Fall color is beginning to paint tree canopies around central Illinois, making the next few weeks prime time for taking in the beauty. Among our native trees, sweet gum (Liquidambar styraciflua), red maple (Acer rubrum) and sugar maple (Acer saccharum) typically get credit for the most beautiful and colorful display, but many of Illinois’ native oak trees put on a wonderful show of their own.
Shorter days and colder nights have started to set the autumn colors in motion, with many sweet gums and sugar maples in rural areas beginning to develop color over the past week. Many of the oaks hold out a little longer, although I have notice some fall color on white oaks (Quercus alba) outside of the more protected city streets and yards.
White oak is somewhat common as an urban tree or street tree throughout Illinois, developing a large, spreading canopy over time and maturing into an excellent shade tree with outstanding structural stability due to great rot-resistance in the trunk and limbs. In my yard, it is usually one of the first oaks to begin to show fall color, developing its best color early in the season. The relatively large and multi-lobed leaves begin with an often brilliant reddish color that fades into variable shades of brown as the fall season progresses.
Many may not be aware that the white oak is actually our state tree in Illinois, earning it special significance along with our more commonly known state bird, the cardinal, and state insect, the monarch butterfly. It is a common forest species statewide, typically occupying a large percentage of the overstory in upland forest stands.
Botanically speaking, all oaks belong to the beech family (Fagaceae) although white oak, along with 6 other native oak species, make up a group frequently referred to as the “White Oak Family”. A more correct characterization would probably be “subgenus” as opposed to “family”, since all oaks are members of the same genus (Quercus), but we make a special division into a white oak group and a red oak group. The primary distinction between the two groups lies in their leaves, with the white oak subgenus having rounded lobes and the red oak subgenus adorning pointed tips on leaf lobes.
Perhaps the best color display among the white oak group is achieved by swamp white oak (Quercus bicolor). It has somewhat larger leaves than white oak, turning a variety of shades from yellow to brilliant, reddish purple. Look for swamp white oak’s peak color to develop a little later in autumn than white oak.
Another favorite in the landscape among the white oak subgenus is the bur oak (Quercus macrocarpa) due to its tough resilience and adaptability to a wide variety of urban environments. It is perhaps my favorite, most recommended oak to plant as I have had the greatest success with it over the years. Although fall color on bur oak is often a less vibrant yellow to brown, it’s unique corky twigs provide excellent winter interest later in the year.
The red oak subgenus, making up the balance of our 21 native oak species, has quite a few members that offer great fall color. Northern red oak (Quercus rubra) turns a wonderful red to reddish-brown color that fades to various shades of brown over the fall season. Pin oak (Quercus palustris), which may be the most planted oak in urban areas, also has an excellent red fall color across its more slender and sharply pointed leaves. Shingle oak (Quercus imbricaria) is quiet similar to pin oak in many aspects although its un-lobed leaves certainly distinguish it from other members of the red oak group. It does develop a pretty red-brown to yellow-brown fall color that fades to a variety of brownish colors on leaves which commonly persist into winter, adding a bit of winter interest and shelter for wildlife.
Two other members of the red oak group are less common in the urban setting, but also boast great fall color. Black oak (Quercus velutina), named for its black-colored and deeply furrowed bark, hosts an attractive fall display of yellow brown to almost reddish-brown foliage. Shumard oak (Quercus shumardii) is probably an under planted urban tree as it does well in a wide range of soils from dry conditions to wet spots. It displays nice reddish-brown foliage as fall ensues, saving its color for later in the season.
Don’t pass up the opportunity to take in the fall palette of color among all of our native trees over the next few weeks. Moderate temperatures on sunny days will provide some of the best Illinois weather of the year, making it a great time to visit central Illinois parks and natural areas in seek of autumn beauty.