The elegance and beauty of the star magnolia are a welcome sign of spring. The intricate and colorful star magnolia flowers appear weeks ahead of other spring flowering shrubs and plants, making this tree a popular choice as a focal tree for early spring color.
I. Appearance and CharacteristicsÂ
Magnolia stellata, the star magnolia, is a slow-growing deciduous shrub or small tree native to Japan. It bears large, showy white or pink flowers in early spring, before its leaves open. This species is closely related to the Kobushi magnolia (Magnolia kobus), and is treated by many botanists as a variety or even a cultivar of that. However, Magnolia stellata was accepted as a distinct species in the 1998 monograph by Hunt.
The species Magnolia stellata may be found growing wild in certain parts of the Ise Bay area of central Honshū, Japan’s largest island, at elevations of 50 to 600 m (160 to 1,970 ft). It grows by streamsides and in moist, boggy areas with such other woody plants as Enkianthus cernuus, Corylopsis glabrescens var. gotoana and Berberis sieboldii.
This shrub grows 1.5 to 2.5 metres (5 to 8 ft) in height, spreading to 4.6 m (15 ft) in width at maturity. Young plants display upright oval growth, but the plants spread and mound with age.
M. stellata blooms at a young age, with the slightly fragrant 7–10 cm (3–4 in) wide flowers covering the bare plant in late winter or early spring before the leaves appear. There is natural variation within the flower color, from white to rich pink; the pink also changes from year to year. The flowers are star-shaped, with at least 12 thin, delicate petal-like tepals, some cultivars having more than 30.
The leaves open bronze-green, turning to deep green as they mature, and yellow before dropping in autumn. They are oblong and about 10 cm (4 in) long by about 4 cm (1.6 in) wide.
M. stellata produces a reddish-green, knobby aggregate fruit about 5 cm (2 in) long that matures in early autumn. Mature fruit opens by slits to reveal orange-red seeds, but the fruits often drop before developing fully.
Young twigs have smooth, shiny chestnut brown bark, while the main trunks have smooth, silvery gray bark. Like the saucer magnolia (Magnolia × soulangeana), it is deciduous, revealing a twiggy, naked frame in winter. Plants have thick, fleshy roots which are found fairly close to the surface and do not tolerate much disturbance.
II. How to Grow and Care
Sunlight
This tree grows best in full or partial sun, needing at least four hours of direct, unfiltered sunlight daily.
Temperature and Humidity
Star magnolia is cold hardy down to zone 4 or as cold as -30 degrees Fahrenheit. However, it can be damaged by heavy snow and ice, particularly its blossoms can be injured by frost or wind. Its humidity needs are moderate, at about 30 to 50 percent.
Watering
Star magnolia is a relatively drought-tolerant plant but will perform best when watered regularly. During very long periods of drought, it should be watered more frequently. The best time to water your plants is when the top few layers of soil are dry. Star magnolia doesn’t tolerate waterlogged soil.
Soil
Star magnolia likes to grow in loamy, well-draining moist soil. The plant can grow in both neutral and acidic soils.
Fertilizing
Star magnolia is considered a light feeder and may benefit from occasional fertilizing. Feed each spring with a slow-release fertilizer designed specifically for shrubs and trees. Potted plants may need more frequent feeding—fertilize them with liquid fertilizer several times during the active growing season. In late winter, you can also apply a layer of manure, garden compost, or organic fertilizer.
Pruning
The plant blooms on old wood (last year’s growth), so prune it more or less immediately after blossoming to avoid losing next year’s flowers. People don’t generally prune magnolias much (although M. stellata is sometimes a bit more tolerant of pruning than other members of its genus).
They have a tendency to grow as multi-stemmed shrubs or bushes. If you wish to avoid this look, prune away any suckers to train your specimen to assume a tree form. Prune away the lower growth as it emerges while letting the rounded, spreading crown become dense.
New growers are sometimes alarmed by the “funny growths” that appear on star magnolia trees in the latter part of the growing season. No need to worry, though: Those odd lumps are just the pods in which star magnolia tree seeds are contained.
Propagation
The best way to propagate star magnolia is by stem cuttings in late spring or early summer from soft or semi-hardwood. If using a rooting hormone, roots will grow in a few weeks. Star magnolia can also be grown from seed.
You will need to grow the rooted cutting in a pot for a year under controlled conditions before planting it in the ground. Using stem cuttings from annual pruning benefits star magnolia when branching gets crowded. Here’s how to propagate a star magnolia using stem cuttings:
- You will need a planter or pot with drainage holes, a perlite potting mixture, sterilized pruners or a knife, and a clear plastic bag. Optionally, get compost and rooting hormone.
- Cut a 6- to 8-inch branch with active growth, cut on a diagonal, or cut a vertical slit at the bottom. Optionally, add rooting hormone to the cut end to encourage rooting success.
- Plant the cut end about 2 inches deep into the perlite potting mix. Optionally, add compost to the mixture to encourage growth. Moisten the soil. Tent a clear plastic bag over the planter to trap moisture in the bag, which encourages rooting.
- Put the plant in indirect light. While waiting for roots to grow, keep the top of the soil moist. Remove the tented bag once you notice growth—a sure sign of successful rooting.
How to Grow from Seed
Magnolia seeds must go through stratification or a cooling period to germinate.
- Place the seeds in a container of moistened sand in the refrigerator for three months. When you remove the seeds from the cold, it triggers the seeds to germinate.
- Plant the seeds about 1/4-inch deep in a pot or the ground in the spring using potting soil. Mulch over the plant to keep moisture in the soil. Place it in a sunny spot.
- Transplant the seedling after about one year of continuous growth in a controlled environment. The planting hole should be at least three times the width of the root ball or container and just as deep.
- The root ball should be even with the ground when placed in the hole. Be sure the plant is straight before replacing half of the soil you took from the hole.
- Fill the hole with water and allow the root ball to absorb the moisture. Backfill the hole with the remaining soil.
- Top dress with a layer of mulch to keep the roots moist and discourage weed growth. Dress with compost in late winter.
Pests and Diseases
Common Pests and Plant Diseases
Star magnolias are susceptible to fungal infections like powdery mildew, botrytis (gray mold), verticillium wilt, and leaf spot. It spreads by spores between infected plants.
To prevent conditions that favor fungal growth, give the plant ample sunlight, air circulation, and well-draining soil, and make sure the tree has dry foliage and flower petals. Also, remove infected leaves early on. Prune branches or thin them out to discourage an overly moist environment and promote air circulation. If symptoms persist, treat with fungicides according to the product label instructions.
Magnolia scale insects are one of the biggest threats to star magnolias. The insects suck the sap from the leaves and can harm the tree. The insects leave behind a residue that leaves a black, sooty mess, which encourages mold growth conditions.
To treat the magnolia scale, you must catch it early on when the insect is in the crawling stage. You can use organic methods like horticultural oil or insecticidal soap (usually applied in August) and reapply again two weeks later. Progress to other chemical alternatives if organic methods are unsuccessful.
Common Problems With Star Magnolias
Star magnolias are easy to plant, and their care is straightforward. They are relatively trouble-free, except for being susceptible to fungus and scale if the branches are overcrowded or not getting enough ventilation.
Tiny Brown or White Bumps on Branches
A sign of star magnolia infested by magnolia scale is brown or white bumps clustering on branches. The plant’s leaves appear shiny and sticky and often look like they have black sooty mold growing on the plant. If not treated or the insects overtake the plant, the tree will not survive. To get rid of magnolia scale, manually remove the insects or the affected limbs or branches, or use organic or chemical controls like horticultural oil, insecticidal soap, or pesticides.
Brown or Black Leaf Spots
Several fungus types can cause leaf spots that appear black, brown, tan, or red. Leaf spot is most likely to occur during rainy or humid weather and often clears up when sunny, dry weather returns. Remove diseased brown leaves that have dropped, preventing the fungus from spreading. Most mature trees can fight it independently, but a young tree might need help from a copper-based fungicide before being ravaged by the fungus.
Dying Branches
Verticillium wilt is a fungus that can kill branches or an entire star magnolia. Symptoms include streaking and fading wood, leaves dropping prematurely, and weakening limbs. Once a plant gets verticillium wilt, spores remain on the tree, infect the soil, and can spread. Mature trees can likely fight it off for a few years, but the prognosis is grim; eventually, it will kill the tree. Removal is the best course of action.
III. Uses and BenefitsÂ
Star magnolia (Magnolia stellata) is a popular standout ornamental shrub that graces gardens with extremely showy white flowers in early spring. The small size of this shrub makes it a great candidate for smaller gardens, but it also suits a variety of other garden styles as well. Star magnolia also looks great when grown as a specimen in containers or on patios. Set off the plant’s white flowers with bright geraniums or sages.
