Magnolia stellata (Sieb. & Zucc.) Maxim.

Well known across much of our area, the Star Magnolia combines cold hardiness and a compact habit suiting smaller gardens with profuse, many-tepalled white flowers on bare twigs late enough in spring usually to avoid frost damage. Within a few decades of its introduction Bean (1914) could claim it as the most desirable of all magnolias for small gardens, and recommended underplanting it with blue Muscari armeniacum, which flowers at the same time. Its abundance in suburban gardens contrasts sharply with its wild status in Japan, where it is a very local rarity.

Much more shrubby than its Japanese relatives M. kobus and M. salicifolia, it typically forms a dense, twiggy bush, quite slow growing but sometimes as much as 6 m tall in gardens. It is not difficult to prune an established shrub to form a small, spreading, multistemmed tree, by removing all but selected stems near the base, and raising the crown. Its flowers, with more numerous, narrower tepals which tend to flop outward to make a loose star (hence the specific epithet), easily distinguish it from these other species.

Wild M. stellata exists as many small, scattered populations at fairly low altitude in the Nagoya area, mostly in swampy ground and along streams. While there seems have been gene flow between these populations in the past, it has declined (Setsuko et al. 2007). Conservation measures include clear-cutting the habitat periodically to avoid drying of the wet areas favoured by M. stellata, and to encourage its regeneration; in the past, management for firewood production probably had this effect (IUCN 2021).

Slightly fragrant flowers open in succession over a number of weeks from late March to early May, depending on site, situation, and clone. Since the species has been cultivated in Japan for centuries, diversity in flower size, tepal number, and colour can be expected. Flowers vary in size between 7 and 10 cm across, although a vigorous American selection has produced flowers as much as 12.5 cm across. Tepal number varies enormously, anything from 12 to 40. The colour is generally white or cream, though a number of forms have a pink flush, especially when the flower first opens. Blooms withstand several degrees of frost before discolouring. Vegetatively propagated plants can flower from 18 months old.

M. stellata needs a moisture-retentive soil in a sunny position for best flowering. Acid soils are ideal, but it tolerates alkaline soils given regular mulching. It is quite hardy, usually being regarded as suitable for USDA zone 5. Some forms have a still greater frost tolerance – ‘Royal Star’, for example, is reported to have withstood temperatures as low as –37.2°C.

The first confirmed introduction to Western gardens was in 1861–2 by George Hall of Rhode Island (commemorated in the synonym M. halliana), on his return from a period spent on business in the Far East. He passed it into the American nursery trade. It is uncertain when M. stellata first came to Europe. It has been variously suggested that John Gould Veitch of the English nursery dynasty, or Richard Oldham (a collector employed by Kew) sent plants to England in the early 1860s. More certainly Charles Maries, collecting for Veitch, introduced it along with M. kobus in the 1870s.

While still very hardy by the standards of the genus, M. stellata with its narrow, low altiude range cannot match the cold tolerance of the toughest forms of M. kobus. Commonplace in Western Europe, it is recorded as far north as Trondheim, Norway (NTNU University Museum 2021). However, in Poland spur shoots, flower and vegetative buds may be killed in severe winters (Anisko & Czekalski 1991), while a discussion of magnolias in southern Finland, where only the tougher forms of M. kobus are successful, makes no mention of M. stellata (Arboretum Mustila 2021).Usually rated as hardy to USDA zone 5 (sometimes even to zone 4) it is commonly grown in much of the United States, away from very cold north-central and dry regions, as well as in southern Canada.

There seem to be no barriers to breeding between M. stellata and M. kobus; the hybrid M. × loebneri is well known from garden crosses, but also occurs where M. kobus is introduced into the wild range of M. stellata, a potential genetic threat to the species (Tamaki et al. 2021). It also hybridizes with M. salicifolia to produce M. × proctoriana, and has been used more widely by hybridists.

Very many cultivars have been selected, especially pink flowered, although their status as the pre-eminent small-garden magnolias is now severely challenged by the best M. × loebneri cultivars.