Magnolia acuminata
The only magnolia species native to Canada and the cold-hardiest of all magnolias. A large deciduous forest tree producing small yellow-green flowers, cucumber-shaped fruit, and striking red seeds. Listed as Endangered in Ontario and protected under the federal Species at Risk Act.
Bloom & Fruit
Small, yellow-green, tulip-like flowers 5-8 cm across with 6-9 upright tepals. Borne high in the crown and often overlooked. Flowers are not showy compared to most magnolias but are subtly fragrant. Blooms in late spring as leaves emerge.
Growing Conditions
Garden Uses
- RareUncommon in Ontario. Sourcing should prioritize nursery-propagated stock over wild collection.
- Bird FoodSeeds, berries, or nectar feed songbirds. Leave seedheads standing over winter for goldfinches and sparrows.
- EdibleParts of this plant are edible. Research proper identification and preparation before consuming.
Where to Buy
Ecology
Native Habitats
Associated Fauna
Propagation
- Seed (cold-moist stratification 3-6 months)
Details
Description
Magnolia acuminata is the only magnolia species native to Canada and the cold-hardiest member of its genus. It is a large, deciduous, round-topped forest tree typically reaching 15-20 metres in cultivation but capable of exceeding 30 metres in ideal forest conditions. The United States national champion in Stark County, Ohio, measures nearly 2.4 metres in diameter and 29 metres tall. The tree tends to occur singly as scattered specimens rather than in groves.
The leaves are simple, alternate, oval to oblong, 12-25 cm long and 6-12 cm wide, with smooth entire margins and a downy underside. They are deep green in summer and turn yellow-brown in autumn. The specific epithet acuminata refers to the leaves tapering to a fine point at the tip. The bark is grey-brown with narrow, shallow furrows and scaly ridges on older trunks.
The common name "cucumber tree" derives from the distinctive fruit: an aggregate of follicles forming a green, cucumber-shaped cone 6-8 cm long that matures to dark red in late summer. As the carpels split open, they reveal 10-60 bright red seeds suspended on fine threads — one of the most ornamental fruiting displays among native trees. The flowers, by contrast, are unusually modest for a magnolia: small, yellow-green, tulip-like blooms 5-8 cm across, borne high in the crown where they are often overlooked.
Growing Conditions
Thrives in deep, rich, moist, well-drained, acidic soils. Naturally found on wooded slopes, stream banks, and rich upland forests of the Carolinian zone. Prefers full sun but tolerates part shade. Requires consistent moisture; does not withstand extreme drought or prolonged wetness. While preferring acidic conditions (pH below 6.8), it shows some tolerance of alkaline soils.
Hardy from USDA Zone 4 through Zone 8. In Ontario, it is restricted to the warmest regions of the Carolinian zone, where it reaches the northern limit of its range. Sensitive to pollution and not recommended for urban street plantings. Few diseases or pests affect it, though mature trees are reluctant to heal wounds or pruning cuts. Transplanting is challenging due to the coarse, fleshy root system; specimens should be moved in early spring with a generous soil ball.
Phenology
Flowers appear from May through June, borne high in the crown as the leaves emerge. The yellow-green blooms are pollinated primarily by beetles, reflecting the ancient evolutionary lineage of the Magnoliaceae. The cucumber-like fruit develops through summer, maturing from green to dark reddish-orange by August through October. Individual carpels split open to reveal the bright red seeds, which remain attached by fine silken threads before dropping. Autumn foliage colour is yellow-brown. The tree is fully deciduous, dropping its large leaves through late autumn.
Ecology
The flowers attract beetles and bees as pollinators, reflecting magnolias' ancient co-evolution with beetle pollination. The tree also serves as a larval host plant for butterflies, including the Eastern Tiger Swallowtail (Papilio glaucus), whose caterpillars feed on the foliage.
The fruit is highly attractive to wildlife. Seeds are consumed by ground-feeding birds including towhees and other sparrows, as well as small mammals such as squirrels and chipmunks. The large leaves contribute significant organic matter to the forest floor. As a Carolinian forest component, the cucumber tree is part of Canada's most biodiverse terrestrial ecosystem, though its scattered distribution means it does not dominate stands.
Propagation
Seeds require 3-6 months of cold-moist stratification at 1-5 °C. Collect fruit as the carpels begin to split in late summer, remove the fleshy red seed coat (aril) promptly, and stratify immediately. The fleshy aril contains germination inhibitors and should be removed by soaking and gentle abrasion. Sow stratified seed in spring in a protected nursery bed.
Growth is medium-paced. Young trees benefit from consistent moisture and protection from harsh sun. First flowering may take 10-15 years from seed. Vegetative propagation is difficult; grafting onto seedling rootstock is the standard method for cultivating select forms and hybrids. The species has been widely used in magnolia breeding programs to confer yellow flower colour and cold hardiness to ornamental hybrids.