This month the "Plant of the Month" topic is about a tree which may be in the forefront of your minds right now: Acacia smallii. If you have purchased a smallii in the past year and it now appears to have frozen, you may be the victim of an uncontrollable genetic mix-up.

What you have is not a smallii. It is an Acacia fernesiana. These two acacias are genetically interlocked. Amazingly enough, if you were to plant beans from a smallii, what would grow might be either a smallii or a fernesiana...and vice versa. Their genetic similarity results in very few visible differences. However, if ignored, those differences can lead to disastrous results. As previously mentioned, the fernesiana is very frost sensitive. Additionally, it blooms in the fall as well as in the spring. The smallii, on the other hand, tolerates frost very well, and blooms only in the spring. (An interesting note: the smallii is larger than the fernesiana.) Fernesianas do very well in Phoenix or Yuma. But, in cold Cochise County, they just don't make it...even in Tucson they freeze back every year.

If the smallii were not such a beautiful tree, perfect for an arid landscape, I would say, "Don't mess with it!" But, it is beautiful. It grows to a height of about 35 feet with dark brown, beautifully textured bark, lacy fine foliage, and long straight white spines. And, it is perfect for an arid landscape because of its tolerance to both the hot desert sun and drought conditions. The smallii is an excellent tree for a patio or as an accent tree in a landscape.

What can be done about the fernesiana if you choose a smallii for your landscape? First, check with your nursery to see if they have had the plants for more than a year. If they have, and it is a reputable nursery, then they have probably weeded out the fernesianas. Second, wait until fall to purchase your smallii (choose one that is not blooming), wait until spring (around May or June) before planting...just to be on the safe side. Now, if you planted what you thought was a smallii in the spring and it is still blooming in September, check with your nursery to see if they will take it back or exchange it.

In spite of what may appear to be serious problems, the smallii is such a beautiful landscape tree that it is well worth the trouble.