Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
3/27/00
Yard and Garden Column for the Week Beginning March 31
Contacts:
Cindy Haynes, Horticulture Extension, (515) 294-4006,
chaynes@iastate.edu
Elaine Edwards, Extension Communication systems, (515)
294-5168, eedwards@iastate.edu
Magnolias for Iowa Gardens
By Cindy Haynes
Extension horticulturist
Iowa State University Extension
One of the most beautiful groups of flowering trees is the magnolia. The regal flowers of southern magnolia (Magnolia grandiflora) grace landscapes throughout the southeastern United States. They have even appeared on a postage stamp. However, this southern beauty is just that….southern. Southern magnolia will not tolerate Iowa's harsh winters. However, there are several other magnolia species with equally attractive flowers that perform well in Iowa. Their elegant flowers appear from early April through May.
Magnolias are a diverse group of plants with pink, purple, white and even yellow flowering types. Flowers on most are fragrant, varying slightly with species. Plant size can vary greatly as well. Many are medium to large trees with some reaching more than 50 feet tall. Others are considered large shrubs only reaching 8 to 12 feet tall. Because of their diversity, there is a magnolia for virtually every site in the landscape.
Cucumbertree magnolia (Magnolia acuminata) is native to the United States from Louisiana to New York. It is hardy to Minnesota. This tree is "large" in many respects. The leaves can be up to ten inches long and the tree often reaches 50 feet or more in height. However, the flowers are relatively small -- only 2 to 3 inches long and greenish yellow in color. While the flowers are quite attractive, they are not readily seen since they are often hidden by the foliage. Flowering begins in late spring and is rarely affected by frosts. The fruit, appearing in late summer, is worth searching for since it resembles a cucumber, hence the common name.
While the flowers on the cucumbertree magnolia often go unnoticed, the blooms of some of its offspring are quite showy. Because of their unusual greenish yellow flowers, the cucumbertree magnolia has been crossed with other magnolia species to develop yellow-flowering selections. 'Elizabeth' was the first yellow-flowering magnolia sold and is still one of the best available on the market today. Recently, several other yellow magnolias have been introduced. Competitors such as 'Butterflies,' 'Yellow Bird,' 'Yellow Fever,' 'Yellow Garland,' 'Sundance' and 'Miss Honeybee' reportedly offer more vibrant yellow flowers. Only time will tell if they can surpass the elegance of 'Elizabeth.' 'Elizabeth' will reach 30 feet tall with a 15 to 20 foot spread. Unlike the cucumbertree, the yellow magnolia hybrids flower before the leaves emerge fully in spring, making the show much more spectacular. Since the yellow-flowering hybrids bloom later than most magnolias, they are rarely damaged by frosts.
Another large magnolia with showy flowers is the saucer magnolia (Magnolia x soulangiana). Sometimes called the tulip tree, this magnolia puts on a spectacular show producing large, pinkish purple flowers in early spring. When this tree is in full bloom it can stop traffic. The flowers are lightly fragrant. Unfortunately, our fickle weather in early spring can be a problem. Freezing temperature can turn beautiful flowers into dead, brown masses. Give this species plenty of room, since saucer magnolia normally reaches 30 feet tall with a spread of 20 feet.
In locations where smaller trees are needed, the loebner magnolias (Magnolia x loebneri) are excellent choices. With heights from 15 to 25 feet, they are suitable for sites near the home. 'Merrill' is one of the hardiest of the loebner magnolias surviving beautifully at the Minnesota Landscape Arboretum (USDA Hardiness Zone 4a). The white flowers are smaller than the saucer magnolia but contain more petals (tepals, technically). They also flower a couple of weeks later than the star and saucer magnolias, oftentimes escaping injury from late frosts. 'Leonard Messel,' another lobener magnolia cultivar, is noted for its pale pink flowers.
Coming down in size once again is the star magnolia (Magnolia stellata). Star magnolia is the first magnolia to bloom. As a result, the flowers are occasionally zapped by late spring frosts. Don't cross the star magnolia off your list because its white flowers are occasionally destroyed. In 3 or 4 years out of 5, it's fantastic! Flowers are smaller than those of saucer magnolia but the petal count is much greater. Mature heights range from 12 to 20 feet with spreads around 12 feet. It is also one of the hardiest magnolias.
For plants with smaller statures but equally impressive floral displays there is the Little Girl series of magnolias. This series of hybrids was developed at the National Arboretum in the 1950s for shrub-like form and colorful flowers. Each of eight different cultivars, aptly named 'Jane,' 'Judy,' 'Betty,' 'Ann,' 'Ricki,' 'Susan,' 'Randy' and 'Pinkie,' are large shrubs ranging in height from 8 to 15 feet. Flowers vary slightly between cultivars but are generally challis-shaped and usually pink or purple in color. Flowers appear later in the spring season thus avoiding destruction by late spring frosts. Flowers usually appear just prior to or with the emerging leaves. The habit varies slightly between cultivars with 'Ricki' being rather upright and 'Betty' more spreading or rounded.
Planting and Maintenance
Magnolias prefer a full sun location with well-drained soils. They are adaptable to soil types, even tolerating clay soils, but they insist on good drainage. Waterlogged soils often lead to an early demise. Spring planting of larger specimens is best as most root growth occurs in spring.
Magnolias are relatively pest and disease free. On occasion, magnolia scale or mildew will attack a tree. These problems only warrant treatment in severe cases as they tend to be cyclic in nature. Contact your county extension office for treatment options if problems arise. As one magnolia aficionado once said, "Their biggest problem is not pests, it is that they don't flower long enough."
Magnolias are considered one of the oldest families of flowering plants. They have survived on earth for thousands of years. Thankfully they are still around to add a little elegance to our landscape every spring.
ml: isugarden
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