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Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915

4/12/99

Contacts:
Cindy Haynes, Department of Horticulture, (515) 294-2751
Elaine Edwards, Extension Communication Systems, (515) 294-5168

Yard and Garden Column for the Week Beginning April 16

Spectacular Spring Flowering Shrubs

By Cindy Haynes
Extension horticulturist
Iowa State University Extension

Gardeners can select from several wonderful spring flowering shrubs. These plants light up the landscape from early spring to early summer with their colorful blossoms. After blooming, these plants often fade into the background, allowing the summer flowering plants to take center stage.

One of the first shrubs to herald the arrival of spring is forsythia (Forsythia hybrids). Their bright yellow blooms brighten the landscape for a couple of weeks in early spring. Plants prefer full sun to light shade and a well-drained soil. Plant size ranges from 3 to 8 feet. Flower buds on many older forsythia varieties often are destroyed during Iowa winters. This is apparent in spring when only the lower half (below the snow line) of the shrub blooms. There are several hardy cultivars from the Midwest that bloom reliably each spring. 'Sunrise' is a 5-to 6-foot-tall, Iowa State University introduction with bright yellow flowers. 'Northern Sun' is an 8- to 10-foot-tall introduction from Minnesota with clear yellow flowers in spring. An introduction from North and South Dakota is 'Meadowlark,' which has bright yellow flowers on 6- to 9-foot-tall shrubs.

For an easy-to-grow shrub or small tree that is extremely cold hardy, consider one of the many peashrubs (Caragana sp.). These durable shrubs or small trees tolerate a wide range of soils, drought, alkalinity, salt and high winds. They have bright, yellow pea-like flowers in mid to late spring. Size ranges from 3 to 15 feet tall depending on species and cultivars. Siberian peashrub (Caragana abrorescens) is a small tree while Russian peashrub (Caragana frutex) is more shrub-like. Peashrubs prefer full sun for best flowering but will tolerate partial shade as well.

For a small shrub in shade, fothergilla (Fothergilla gardenii) is an excellent choice. This 2- to 5-foot-tall shrub has creamy-white, bottle brush-like flowers in early spring. The flowers appear before the leaves and often possess a honey-like scent. In summer, leaves are a dark green or bluish green changing to brilliant yellow, orange or scarlet in fall. Fothergillas prefer partial shade with a moist, well-drained, acid soil.

Azaleas and rhododendrons are popular spring flowering shrubs. There are thousands of cultivars available but, unfortunately, most are not hardy in the upper Midwest. Some of the best azaleas for Iowa gardens are from the Light Series introduced from the Minnesota Landscape Arboretum. These azaleas offer pink, white, yellow, orange, lilac or bi-color blooms that are often fragrant, and range from 6 to 10 feet in height. These azaleas bloom before the leaves emerge in spring, making the flowers even more brilliant. However, these azaleas will lose their leaves in the fall. For an evergreen rhododendron, the best options for Iowa gardens are 'PJM' or 'Olga.' These 3- to 6-foot tall shrubs are one of the first rhododendrons to bloom in the spring. 'PJM' has vivid lavender-pink blooms while 'Olga' has bright peach-pink blooms. The leaves often change from a dark green in the summer to reddish or burgundy in fall and are retained throughout the winter. Azaleas and rhododendrons are best suited for partially shaded sites with acid, well-drained soils. Protection from winter winds also is beneficial.

Vanhoutte spirea (Spirea vanhouttei), sometimes referred to as bridal wreath spirea, is another sign of spring. This 4- to 8-foot-tall shrub is literally blanketed in tiny, pure-white flowers on arching, fountain-like stems in mid-spring. The blooms last for only a couple of weeks in spring but are usually worth it. This spirea performs well in full sun to partial shade with a well-drained soil. There are many other durable spirea species that offer pink or white flowers later in summer.

The queen of all spring-blooming shrubs has to be the lilac (Syringa vulgaris hybrids). These popular shrubs offer fragrant blossoms in a wide variety of colors (pink, white, lilac, purple, blue and bi-colors) and single or double flowers. 'Sensation' is a cultivar noted for its spectacular dark purple florets edged in white. Lilacs range in height from 6 to 15 feet depending on cultivar. They prefer full sun and do not flower well in shady locations. Avoid planting lilacs in partial shade as several cultivars are susceptible to powdery mildew. Where smaller plants are desired, 'Dwarf Korean' (Syringa meyeri) or 'Miss Kim' (Syringa patula) may be suitable. Both grow approximately 6-feet tall and bloom later than most lilacs.

Several species of viburnum produce attractive, fragrant blooms in early spring. Flower buds are pink opening to white and often appear prior to the emergence of the foliage. Plant heights range from 5 feet for Koreanspice viburnum (Viburnum carlesii) up to 8 feet for burkwood viburnum (Viburnum burkwoodii). The lustrous, dark green leaves are attractive all season. Fruit that starts out red and changes to black can be showy in late summer. Plants prefer partial shade with moist, fertile, well-drained soils.

Old fashioned weigela (Weigela florida) is another one-season shrub wonder in the garden. This 6- to 9-foot-tall shrub has showy, trumpet-shaped blooms that cover the plants in late spring. Flower color variety includes white, yellow, red and pink shades. 'White Knight' is a 5- to 6-foot-tall shrub introduced from ISU with lovely white flowers. 'Minuet' is a dwarf variety with reddish-pink flowers on 2- to 3-foot-tall plants. Several variegated leaf cultivars offer summer interest in addition to their flowers with green and yellow or creamy white leaves.

For larger shrubs or small trees with spring bloom, serviceberry, fringetree or star magnolia offers beauty to the landscape. These plants can reach 15 to 20 feet tall with 10 to 15 foot spreads. Serviceberry (Amelanchier sp.) has white flowers in early spring followed by edible, blueberry-like fruit in summer. Serviceberry leaves turn shades of yellow, orange and red in fall. Plant in full sun to part shade for best blooms. Fringetree (Chionanthus virginicus) is a slow growing large shrub with white strap-like hanging, flowers in mid to late spring. This relative of ash does best in partial shade with moist, fertile, well-drained soil. The lustrous green leaves turn an attractive clear yellow in fall. Star magnolia (Magnolia stellata) has white or pale pink flowers in early spring. Late spring frosts often damage or destroy the flowers on this early blooming plant. However, when the weather is favorable, the blossoms are first rate. Plant star magnolia in full sun in a well-drained soil.

Care of Spring Blooming Shrubs

These shrubs are durable and require minimal care if placed and planted properly. Since these shrubs bloom on the previous season's wood, they should be pruned immediately after flowering. Late winter or early spring pruning will reduce flower numbers in spring. Fertilization is unnecessary for many of the spring flowering shrubs. In fact, if they are fertilized too heavily they may not flower well at all.

Some other options in spring-flowering shrubs include flowering almond (Prunus glandulosa), flowering quince (Chaenomeles speciosa), slender deutzia (Deutzia gracilis), daphne (Daphne hybrids), mockorange (Philadelphus coronarius) and beautybush (Kolkwitzia amabilis).

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