cultivar, ‘Spaeth’, to avoid conflict with other occurences of the same hybrid (Jablonski 2018; Hatch 2021–2022).

Späeth’s original clone forms a distinctive, hardy tree with a uniformly upright oval crown to 20 m or more with elliptic-ovate leaves which are violet-purple when young and purple-red in autumn; it is also notable for its large and remarkable catkins which give long-lasting winter interest. It is most easily distinguished by the foliage: the leaves are similar in outline to those of Alnus japonica which are elliptic-ovate with acute to acuminate tips, but much larger than those of most cultivated A. japonica, similar in this regard to A. subcordata (De Langhe 2022). As noted in Grootendorst (1972) this hybrid was highly rated in trials held at Boskoop, the Netherlands, and remains one of the best alders for general planting. It is a fast-growing tree capable of attaining about 15 m in fifteen years in optimal conditions, and has been extensively planted as an amenity tree including as a street tree (Clarke 1988). Although at its best in wetter conditions A. × spaethii can tolerate periodic drought; it can be propagated by summer cuttings. The largest tree on record measured 25 m × 1.12 m dbh in 2019, growing at Ryston Hall Park in Norfolk, UK (monumentaltrees.com).


'Spaeth'

The original form of the cross distributed by Späeth from 1908, discussed in the main text above.