Siebold magnolia has grown well at Mustila and elsewhere in southern Finland when it has been planted in rich soil in semi-shade. Its native habitat is in eastern Asia, in particular among shrubbery on volcanic soils.
The species flowers in Finland after Midsummer when in full leaf, and can sometimes flower a second time in late summer. The blossoms are about 10 cm in diameter, usually drooping and not quite fully open so that to get a close look at detail they must be looked at from below. The Korean form (var. sieboldii) is most commonly grown, with attractive red stamens and a yellow pistil surrounded by white petals. The old shrubs of Alppiruusulaakso (Rhododendron Valley) and the western side of Etelärinne (Southern Slope) represent this form.
Siebold magnolia is considered the hardiest of the magnolias grown in Finland and in the right spot is hardy to Finnish zone III. However, there seems some variation in hardiness depending on provenance, and this species is among the most demanding of the genus with regard to the tenderness of its roots and foliage.