Several species of ornamental magnolias grace the Missouri landscape with colorful flowers from March through mid-June. With their prolific bloom, magnolias' sweet, citrusy floral fragrance permeates the air and beguiles the senses when planted in the landscape. Flower color ranges from pink, purple, white, yellow, and green depending on the species and cultivar.
In addition to being a delight to the senses, magnolia flowers have a fascinating history. The showy, fragrant magnolia flowers evolved millions of years ago during the Cretaceous period to attract flightless beetles for pollination before other common insects, such as bees, butterflies, and moths were in existence.
Magnolias also developed specialized plant parts to withstand some types of insect damage. On southern magnolia (Magnolia grandiflora), the large tree leaves are leathery. The flowers of magnolia species consist of thick, petal-like structures, called tepals. Because beetles are chewing insects that feed on plant parts as they harvest the pollen, magnolias also developed thick carpels (a floral structure that bears ovules) for protection against feeding damage. These tough carpels also prolong the time that beetles spend on the flower parts, ensuring pollination.
Many of the magnolias in Missouri landscapes are deciduous and grown as large shrubs, or pruned to a single trunk to develop a small tree, except for the southern magnolia. Most species will tolerate clay soil and are best grown in full sun to part shade. Due to their early spring bloom, deciduous magnolias can be damaged by freezing temperatures. To delay bloom and enhance the likelihood of flowering, avoid sites with southern exposure. If needed, deciduous magnolias are pruned after flowering. Water magnolia shrubs and trees during periods of drought. Serious insect pests and diseases on magnolias are uncommon.
The first species to bloom in Missouri is the star magnolia (Magnolia stellata). It is usually grown as a large shrub, reaching 15 to 20 feet tall at maturity. Star magnolias have fragrant flowers with white, strap-like tepals that appear in March to early April. To prolong the bloom period and minimize tepal browning, plant star magnolias in a site that is protected from high winds.
Lobner magnolia (Magnolia × loebneri) is a hybrid that grows to 10 to 20 feet tall at maturity. Cultivars of this hybrid develop perfumy flowers with 10-15 tepals that vary in color from white, blush pink to purplish-pink. The bloom period in central Missouri is usually mid-March.
The Little Girl series, which was developed at the National Arboretum, are hybrids of Magnolia liliiflora × M. stellata. These slow-growing, deciduous plants reach 20 to 25 feet tall at maturity. The cultivars, 'Ann', 'Betty', 'Jane', and 'Judy' have flowers with light to dark pink tepals. These cultivars generally bloom one to two weeks later than star magnolia cultivars and are less likely to be nipped by spring frosts.
Butterflies magnolia is a cultivar of the deciduous hybrid (M. acuminata × M. denudata). When trained to a pyramidal tree form, it can reach 18 to 20 feet tall at maturity. A showy display of bright yellow flowers usually appears about one to two weeks later than most star magnolia blossoms. Another cultivar resulting from a M. acuminata × M. denudata cross is Ivory Chalice. However, this cultivar develops large (6 inch-diameter) creamy-white flowers that bloom about 2 weeks later than Butterflies magnolia flowers in central Missouri.
Saucer magnolia (Magnolia × soulangeana) is a widely-grown species that bloom a bit later and grows taller (20 to 25 feet) than star magnolia. There are several cultivars of saucer magnolia with cup-shaped flowers ranging in color from white, pink, magenta, and burgundy. The first bloom is the most spectacular. After this, a few flowers continue to appear on the new growth but tend to be less striking.
The cucumber tree (Magnolia acuminata) is the only magnolia native to Missouri and is found growing in southeastern counties near the Mississippi River. It is a large deciduous tree species that typically grows to 40 to 70 feet tall, but can reach 100 feet tall. The greenish-white tepals of its flowers are considered less spectacular than other magnolias. Thus, this tree species may be better known for its green, cucumber-shaped, cone-like fruit that develops after flowering and its foliage that turns a gold color in the fall.
Southern magnolia (Magnolia grandiflora) is a large, broadleaf evergreen tree species native to the southeastern United States. Leaves are dark glossy green on the top side and a brownish color on the underside. Fragrant white flowers begin to appear in central Missouri from May to June. Following bloom, cone-like fruit develop on trees with beautiful, red-colored seeds. Southern magnolia trees often suffer from winter injury when grown in Missouri, displaying symptoms of foliar browning. However, the cultivar, 'Bracken's Brown Beauty' is more reliably cold hardy in central and southern regions of the state. The dense, fuzzy hairs on the underside of its foliage retard moisture loss which results in leaf discoloration during the winter months.