1 - Seedling trees may be difficult to identify, but not impossible.

Yard and Garden November 16, 2013

Q.

How can I distinguish Chinese Pistache from Tree of Heaven in a small seedling (less than six inches high)? I have a seedling that has come up in my yard. It has magnificent fall foliage, but I wonder if it is tree of Heaven that I do not want to allow to become established in my yard. A neighbor a few lots away has a small Chinese pistache tree, but there is also a lot of trees of Heaven around. The leaflets come in opposite pairs and vary from four to eight pairs with a terminal leaflet. One site indicated that Chinese pistache usually does not have a terminal leaflet. Otherwise, in a tree this small it seems likely that the leaves would be similar. Do Chinese pistache tree produce viable seed in the NE heights of Albuquerque? Thanks for your help.

Dan B.

A.

This is a challenging question. I also like to see what develops from a seedling that develops in my landscape and determine if it is a desirable or undesirable plant. A photograph would help, but I will provide information that may help you determine what tree you have. Chinese pistache trees do indeed have even pinnately compound leaves. They are prized for their excellent fall color and ability to grow in difficult environments. They are one of the best trees for red fall color in warm climates and tolerate dry conditions. It is possible for a seedling to develop from seeds dispersed from nearby trees. The problem is that the leaves on your seedling are odd pinnately compound (having a terminal leaflet). The tree of Heaven is another common tree with compound leaves. It rarely develops good fall color. When it does develop color, it turns yellowish before the leaves fall. The leaves of this tree tend to have more leaflets than those of the Chinese pistache. Some of the leaflets may have a wing or slight lobe at the base of the leaflet. Another characteristic of the tree of Heaven is its odor when the leaves are crushed or the stems are broken. Most people consider the odor of the tree unpleasant, some describe the odor of crushed leaves as resembling the odor of peanut butter. The lobes on some leaflets, the number of leaflets, and the odor may help you decide if this is the undesirable tree of Heaven that is hard to eliminate once established. Complicating this identification even more is the fact that there may be other possible trees to consider. A common tree with excellent purple fall color is the Raywood ash tree. This tree is considered seedless, but exceptions are possible and it may rarely make viable seeds. Another common ash tree with red or purple fall color is the white ash. It can make seeds and could be a candidate for your tree. Both of these have odd pinnately compound leaves with a terminal leaflet and great fall color. These ash trees have leaves arranged in an opposite manner on the stem (this is leaf arrangement, not leaflet arrangement). This differs from the alternate arrangement of leaves in the tree of Heaven and the Chinese pistache. A final consideration is that in many trees there is a juvenility phase in the seedlings. In some trees (and other plants), young seedlings may have characteristics that differ from those of the adult phase (mature) tree. Since this tree is a young seedling, you may want to wait until next year to make a final determination as to whether to keep it (final identification). If it is a tree of Heaven, you can remove it next year before its roots spread too widely and you will successfully prevent it from becoming established in your landscape. You can also determine if it is one of the desirable trees mentioned above, or perhaps another tree. You can take samples of leaves to your local NMSU Extension Service agent next year as growth begins, along with a picture of the color of the leaves this fall, for help in identifying your seedling tree.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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