The forsythias were spectacular this spring in Iowa. Many of the shrubs were completely covered with bright, yellow flowers. Unfortunately, this is not always the case. Many of the forsythia varieties that have been widely planted in past years, such as 'Lynwood Gold' and 'Spring Glory', don't reliably bloom in Iowa. (They usually bloom well once every 4 to 5 years.) Their flower buds are killed by low winter temperatures. These varieties bloomed well this spring because of the relatively mild winter. Home gardeners wishing to plant forsythia should choose varieties that possess excellent flower bud hardiness. These hardy varieties should bloom reliably in Iowa each spring.
An excellent forsythia for Iowa is 'Sunrise'. 'Sunrise' is an Iowa State University introduction that has bloomed well after temperatures of -20oF. It is a semispreading, compact shrub with a mature height of 5 feet and a similar spread. The leaves are medium green. In cool, dry fall weather the leaves may develop a purplish cast. Young stems have 4 longitudinal ridges which give them the appearance of being square. While the bright yellow flowers are relatively small, the large number of blossoms per branch results in a mass of color. The compact habit of 'Sunrise' makes it ideal for small hedges or specimen plants.
Another hardy forsythia is 'Meadowlark'. Jointly introduced by North Dakota State and South Dakota State Universities, in collaboration with the Arnold Arboretum, 'Meadowlark' has consistently bloomed in both states. Flower buds have successfully survived temperatures of -35oF. Flowers are a bright yellow. A vigorous, rapidly growing shrub, it reaches 6 1/2 to 9 feet in height. 'Meadowlark' has dark green leaves. Under favorable conditions, the leaves often change to a golden yellow in the fall.
'Northern Sun' is an introduction of the University of Minnesota. Grown at the Minnesota Landscape Arboretum in Chanhassen, 'Northern Sun' has bloomed when temperatures dropped to -30oF. The clear yellow flowers cover the plant in early spring. Foliage is a medium green. The vigorous shrub reaches a height and spread of 8 to 10 feet. Because of its large size, 'Northern Sun' is best suited for a tall hedge or screen. Other hardy forsythia varieties include 'Northern Gold', 'New Hampshire Gold', and 'Vermont Gold'.
These hardy varieties are available at many local garden centers and mailorder companies.
This article originally appeared in the May 5, 1993 issue, p. 61.