The autumn colors were extraordinary this year, but why?
Weather conditions are the major factor in the development of fall color. The best fall colors are brought on by dry late summer and early fall conditions combined with warm sunny days and cool (not frosty) nights. Many think that frosty weather is a factor, but freezing temperatures too early in the fall can kill the leaves before they have the chance to turn color.
While weather is important in making New England a popular destination for fall “leaf peeping,” another essential element is the types of trees in their native hardwood forests. More than half of its tree population are sugar and red maples. These provide a huge part of New England’s autumnal show, but other trees, such as oak, beech, dogwood, and larch, also contribute to it.
If you are considering planting a tree with reliable fall color — such as red maple and its hybrids, red oak, scarlet oak, dogwood, or sweetgum — check the mature size of the tree. Some of these trees, such as scarlet oak (Quercus coccinea) with a mature height of 60 to 80 feet, grow into large shade trees that are not suitable for the average home lot. Look for cultivars that stay relatively “small” — only 35 to 40 feet tall — such as the red maples ‘October Glory’ and ‘Autumn Flame.’
As I ventured out last month to take photographs of beautifully colored trees, I also came across some shrubs that took my breath away. One of these was the oakleaf hydrangea (Hydrangea quercifolia), a shrub that I never really thought of as noteworthy before. Its flowers are pretty but not exceptional when compared to many other hydrangeas. However, in fall the oakleaf hydrangea is undeniably gorgeous with its leathery oak-shaped leaves turning rich burgundy-purple, red, orange-bronze, and yellow.
Another shrub with brilliant fall color is sweetspire (Itea virginica). I have ‘Little Henry’ in my landscape. This dwarf sweetspire cultivar grows only 2 to 3 feet tall. It has shiny green leaves that turn bright red and orange in fall. ‘Little Henry’ lights up the corner of the bed where it is planted. It is supposed to have a compact mounded habit, but my plant develops runners, sending up sprouts nearby. Nonetheless, it fits in well with ornamental grasses or in a woodland garden.
Yet another remarkable shrub is Korean spice viburnum (Viburnum carlesii). It is typically planted in home landscapes near the front door because of the sweet fragrance its flower clusters produce in mid-spring. However, in fall its leathery leaves turn red, burgundy and bronze. The species of this shrub can reach a height of 8 to 10 feet, a bit too big for most home landscapes. A better fit is a cultivar like ‘Spice Baby’ that only grows to 5 feet, or ‘Compactum’ that grows to 4 feet.
Other shrubs showing their magnificent colors this fall included witch hazel (Hamamelis x intermedia), Tiger Eyes cutleaf sumac (Rhus typhina ‘Bailtiger’), highbush blueberry (vaccinum corymbosum), heavenly bamboo (Nandina domestica), ninebark (Physocarpus opulifolius) and the renowned compact burning bush (Euonymus alatus ‘Compactus’).
What a glorious display of fall color nature provided us with this year!
Marianne C. Ophardt is a retired horticulturist for Washington State University Benton County Extension.