Magnolia kobus Seeds | Kobus Magnolia
LATIN NAME: Magnolia kobus
COMMON NAME: Kobus Magnolia, Kobushi Magnolia, Northern Japanese Magnolia
Plant Profile
Trees reach twelve to twenty metres in the wild, with a rounded crown, smooth grey bark and large oval leaves that emerge bronze and turn butter yellow before falling. Flowering is precocious, which in magnolias means buds formed the previous season expand before the foliage; each flower carries around nine tepals, the outer three shorter and sepal-like, the inner ones held wide in a shallow cup. The scent is slight and watery, carrying further in still mild air, and the base of the tepals is often flushed pink.
Few magnolias tolerate prolonged freezing as comfortably. Trees flower in spring where hard frosts still occur; open flowers are damaged, but the buds and wood survive, and the species grows fast when young. It is widely used as a rootstock for less hardy magnolias in northern nurseries for that reason, and a sheltered site delays flowering slightly, which is useful protection against a late cold night.
Magnolias evolved before bees, and this species still depends on beetles. The flowers are protogynous: the stigmas of a newly opened flower are receptive before the anthers in the same flower release pollen, so a beetle crawling in from another tree delivers pollen to receptive surfaces while a later arrival picks pollen up instead. The flower also generates heat for a short phase, raising its temperature above the surrounding air; the warmth volatilises the scent and gives beetles a reason to stay overnight inside a closing flower.
What looks like a cone is an aggregate of follicles, each derived from a separate carpel. When the follicles split, each seed hangs out on a slender elastic thread before it drops, and the seed is wrapped in a fleshy scarlet coat that birds find worth eating. The coat is the reward for dispersal; underneath it the kernel is hard and the embryo rudimentary, which is why the seed must be handled fresh and kept moist rather than stored dry.
Science & Biotechnology
Magnoliaceae chemistry is dominated by two groups. The first is the sesquiterpene lactones of the germacranolide class, represented in the family by costunolide and related skeletons, and by the volatile terpenoids released by flowers and crushed leaves. The second is the neolignans, the group that includes magnolol and honokiol; those two compounds are characteristic of the East Asian medicinal magnolias whose bark is used in pharmacy, and they are not the reason this species is grown. Screening work across the genus has sampled many species for both classes of compound, and the bark of the kobus magnolia has been examined in that comparative context rather than as a drug source.
Uses & Benefits
In Japan the tree grows in cool moist deciduous woodland, often on slopes and along valley edges with oaks, birches and maples. It reached European gardens in the nineteenth century through the Japanese collections of Philipp Franz von Siebold, though Japanese gardeners had planted it for centuries as a roadside and garden specimen. The pale, soft timber has been worked in Japan into light joinery and small carved items.
Growing from Seed
As a garden tree it is best given room as a specimen on a lawn or at the corner of a woodland garden, where the bare spring wood has a dark background behind it. Japanese planting uses it in loose avenue rows and beside gateways. Branches cut when the first flowers open last well indoors, a use that has made it a favourite of florists in Japan, and the flowers are visited by early bees and beetles, though they offer pollen rather than nectar.
Prepare a hole wide enough for the roots to spread without bending, and backfill with three parts loam, two parts leafmould and one part grit; magnolia roots are fleshy and resent a dry compacted pocket. Set the plant no deeper than it grew in the nursery, firm gently, water, and mulch with leafmould kept clear of the trunk. Space specimen trees about six metres apart and allow eight for an avenue. Young trees want even moisture through their first summers; a light dressing of a balanced fertiliser in early spring is enough, since heavy feeding produces soft growth that frost damages. Prune only dead or crossing branches, straight after flowering, because magnolias bleed from cut wood and heal slowly; never cut into old limbs to reduce size, as the tree does not replace them readily.
Clean the scarlet coat off as soon as the follicles open, wearing gloves, because the flesh attracts rodents and can hold the seed back when left in place. Sow at once into a deep pot of loam, leafmould and grit, covering the seed with about a centimetre of the mix, and leave the pot outside in a shaded frame to take the winter cold. The root develops long before the shoot, so a pot may show nothing above the surface for a full season while the lower half is working. Keep the mix damp and never let it dry completely.
Our Take
If you have lost a magnolia to winter, plant this one and start again. I set it where the first flowers can be seen from a window, with the white yulan magnolia a little further along the same boundary for a later, larger bloom, and a deep purple lily magnolia behind it to carry the season on. Where there is space for only one, the saucer magnolia is the showier choice, but it will not take the cold that this species shrugs off.
Related Reading
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