Star Magnolia, Magnolia stellata

Star magnolia trees in bloom.

Star magnolia trees in bloom.

Star magnolia (Magnolia stellata) is one of the smallest magnolias, producing a showy cloud of white flowers in early spring. Originally from the highlands of the Japanese island of Honshu, it is sometimes considered a variety of M. kobus but of garden origin.

M. stellata was introduced to the United States in the 1860’s. It is variously listed as hardy from either zone 4 or 5 to 9. The specimen in my garden on the edge of zones 4 and 5 has flourished for over 25 years.

The silvery gray bark on a main trunk (L) and a multi-branched trunk (R).

The silvery gray bark on a main trunk (L) and a multi-branched trunk (R).

This slow growing deciduous plant can be grown as a large shrub or pruned up as a small multistemmed tree. It eventually reaches a height of 15-20 feet with a rounded crown spreading to 10-15 feet when mature. Young plants have a more upright, conical habit. It is denser and more compact than saucer magnolias, with a heavily branched, twiggy structure for winter interest, along with attractive smooth, silvery gray bark on the main trunk and shiny chestnut brown bark on the young twigs.

Flower buds just before opening.

Flower buds just before opening.

The fat, fuzzy buds open in late winter before the foliage appears to produce clusters of lightly fragrant, 3-4 inch white flowers. The blooms have 12-18 thin, delicate, strap-like petals; some cultivars have more than 30 petals per flower. The flowers need shelter from frost and wind which discolor the blooms. The plant creates a spectacular show when covered in blossoms, with flowers from the top of the plant to the lowest branches. Even very small plants are likely to bloom. They flower just before saucer magnolia blooms.

Different clones or cultivars have different numbers of petals.

Different clones or cultivars have different numbers of petals.

Later in the season the plant produces attractive fruit and seeds. The large seeds grow within a bright pink, knobby capsule 2-3 inches long. Many of the fruits drop before they are fully developed, but those that remain on the tree burst open in early autumn to reveal brilliant orange seeds.

Magnolia stellata with fruits (L), an intact knobby pink fruit capsule (C), and burst capsule with orange seeds (R).

Magnolia stellata with fruits (L), an intact knobby pink fruit capsule (C), and burst capsule with orange seeds (R).

The oblong leaves are about 4 inches long. They emerge with a bronze cast, are a clean medium to dark green in the summer, and turn yellow to bronze in the autumn, but do not make a particularly nice fall color display.

Star magnolia in early bloom.

Star magnolia in early bloom.

Star magnolia does best when planted in moist, organic, acid soil in full sun, but is relatively adaptable (it’s done fine in our heavy clay soil). If possible, plant in a protected area to prevent buds from opening early and then being killed by a late frost or freeze. This shrub generally does not need any pruning – unless you wish to train it to a tree shape. Pruning should be done after flowering to avoid cutting off buds set for the next season.

Star magnolia is a great flowering tree in a small yard since it remains small and compact for many years. It makes a good specimen plant, but can also be incorporated with other trees and shrubs into a planted bed. It is particularly nice when sited against a dark background, such as a brick wall or grouping of evergreens, which shows off the flowers, or on or near a patio where the scent of the flowers can be enjoyed. It also makes a good addition to the edge of woodland gardens or other partly shady areas.

M. stellata Royal Star tree in late winter.

M. stellata ‘Royal Star’ tree in late winter.

Star magnolia is a relatively trouble-free plant. It is soft-wooded, however, so may be damaged by heavy snow and ice. Also, the blossoms are susceptible to injury by frost or wind. Magnolia scale is about the only reported insect pest. Infested plants have shiny sticky leaves, often with black sooty mold growing on the honeydew produced by the adult females that look like brown buds on the twigs. Heavily infested plants can be more prone to winter kill problems. Apply insecticide treatments in early September to kill the susceptible crawler stage when they are out on the new growth (look for small flat insects on leaves and stems).

Star magnolia may be propagated by taking cuttings in early to mid-summer or from seed. Some sources indicate germination is slow and seeds require special handling, but there is never a shortage of seedlings under the tree planted in my yard! (I’ve only weeded them out, never tried to transplant and nurture them.)

Star magnolia has variable flowers.

Star magnolia has variable flowers.

There are many horticultural cultivars that are preferable to the species. Some of the most commonly available include:

  • ‘Centennial’ was released by Harvard’s Arnold Arboretum to commemorate the institution’s 100th anniversary in 1972. The large (5½ inch), many-petaled flowers are white with a slight tinge of pink on the outside, while the upright plant with a central leader reaches 25 feet tall.
  • ‘Jane Platt’ has flowers with many light pink tepals that open to white. The tree grows 10-20 feet tall.
  • ‘Pink Stardust’ produces numerous large, fragrant flowers (4-5″) on a pyrimidal tree to 12 feet tall.
  • ‘Rosea’ includes several light pink-flowered clones. The flowers fade to white at maturity and are not fragrant.
  • ‘Royal Star’ is possibly the best and is quite common in commerce. It produces abundant, double, snow-white flowers with 25-30 petals each from pink buds. It grows 10-12 feet tall.
  • ‘Rubra’ has purplish rose flowers that fade to pink. The compact shrub has yellow-green leaves.
  • ‘Waterlily’ includes several clones under this name. Their flowers have larger, narrower, more abundant petals. The pink buds open to highly fragrant flowers. It is a bushy, upright grower that may flower slightly later than other cultivars.

– Susan Mahr, University of Wisconsin – Madison


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6 comments

  1. I have a star magnolia that was purchased from Wayside Gardens when they were in Ohio in the early 1970’s. I truely believe it must be the largest specimen in the state of Maryland. How may I post a picture? This tree has a measured spread over 40 feetand a height in excess of 35 feet. The trunk before it branches is no less than 8 feet in circumference.

  2. My magnolia stellata trono is turning yellow ,do I need to worry? I live outside Toronto Canada.hope you can help.
    Thank you

  3. I have had to cut my star magnolia tree down to the ground hoping that it will be able to be shaped into a shrub instead. Now it’s growing like gangbusters and the leaves are huge and there are just too many sprouts. How do I cut it the right way. One vineyard mgr said I could thin out the sprouts and go from there but that seems too sloppy. Is there a right way to do this or have I ruined the shrub? any advice appreciated.

    • Contact your local Extension office and they can advise you on the best method and timing for your area.

  4. I have read a lot of negative comments about pruning a Royal Star Magnolia. But I have one that has become quite misshapen, due to the unfortunate teething habits of a young dog. The plant is approximately 6 years old and stands approximately 4 feet high. It’s sister plant is approximately 4 feet round. This one is not nearly as full, as Murphy chose this one to teeth on. So it is much fuller at the top than it is on the bottom where he was able to chew on the branches. It is quite unsightly. I have never done any pruning on these trees, and I think I might like to train it more into a tree specimen as opposed to a bush. But looking at the main trunk structure it appears to have two or more main trunks that come right to the ground. When I originally planted these bushes, I did not research fully and was not aware they would get as big as I am now reading. And I planted them is specimen pieces in a large garden. I’m afraid they will get too large if left in Bush form and make the garden look sloppy. And everything I have read indicates that I should not try to make it conform to the size and shape I want, but rather let it do its own thing. I would appreciate any suggestions in making my “teeth ring” back into a beautiful bush.

    • The bottom will likely fill out in time; I have to hack back mine every year as it is too close to the walkway, and every year it is just as full and dense as the previous year. Now we are going to take off the bottom to have it more as a tree than giant shrub. It is multi-trunked, but will look just fine that way. You can go either route with yours, thinking in terms of maintenance down the road. Our 30 year old tree is probably 25 feet across; do you want to have to keep pruning it every year to keep in a smaller space as a shrub, or prune it up and let it grow over the area as a tree? I would recommend pruning it either way to shape it as it grows and to promote denser growth. Be sure you are cutting back to just above a healthy bud or side branch, without taking too much off at any one time (unless it is diseased or damaged). The best time to prune is in late winter, but early summer pruning is ok (don’t prune when the foliage is wet to reduce disease problems). Don’t prune in late summer, or the tree will direct its energy into new growth instead of hardening off for the upcoming winter.

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