PHENOLOGY & COLOR

I ended last month's essay with a reference to pretty colors of fall. I will expand on both (hue and season) shortly, but first want to throw this general comment at you. A sentiment every gardener should ponder.

GARDENING CAN BE AND IS MORE THAN VISUAL AESTHETIC

I say that even though the majority of gardening interest and plant choices are flower and color based. Yes, we all use appearance, especially color, when deciding which, where and with what, but gardening for me is much more than that. The in-your-face physical is nice, but plants and gardening have a lot more to offer for anyone willing to take notice, greatly deepening the experience having done so. I especially find the life cycle and generational diversity among plants fascinating, never mind the ecology.

Another gardening pursuit I enjoy is observing and keeping track of the changes and events, such as flowering and when specific associated organisms arrive -- then the interaction and trying to discern why and how. The term used to describe the study of this sequential, periodic and cyclical activity is PHENOLOGY -- the prefix derived from Greek and meaning to show or appear. Related, most of us want to think that "our world" is stable and reliably consistent, be that climate or when plants do their thing(s). And that's certainly the message the pretty weather people shovel us -- you swallowing because you want to believe. It must be true and useful. Think again. Yes, one can find some finely timed behavior, and the vegetative changes are sequential, but as for a fixed can set the clock or calendar by it, not that much, unlike most things celestial. It is also easy to see that these garden happenings are influenced by climate variation with temperature being a prime factor. And, as you may remember from basic high school science, temperature affects the rate of a chemical reaction, and plant physiology (which includes color) is all about chemical reactions. In fact, chemistry underlies everything but it's a realm of the mind, with most people unable or unwilling to know.

Returning to climate and phenology -- Even before we started experiencing the dramatic and ongoing increase in mean temperature, which based on accumulated data became obvious in the late 1990s, there was still lots of climatic fluctuation. Some years earlier, some years later and, if one keeps track of when and how much, patterns and trends can be determined along with causal relationship. Furthermore, while the precise date may change, the activity itself (say open for business flowering) can still be assigned a season (e.g., late spring). And occasionally the plant's name is based on this timing like mayapples and juneberries, although the name may no longer apply. For example, for several years now juneberries (Amelanchier) have been ripening earlier in central Indiana to the point that this year it was around Mother's Day (mid May). Mayberries? I have noticed the change and maintain a database of when flowering and other overt activities start at my place -- each month is divided into thirds (10-day blocks) with the individual species or cultivar then ordered accordingly within the period. While the sequencing has remained about the same, when the activity starts and stops is changing. This is not surprising since many of the changes we witness in the garden are weather and climate related. I intend to post that garden phenology list on my website later this year, adjusting it when necessary. Since history is helpful, I also maintain a gardening ALMANAC on this website. Perhaps you should consider giving it a look, maybe even start one for your region? -- BTW The Old Farmer's Almanac is a waste of time and $ (see my Feb 2020 essay).

The climate surrounding our warming planet is becoming more unstable and atypical compared to the recent past. If you were to check for the Midwest, and I have, the difference between the two most recent quarter century blocks (1975-1999 vs 2000-2024) is profound. Not only is the mean changing (the when of the thing) but so is the transition -- for the climate especially spring and fall, and for plants the change itself (i.e., aspects of the type and duration). And it's not just temperature. We exist in and are part of a system (abiotic and biotic components) with each species and abiotic factor affecting one another, sometimes in a way(s) we don't understand and may never understand. I FIND THAT SOMEHOW PLEASING. Kant referred to it as noumenon (the thing-in-itself) unknowable because we are limited by our minds and senses -- with some of us more limited (less capable and perceptive) than others :)

One of the most anticipated plant events of the year, a sort of grand finale, is the fall leaf color period. Again, every year the timing and quality of the peak color is different. Some years a little, other years more, and precipitation is a key non-genetic (and abiotic) factor that affects the fall color display. Long dry stretches in mid-summer to early fall can impact the intensity of coloration as well as the total amount, thus the overall quality. The amount of water available to the plant in the preceding weeks and months (like this year) can amplify the color, or it can reduce it -- for some specimens and species preventing it altogether. But remember, (1) you cannot "undamage" leaves and (2) brown is a color too, why not enjoy it? -- A few Midwest hardy perennial plant species change foliage color (in fall and over winter) without the leaves dying and shedding. Can you name one other than Juniperus (junipers)?

One of the most dramatic fall color changes in my garden features a decade-old hybrid witch-hazel (Hamamelis x intermedia) -- a cultivar known as 'Diane,' with her characteristic somewhat smashed form (which see). She and other related cultivars have rich green crinkled potato chip-like leaves throughout most of the growing season, but 'Diane' has a very special finishing trick. When fall arrives her leaves start changing to a beautiful mixture of yellow to burgundy (top pic) and ultimately transform into a visible from space electric scarlet (see middle pics), with a gold margin to boot. The transition period varies by year but generally lasts close to a month, start (green) to finish -- which includes leaves having fallen with the fire subsequently extinguished. However, in 2021 there was no hint of red in the fall color, instead the leaves turned completely golden-yellow (see bottom pic above). While the inconsistency (and the deprivation that year) would bother some people, I like yellow too and found the abnormal behavior supremely interesting. Why the variation, I may never know ("can't" :) again), although we did have a very unusual late April 6" snowfall, after the leaves had developed, and then a massive and damaging emergence of periodical cicadas three weeks later. My witch-hazels were not spared from the ovipositing -- the sort of data I note in my ALMANAC, Finally, as if the outstanding color wasn't enough, this magnificent witch-hazel hybrid flowers in mid-winter, and those of you savvy about floral evolution will not be surprised by the fact that 'Diane's' flowers are bright red (see pic below, backlit). Should you want more info on witch-hazels, checkout my Feb 2022 essay. -- FYI the specimen pictured was 11' wide 5' tall, growth rate @6" annually. Witch-hazel is as much shrub, and never more than a small tree. Interestingly, for some reason my resident squirrels have discovered the witch-hazels. They systematically removed every fruit off my dozen specimens but, impressively and thankfully, did little pruning damage in the process. Whether their action will impact this winter's flowering, I will know in a few months.

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Since climate and temperature were emphasized in the essay this month, consider this. -- The first frost/freeze (F/F) of fall is very significant for gardeners as it marks the end of the growing season and impacts many of our plants. At my place in Indianapolis (the middle of Indiana), the average (the mean) date for the first F/F over the past 50 years is October 20, yet it has been on October 20 only once in those 50 years. But that statistic or what date it was last year does not matter with respect to what will happen this year. Why? It's called The Law of Independent Events. But you can be sure that the pretty weather people will continue to push the average. In case you are interested, the 50-year range for that event (first F/F) is 53 days. The earliest has been Sept 30, but last year was Nov 21, a pronounced deviation). Even if one means "about that date" expanding to include three days on either side, thus Oct 17-23, it would be a losing bet since it only happened 14 times within that week (28% of the time). Moreover, while I use 32 degree air temp as the marker, frost can occur above that temperature and its possible not to freeze at 30 degrees. As I noted above, there are other factors in play (e.g., wind speed, cloud cover, RH, soil moisture, topography, and proximity to heat sinks). BTW I include the climate data in my ALMANAC. Another fun and interesting part of my gardening experience.