by Tim Baker, Northwest Region Horticulture Specialist
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In my last column, I discussed phenology, the study of the influence of climate on biological events such as animal migrations and flowering in plants. This is especially important for horticulture crops such as apples, where buds that progress too quickly may be lost in spring frosts.
Ornamental species are good subjects for phenological studies as well. One year in southeast Missouri, I noticed that the redbuds were very delayed in blooming, compared to dogwoods. In all my years of watching Missouri springs, I don’t think I’ve ever seen a dogwood bloom before a redbud. But it seemed to be happening that year, at least in Kennett where I was living. Going towards Poplar Bluff, things seemed to be normal, with redbuds blooming and dogwoods on the way. Phenology can be surprising, at times.
So I decided to conduct a short survey of other specialists around the state. Over around West Plains and Thayer, both redbuds and dogwoods were beginning to bloom, both about the same time. The agronomist there had seen this in past years, when we had seen a late, cold spring.
Further north, things were closer to normal, with redbuds blooming and dogwoods not as far along. But there was a lot of overlap that year, again probably due to the late, cold spring. Some of the reporters didn’t think the redbuds were fairing too well in the Columbia area, others thought they were ok.
So what happened in Kennett? After talking to several people, and taking a closer look at the trees, I believe that one of those cold freezes in March must have gotten the blooms. This was somewhat surprising, since redbuds are fairly hardy, and grow much farther north.
But as buds progress, they become much more tender. And while they may easily survive a given temperature earlier in the season, if they have passed a certain point in their phenological progression, they’ll get damaged at that same temperature. Apparently that’s what happened to our trees that year.
Last time, I mentioned the National Phenology Network on line. If this topic is of interest, you can sign up to contribute your observations. Go to http://www.usanpn.org/ for more information.
By the way, don’t add an "r" to phenology… phrenology is the theory that one’s mental capacities can be predicted by the shape of the skull, a popular theory in the 19th century, but I don’t think it enjoys as much favor today.