Magnolias might seem like a hallmark tree of the south, but that doesn't mean people in Des Moines, Iowa, and Portland, Maine, can't enjoy them too. There are several species of magnolia that are cold-hardy enough to endure minimal temperatures that average between 10 to -20 degrees Fahrenheit, which is what makes an area fall into zone 5.
Gardeners looking for a fast-growing shade tree can't go wrong with the cucumbertree magnolia (Magnolia acumiate). It grows between 60 to 80 feet tall with a 40-foot spread. It produces greenish-yellow flowers about 4 inches wide in May to early June. Flowers turn into a pinkish-red fruit that resembles a cucumber, which is how the tree gets its name. It can withstand flooding and has a moderate tolerance to drought. Soil should be moist, well-draining in sun to partial shade.
One of the most striking features of the umbrella magnolia (Magnolia tripetala) is its 6- to 8-inch white flowers that bloom in May or June. Unfortunately, the flowers tend to have an unpleasant odor. It grows about 15 to 40 feet tall. Plant it in a moist, well-draining soil in partial shade or full sun.
The Japan-native Korbus magnolia (Magnolia kobus) is a slow-growing tree that typically reaches a height of 25 feet or less in the U.S. Although it does not flower well when it is young, with maturity comes showy white flowers about 3 to 4 inches wide with a light, pleasant fragrance. This is one of the first magnolias to flower in the spring. Plant Korbus magnolias in a well-draining soil in either part-shade or full-sun location. It tolerates a wide range of soil types.
The star magnolia (Magnolia stella) is a variety that requires a little pruning to develop a strong, tree-like structure. If not pruned, it tends to resemble a large shrub. It is a hardy magnolia that can withstand some flooding and has a moderate drought tolerance. It produces fragrant, 3- to 4-inch-wide white flowers in the spring. It will grow about 20 feet high and 15 feet wide. For best results, plant it in a rich, slightly acidic soil in full sun.
The sweetbay magnolia (Magnolia virginiana), or swamp magnolia, has 2- to 3-inch-long white flowers with a lemon scent. Flowers are visible, but not showy, in the late spring and early summer and turn into a bright red fruit that is attractive to birds. Its dark green leaves have a silver underside. It should be planted in moist, acidic soil in full sun to partial shade. It grows about 20 to 40 feet tall with a 20-foot width.
The saucer magnolia (Magnolia x soulangeana) is a hybrid that grows about 20 feet tall with a similar spread. It produces large pinkish purple flowers between late February and early April. Flowers can reoccur over the summer. It is fast-growing and has a good pollution tolerance. Plant it in full sun in a moist, deep, acidic soil.