Magnolias for Minnesota
Steve Poppe, Sr. Horticulture Scientist
All too often people consider magnolias to be tender, southern plants. In reality, you can grow a number of magnolias in USDA Hardiness Zone 4b. In the Morris area, we are on the northern edge of Zone 4b. Larger garden centers may carry some of these hardy magnolias. The following are the types 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 gold, 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.
Centennial Blush Star Magnolia
Pink buds open to incredibly full and wonderfully fragrant pale pink flowers in spring on this beautiful magnolia. Centennial Blush is a prolific bloomer with flower buds formed at almost every node yielding a fantastic floral display of delicate pink covering the entire plant. Attractive medium green foliage on an interesting branching structure follows in the summer turning yellow to bronze in autumn. Centennial Blush can be grown as a large shrub or a small tree, perfectly suited for small urban gardens.
Flower buds are tapered and open to primrose-yellow blooms which appear before leaves. At maturity, the flower measures up to 3" across. Deciduous tree with a pyramidal habit, rather upright.
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.