Hickory Tree Species

True Hickories

• If you are a nut-lover, you have heard of hickories and pecans. Both are Carya species. The subgenus Carya includes the true hickories, such as Carya glabra, C. laciniosa, C. ovata, C. pallida and C. tomentosa, called pignut, shellbark, shagbark, sand and mockernut hickories, respectively. With the exception of the pignut, all these hickories have sweet-tasting nuts, although the shellbark's nuts are larger and may be the best tasting.

  For ornamental use, the shagbark provides year-round interest with its distinctive and attractive bark. All can serve as large shade trees if you have room for them in your landscape.

Pecan Hickories

• The subgenus Apocarya, includes the pecan hickories, such as Carya aquatica, C. cordiformis, C. illinoenensis and C palmeri, or the water hickory, bitternut hickory, pecan and Mexican hickory, respectively. The familiar pecan is quite delicious, while the water, bitternut and Mexican hickories are not. The bitternut hickory may be the most common native hickory. It thrives under both wet and dry growing conditions, and is a medium size tree, so it has value as an ornamental shade tree, like the true hickories.

Asian Hickories

• Some Carya species are Asian natives, all but one of which are in the subgenus Sinocarya. Rarely grown in the United States, these Asian hickory natives include Chinese hickory, C. cathayensis and the Vietnam hickory, C. tonkinensis. Another Asian native, the beaked hickory has its own category, Annamocarya sinensis.

Warning

• Hickory trees have many desirable qualities in the landscape, but Carya are members of the Juglandaceae family, which includes the black walnut, Juglans nigra, known for its production of juglone. This toxin can make it hard to grow other plants nearby, although hickories do produce less juglone than black walnuts.

  In addition to their potential toxicity to nearby plants, every Carya species native to the United States produces pollen each spring that is labeled by Pollen.com as a severe allergen. Therefore, think twice about planting hickory tree species where they might cause problems for you, your other garden plants or both.