The Buzz

Quercus Quirks #1: Red Oaks and White Oaks

By Linnea West, TUFC


Tennessee is rich in oaks with 20 distinct native species, divided by foresters and the lumber industry into red oaks and white oaks. How can we tell them apart?

Close observation of a few key features will allow you to discover secrets of internal structure, wildlife and landscape benefits, and preferred lumber use.

Beginning at the tips of branches, we look first at the leaves…
White oaks generally have rounded lobes with V shaped sinuses between them.

                                                             

Red oak leaves have pointed tips, usually with a bristle at the end and rounded sinuses.

                                                             

The acorns, too, have key distinguishing features…
On white oaks, acorns mature in one year, the nut meat is mild tasting, and the inner cup and shell are smooth.
Red oak acorns take two growing seasons to mature (trees will have two sizes of acorns at the same time – the smaller, younger ones on the outer, new-season growth). Red oak nut meats are more bitter-tasting due to the high tannin content and commonly have tiny hairs inside cup and shell. Both acorns are valuable for wildlife and provide important protein, fats, and carbohydrates, complementing each other even in lean years.

Looking at the bark, we see…
White oaks are a light or medium gray and appear scaly when mature.
Red oak bark is darker gray, sometimes nearly black, with furrows running the length and cross-ridges of various depth and spacing depending on the species.

If we could peer inside these magnificent oak trunks, we would see that the red oak group has redder heartwood than the white, but also, in cross-section, very open pores throughout its growth rings. White oak pores are plugged with tyloses creating resistance to decay and rot. This is why white oak species can be used for building boats and outdoor furniture, while red oaks are appropriate for interior furniture and cabinets.

On our Botanic Garden grounds we have 15 labeled oak species. Pick up a Tree Map at the Visitors Center and using these clues, have fun determining which are red oaks and which are white.

                                                                                 

Sources: Native Trees of the Southeast, Kirkman, Brown, Leopold 2007; Field Guide to Native Oak Species of Eastern North America, Stein, Binion, Acciavatti 2003; Identifying Oak Trees Native to Tennessee UT Extension PB 1731, Merker, Buckley, Ostby; Peterson Field Guides Eastern Trees, Petrides, Wehr 1988; Forest Trees of the United States and Canada and How to Identify Them, Little 1979; Fruit Key and Twig Key to Trees & Shrubs, Harlow 1946

Posted by Memphis Botanic Garden at 10:30 AM

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