Magnolia kobus

kobus magnolia

Attracts Pollinators Deer Resistant Drought Tolerant Fragrant (light)

SunFull Sun – Part Shade

HardinessZones 4–8

Overview

Magnolia kobus is a medium to large deciduous tree reaching 25–40 feet (7.5–12 m) tall in cultivation — to 75 feet (23 m) in native habitat — and 25–35 feet (7.5–10.5 m) wide, with a broadly pyramidal crown that rounds out with age. The species is native to Japan and Korea and carries USDA zone 4 cold hardiness, tolerating sustained winter temperatures to –30°F (–34°C). Flowers are 3–4 inches (8–10 cm) across, white, with 6 tepals plus 3 smaller sepal-like outer tepals, lightly fragrant, borne on bare branches from late March through April over a 2–3 week window. Seedling trees reach flowering maturity at 10–15 years; grafted specimens flower sooner at 3–5 years. Leaves are alternate, obovate, 3–6 inches (8–15 cm) long, medium to dark green, emerging after the flowers fade. Bark is smooth and gray on young trunks, developing shallow furrows with age. Growth rate is moderate at 12–18 inches (30–45 cm) per year, reaching mature size in 20 years. The species is widely used as rootstock for grafting other magnolia cultivars and is a parent species in the crosses that produce M. x loebneri and M. x kewensis. Not known to be toxic to pets or humans.

Native Range

Magnolia kobus is native to Japan (Honshu, Hokkaido, Kyushu, Shikoku) and Korea, occurring in temperate deciduous forests, mountain slopes, and stream valleys from sea level to 4,000 feet (1,200 m) elevation.

Suggested Uses

Used as a specimen tree, shade tree, or rootstock plant in medium to large gardens at 25–30 foot (7.5–9 m) spacing. Zone 4 cold hardiness extends magnolia plantings into colder regions than most species in the genus. Flowers are 3–4 inches (8–10 cm) — smaller than garden hybrids such as M. x soulangeana at 4–6 inches (10–15 cm) and M. 'Iolanthe' at 8–10 inches (20–25 cm). The long juvenile period from seed makes grafted plants the typical nursery form for landscape plantings. Beyond landscape use, the species is widely employed as rootstock onto which other magnolia cultivars are grafted. Not suitable for very small gardens or positions where large, saturated-color flowers are expected.

How to Identify

Flowers are 3–4 inches (8–10 cm) across, white, with 6 tepals plus 3 smaller sepal-like outer tepals, lightly fragrant, on bare branches late March–April. Leaves are alternate, obovate, 3–6 inches (8–15 cm), medium to dark green. Crown is broadly pyramidal to rounded at 25–40 feet (7.5–12 m) tall. Seedlings take 10–15 years to reach flowering maturity. Compared with M. stellata, mature tree size is 15–20 feet (4.5–6 m) taller, flower tepal count is 6 plus 3 outer rather than 12–18, and flower form is cup-shaped rather than star-shaped; compared with M. denudata, flowers are 2–3 inches (5–8 cm) smaller and the crown is more rounded at maturity; compared with M. x kewensis 'Wada''s Memory', flowers are 2–3 inches (5–8 cm) smaller and new foliage is green rather than bronze-red.

Appearance

Size & Dimensions

Height25' - 40'

Width/Spread25' - 35'

Reaches mature size in approximately 20 years

Colors

Flower Colors

white

Foliage Colors

green

Fall Foliage Colors

yellow

Bloom Information

Bloom Period

~3 weeks

Spring

Flowers 3–4 inches (8–10 cm) across, white, with 6 tepals plus 3 smaller sepal-like outer tepals, lightly fragrant, on bare branches from late March through April over a 2–3 week window. Seedling trees reach flowering maturity at 10–15 years; grafted specimens flower at 3–5 years. Late frosts below 28°F (–2°C) damage open flowers.

Detailed Descriptions

Flower Description

White flowers 3-4 inches across with 6 tepals plus 3 smaller outer sepal-like tepals; lightly fragrant; on bare branches late March-April

Foliage Description

Medium to dark green; alternate, obovate, 3-6 inches long; emerging after flowers fade

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.0 - 7.0(Neutral)

357912

Soil Types

loam clay silt

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

10-15 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Grow in full sun to partial shade with 4–10 hours of direct light in moist, well-drained loam, clay, or silt at pH 5.0–7.0. The species tolerates a wider soil pH range than most magnolias, including soils up to pH 7.0, and accepts heavier clay soils with adequate drainage. Water deeply once per week during the first three growing seasons, then maintain moisture during extended drought. Apply 2–3 inches (5–8 cm) of organic mulch over the root zone in spring. The long juvenile period from seed (10–15 years) means seedling-grown specimens may not flower for more than a decade; grafted plants flower within 3–5 years. No significant pest or disease problems have been reported. Hardy to USDA zone 4, with sustained winter temperatures to –30°F (–34°C).

Pruning

Prune in late spring after flowering when needed. Develop a single central leader during the first 3–5 years if a single-trunk form is desired. The naturally pyramidal to rounded mature form requires minimal pruning beyond removal of dead, crossing, or damaged branches. Heavy pruning regrows slowly on magnolias.

Pruning Schedule

late spring