CENTRAL INDIANA GARDENING ALMANAC

The purpose of this almanac is to provide a record of important annual statistics and events that relate to gardening and natural history. Occasionally I will note an upcoming event that is certain or at least strongly suspected to occur, but not long-term weather predictions as that is malarky (see Chapter 12 in my book for more specifics and become familiar with the Law of Independent Events). The wise person will study and learn from history. That being said, climatic norms no longer exist, and we should expect radical fluctuations especially during the winter to spring and fall to winter transitions as global warming continues. Gardeners should be most concerned with the extreme and abnormal conditions and duration rather than averages. The observations are from Marion County (IN) but more broadly applicable, and all temps are Fahrenheit. As always, local variation is to be expected, and the variation will sometimes be pronounced. Moreover, the years as I define them here are truncated by season rather than calendar because from a gardening perspective it seems logical that winter should include the preceding Dec; i.e., Dec + Jan, Feb . . . thru November. Lastly, and the main reason for this almanac, know that the condition of your plants may be as much or more the result of what happened previously and a cumulative and multi-factor response; likely also impacted by whether or not established (i.e., how long ago planted) and if already stressed. Alas, sometimes it is hard to ascertain the cause-effect relationship or to understand that the condition you witness is often just a symptom. See also my Feb & Mar 2020 and Oct 2017 Rant of the Month.

One should be careful drawing inferences about gardening based merely on the extreme temperature, or the average of same -- such as the USDA Hardiness Zones. The situation is often far more complicated. For example, an extreme low of -2° for two separate years might lead you to believe the winters were comparable. Yet, for one of those years the visit to -2 may have been brief, perhaps only a few minutes or hours (like 2021) in an otherwise warm year, or it could have been a particularly cold winter (a much lower average) minus a trip closer to the thermometer bulb. We have the ability to truly judge a season or year from a gardening perspective, but it will require considering multiple factors, not just temperature. A special advanced university project primed for the doing.

 

A related gardening factor that is largely ignored is soil temperature and how much it can fluctuate, and why. The ignorance is not surprising given that it involves the most overlooked and least understood part of the plant -- the root system. Soil temp is directly linked to hydration which is in turn linked to soil organic content. Water has a high specific heat. The temperature of a healthy soil, one with a higher organic content, will have far less fluctuation. Whereas the temperature of a degraded or impoverished soil (dirt) will fluctuate wildly because it often lacks the hydration that provides a moderating geothermal connection. Gerould Wilhelm refers to the extremes of this swing as chills and fever. This oscillation has direct bearing on what kind of plants can be grown. High temperature fluctuation creates stress which negatively affects plant health, while also favoring ruderal species.

 

GENERAL OBERVATION EMPHASIS

  • Rapid temperature drop, esp. if not primed

  • Long dry or wet period

  • Max summer high & Overall hotness of summer

  • Min winter low (by season*) & Overall coldness of winter

  • Long cold winter period, esp. if windy

  • Dormancy breaking warm period late winter/early spring

  • Outside or regional event that affected climate (e.g., El Niño, volcanism)

  • Late spring frost/freeze and/or early fall frost/freeze

  • How growing season was affected (length & impact on performance)

  • Prevalence of disease(s) or infestation(s)

  • Autumn leaf color and drop

  • Seasonal aberration(s) & Special occurrence(s)

 

FOR COMPARISON (last 46 years, since 1975): 

  • last spring frost/freeze (32°) Apr 17 - range 56 days

  • first fall freeze/frost (32°) Oct 19 - range 44 days

NOTE: these events rarely, if ever, happen on the "average day" and only about 1/4 the time within the week surrounding the "average"

  • extreme low: mean -7.4, but -11.4 (1975-99) vs -3.8 (2000-present) a 1.5 USDA Hardiness Zone difference

  • extreme high: mean for the same years was little different and inversely related (95.2 to 94.5)

NOTE: only 8 years did the winter low not reach at least zero, 7 of these since 2003; moreover, the range for the extreme temps is significantly different -- extreme low (39) -27 to 11 vs extreme high (17) 89 to 105

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2021 - unusual and consistently mild January; typical winter conditions appeared for two weeks in mid Feb, but mitigated by snow cover; min low -2 but only for a few hours on one morning midwinter; the emergence of Brood X of 17-year periodic cicadas will have a profound effect on new growth of many woody plants many of which already will be stressed from the May (2020) freeze and the late summer (2020) drought; those properties favoring birds may be somewhat less affected by cicada ovipositing due to predation (for more specifics on the cicadas see Kritsky’s 2004 book, Ind Acad Sci publications) my April (2021) rant will highlight the emergence

2020 - very mild winter, max low 2°and only briefly; setup for Apr 18 last frost/freeze (would have been the first time in 45 years that it was on the current average date) then a late vortex, 28° for several hours on May 9 (only the 6th May freeze during last half century); most affected plants - oriental maples (esp. red weeping cultivars), ginkgo, arborvitae (bronzing of some parts), irises (causing some to bloom in early Nov); 3-week dry spell in early June and longer period late Aug into Oct (nearly 60 days with only trace precipitation); few lightening bugs, moderate number Japanese beetles; prolific year for large asteraceous plants, e.g., compass plant; sparse cone production on conifers and, as I previously suggested, the phenomenally heavy cone production in 2019 was indicative of stress as some of the plants presented damage or died in 2020; almost no black walnuts after a bumper crop in 2019 and few sweet gum balls; some species/specimens damaged by the May 9 freeze may show long-term negative effects (somewhat tied to potential stress leading into 2021 growing season); 32° on Oct 16 and 28° on Nov 2, but growing season was only partially ended (many temp sensitive plants were not killed); early, prolonged and late fall color made somewhat less impressive by the lingering effects of the late spring freeze; typical ginkgo one-day leaf fall heavily impacted by a freeze/frost event and high wind, still had partial fall Nov 9 but primary drop occurred Nov 14 with temp of 27° and high RH; unusually warm early Nov, 77° on Nov 10 (was only 8° one-year earlier); max high 93; min low 2

2019 - very mild early winter thru mid Jan (lowest 15° in late Jan 15, rarely below 20°) then two short duration polar vortices, the first 2° (Jan 15) the second in the late Jan (30) -11° but 73° warmer 4 days later (Feb 3); 45° drop (59-14) in 14 hrs Feb 7; wet cool spring; first dry spell 1st week of June then continuously wet until last week of June; moderate spring and early summer temps; very dry Sept; do not remember a year with more cones on conifers (conditions did no seem problematic but I suspect stress induced reproduction); Nov 1 ginkgo fall (but fell green); super cold early (8° Nov 11) with plants not yet dormant, lots of marcescence; max high 94; min low -13

 

2018 - severe early winter (Jan), winter burn, max low -1°; no extended dry periods during the year; not exceptionally hot; horrible population of Japanese beetles; early cold spell (mid Nov) temp suddenly in the teens killing many leaves on stem before normal senescence (normal shutdown interrupted); short growing season; Nov 9 ginkgo fall; max high 95; min low -1

 

2017 - mild winter; early spring, early last frost; off cycle emergence of 17-year cicadas; lots of Japanese beetles & lightening bugs; high rainfall spring early summer; dry late summer/fall; lots of foliar fungal diseases; mild summer temps (fall in summer); great year for solanaceous plants; Oct 26 first frost/freeze; fall flowering PJM Rhodo ‘Elite’, Forsythia ‘Courtisol’; Nov 10 ginkgo fall; max high 93; min low 1

 

2016 - mild winter; ample rainfall; lots of foliar fungal diseases; lots of Japanese beetle & lightening bug; flooding and wind damage late August; long growing season (late frost); cool wet fall; sudden dramatic temp fall in late fall, affected several woody perennials and evergreening; 1st frost Nov 9; ginkgo fall not on a day but spread over a week; max high 93; min low -7

 

2015 - few Japanese beetles or lightning bugs; cool wet fall; Nov 9 Ginkgo fall; an exceptionally long cold winter which was devastating to lots of plants; many in the gardening community refer to it as the Polar Vortex Year; max high 94; min low -15 (not close to the record, nevertheless a brutal experience due to the duration and combination of factors; e.g., it was noticeably windier)