Garden hybrids between M. baccata and M. halliana, intermediate between the parents. The type form makes an upright, round-headed tree. Up to 8 flowers per inflorescence; pedicels glabrous. Flowers semi-double with 5–15 petals, pale pink from pink buds, ageing white, to 5 cm diameter; calyx hairy, especially above, falling before fruit is ripe. Fruits yellow-green blushed red, to 1.5 cm diameter. (Fiala 1994; Jacobson 1996; Edwards & Marshall 2019).
RHS Hardiness Rating H6
Described as ‘delightful’ (Edwards & Marshall 2019) and ‘overlooked’ (Fiala 1994), this old primary hybrid is desirable for its abundant, very large, semi-double flowers with red calyces and pedicels, and its persistent fruit. Reports of disease susceptibility vary widely (Fiala 1994; Jacobson 1996); Nick Dunn (pers. obs. 2020) considers it disease resistant in the UK.
Malus × hartwigii was described from a specimen received by Karl Gustav Hartwig from the Vorwerker nursery, Lübeck, Germany, where it had long been grown; it may have originated in Holland (Koehne 1906). Not a common tree, there is an example at Kew, planted in 1958 (6 m × 98 cm, 2010 – The Tree Register 2020). It is recorded from the Hof ter Saksen Arboretum, Belgium, and the Belmonte Arboretum, Netherlands (Plantcol 2020, Belmonte Arboretum 2020). Jacobson (1996) considered it ‘extremely rare’ in North America; there are examples in Washington Park, Seattle and at the Arnold Arboretum (University of Washington Botanic Gardens 2020, Arnold Arboretum 2020).
The cultivar ‘Katherine’ (see ‘Cultivars J-K’) probably has this parentage (Fiala 1994).