All too often people consider magnolias to be tender, southern plants. In reality, you can grow a number of magnolias in USDA zone four areas. In Minnesota, zone four means the southern third of the state, areas along Lake Superior and a strip of land along our border with North and South Dakota.
Fortunately, larger garden centers do carry some of these hardy magnolias. The following is a discussion of those types that you are most likely to see.
Star Magnolia, Magnolia kobus var. stellata is the major player in northern nurseries and gardens. It is beautiful all season long, but its early bloom helps signal spring's arrival. In late April or early May, its flower buds swell to reveal white, star-like blossoms with long petals. These fragrant flowers are six inches in diameter if spread flat. Leaves emerge with a bronze hue, changing to an attractive medium green throughout the rest of the growing season.
Star magnolia's habit is uniform and upright, but branches are spreading and somewhat tiered. Plants can grow to be ten feet tall or more, and almost as wide. Fall color can range from a good, butter yellow to a rust color. On occasion, the leaves may also fall off when they're still green. Once limbs are bare, you can already see flower buds for next season's bloom. These are an attractive silver-grey and offer interest throughout the winter.
'Leonard Messel' and 'Merrill' Magnolias
'Leonard Messel' and 'Merrill' magnolias result from crosses between the tree-like Magnolia kobus and its shrubby variety stellata. Both offer hardiness and the early blooming characteristic of the star magnolia, but they ultimately grow larger. They bloom alongside the star magnolia in mid-spring. Throughout the season, these plants offer the same great foliage and seasonal interests as star magnolia. Which plant to choose likely depends on available space and your preferred color scheme.
'Leonard Messel' offers lovely pink blossoms with white inner petals. There is just nothing else like it. Flower color can vary from a lighter to a darker shade depending on the season's temperatures, but most years, it is an outstanding flamingo pink. You can count on plants to grow fifteen feet tall and ten feet wide.
'Merrill' is a symmetrical, extremely vigorous and large growing white-flowered magnolia. There are a few older plants in the area that are two stories tall and fifteen feet wide. Pruned up to reveal its smooth grey trunk, this plant makes a choice alternative to crabapples.
Magnolia acuminata seed pod
Photo credit: Beth Jarvis
Cucumber Tree Magnolia
Cucumber Tree, Magnolia acuminata, is the final member of the genus worth noting for its reliability in this climate. The name, cucumber tree, refers to its fruit aggregates, which roughly resemble cucumbers. This magnolia is not grown for its flowers. Instead, people grow it for its value as a large, sturdy, and beautiful shade tree. There is an outstanding specimen in Lyndale Park of Minneapolis and two more on the East Side of Lexington Avenue near Lake Como.
When you see these beautiful plants, you'll wonder why this tree is not more commonly grown. The habit is not unlike that of a basswood (Tilia species); plants are symmetrical in youth and more open with maturity. These trees can ultimately grow to be eighty feet tall and forty feet wide.
*When planting any magnolia, start with a container grown plant. Magnolias do not tolerate the root disturbance associated with balling and burlapping or bare-rooting as readily as many other tree species.
*All magnolias will grow best in full sunlight. They will grow in light shade, but bloom will be more sparse and plant habit will be open and less symmetrical.
*Magnolias are adaptable to a variety of soil types, but adequate moisture is essential and you should avoid highly alkaline soils. Water during dry periods to keep your magnolia from wilting.
*Plant magnolias in protected locations out of the wind, if possible.
*Begin fertilizing as your magnolia is leafing out. A balanced fertilizer with equal parts nitrogen, phosphorous and potassium applied annually will help keep it healthy. Use a granular, slow release fertilizer that will nourish the plant as it grows throughout the season. The spring after planting is a good time to begin fertilizing.
*Fortunately, there are no major insect or disease problems with these plants.