You probably hadn't noticed, but while the debate over whether or not our climate is changing and our planet is experiencing a general warming trend, the nation's hardiness zone maps were reconfigured several years ago. So, as you read this while looking out over another fresh coating of snow, and feeling single digit temperatures for the umpteenth time this winter, keep a wary mind over what I'm about to tell you!
Over the past 10 or 12 years, the weather we've experienced here in the St.Louis area has been generally mild, especially our winters. Perhaps because of this, the maps were changed to reflect this overall trend. Those of us in the nursery trade, having noticed this unusual weather alteration, started to introduce to our customers, plants that had been, up until recently, only been found in more southern climates. As the new maps reflect, there exist portions of the St.Louis area that remain in a zone 5, while pockets of our city can be zoned 6 and even a few 7's. Because of this slight and general temperature increase over this period, we have introduced plants like crape myrtles, southern magnolias and nandina to this more historically northern climate. These are plants that,15 years ago, wouldn't have been offered in the plant product mix at most nurseries in our area.
We've even seen plant species like aucuba, photinia and some of the newer introduced repeat blooming azaleas respond well to what have been warmer than usual winters over the last few recent years. This winter could be, however, the one that could remind us all, why these plants are zone rated the way they are. This winter, as you know, has been atypical compared to the previous 5 to 10. We've experienced extreme cold temperatures, like we haven't seen since the late '80's. Because of this, we wouldn't be surprised to find that many of these marginal species may not come out of dormancy. Keep in mind that when spring finally does break and our soils begin their slow warm up, it will take time for these hot weather plants to respond. So, if your crape myrtle isn't in full leaf by April 15th, don't fret, give it some time. This may be the year when it dies back all the way back to the ground and it has to start over. This regrowth may not begin until some time in May after we've had consistently warmer weather. Your southern magnolia may also get nailed by these extremes. It probably is already showing signs of winter burn and much of that affected tissue will more than likely have to be removed which means your tree may be smaller than it was last year.
Situated where we are, in the middle of the country, allows us to enjoy a wide array of plant life. It makes it possible to appreciate evergreens that are more commonly found in northern climates as well as the aforementioned species more thought of as southern. But, when mother nature throws a change up, we need to be prepared to suffer what hopefully are only minor setbacks. Only time will tell, stay tuned!