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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. Akin to a potentially useful time capsule with some benchmarks. 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 and my Feb 2020 Rant for more specifics and become familiar with the Law of Independent Events). Moreover, the "its supposed to be" commonly heard from TV weather people regarding specific predicted temperature is based on faulty reasoning (i.e., BS) and their forecasts are often significantly inaccurate (i.e., educated guesses). While the grill is hot, the Farmer's Almanac predictions based on previous averages are hogwash!

 

The wise person will study and learn from history. That being said, climatic norms no longer exist (the divergence started around 1990 and data previous to this is now largely irrelevant), 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 Mar 2020 and Oct 2017 Rant of the Month.

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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. 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 university computer assisted project primed for the doing. When our plants exhibit abnormally one understandably is tempted to speculate but the reason is often or sometimes not a single cause or a simple answer.

 

A related gardening factor that is largely ignored is soil temperature, 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. Moreover, it is most important to know that water has a high specific heat and to understand and consider the implications. A healthy soil, one with a higher organic content, will have far less temperature fluctuation. Whereas the temperature of a degraded or impoverished soil (dirt) found in heavily human disturbed situations, including most subdivisions, 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. Pronounced temperature fluctuation creates stress which negatively affects plant health, while also favoring ruderal species.  See also Garden v House, my Jan 2022 Rant.

 

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 (F/F) and/or early fall frost/freeze

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

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

  • Affect on phenology, esp. flowering, autumn leaf color and drop

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

 

FOR COMPARISON (last 47 years, since 1975): 

  • last spring frost/freeze (32°) Apr 17 - range 57 days (Mar 24 - May 19)

  • first fall freeze/frost (32°) Oct 19 - range 43 days (Sep 30 - Nov 12)

NOTE: these events rarely, if ever, happen on the "average day" and only about 1/4 the time within the week surrounding the "average," and what happened last year is irrelevant (independent event) as regards occurrence, even though the media weather people imply otherwise

  • extreme low: mean -7.4, but -11.4 (1975-99) vs -3.9 (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

  • GROWING SEASON: mean 189 days, range 153-215 (62)

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2024 - warm Dec, cold snap mid Jan; max low -5 but only for one hours, total duration of minus temps 10 hours on consecutive days mid Jan, cold snap preceded by heavy (2-3") soaking rain (unfrozen ground) thus some mitigation; very mild winter and prolonged spring; winter/spring flowering was a week or two earlier than normal; excellent year for witchhazels; last spring frost/freeze Apr 6; not much winter take on the smooth hydrangeas

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2023 - first half of Dec was above average; sudden polar blast Xmas week, temp fell 50 degrees in 15 hours (record for the region is 56° in 24 hours), likely exacerbating damage to plants from the dry fall; another factor, while the first frost was Oct 18 it was then warm for a month so the plants had not enough time to shutdown; still dealing with the 2021 cicada damage; warm Jan-Feb, esp the min; rarely below freezing last half of Feb (71 on Feb 22, 76 Mar 1); record for fewest days held below freezing (7); cold snap Mar 17-20 (low 17°) imperiled specimens breaking dormancy esp misplaced and ill-advised species; witchhazel flowering was surprisingly poor; taxa not fairing well coming out of winter include Kerria (esp variegated), Japanese plum yew, Japanese Andromeda, Beal's mahonia, crape-myrtles, and roses; max winter low -9° in late Dec (23rd); last spring F/F Apr 23; first half of calendar spring was warmer than the second half with the advantage that this prolonged spring flowering which can sometimes be suddenly halted (forced to conclusion) by hot weather; the chilly spring ended on May 6; unusually dry late May and early June; first lightning bug June 15; very few Japanese beetles; mild summer, hot dry late, max high 94° late Aug; 17 days 90+; first F/F Oct 31 25°; ginkgo leaf fall Oct 31; growing season 191 days; annual precipitation was 20% (9 in) below average (43.6)Apr-Jun dry, dry fall; strangely, I saw several 'Endless Summer' hydrangeas in Indianapolis flowering in late Sept/early Oct

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2022 - abnormally warm Dec; mild winter like temps in early Jan; mild winter like condition mid Jan to mid Feb; min low 0° but only for a hour; only occasionally below 10°; 43° (59->16) drop in 24-hour on Feb 17-18; snowdrops & witch-hazels started on Feb 16; early dormancy break but only some light browning freeze; last spring F/F Apr 19; the damage from the 2021 emergence and ovipositing of Brood X of the 17-year periodic cicadas continues to be obvious; Fothergilla was not their fav but just about every stem that was egged died (so very susceptible); a week near 90° in early May accelerated those species that were flowering (esp tree peonies) and caused an abrupt end to what was until then a long and wonderful plant spring; less dieback on lespedeza and crape-myrtle; first firefly June 21; several weeks with temps in 90s in one early May; exceptionally hot and dry June, grass going dormant by June 21; excellent condition in 2022 for Himalayan pines; hot but not so dry continued to early August; first lightning bug June 20; first Japanese beetle June 1 but limited numbers; I rarely have to plant castor bean as it normally reseeds, not this year; Lisa and Dan Burnham (just N of Bloomington, IN) told me the same regarding their driveway common milkweed; max high 96°; xx days 90+; long dry period that began in mid Sept, fortunately with mild temps so the short-term effects were moderated, dryness resulted in horrible conditions for fall fungi and recently planted specimens; fabulous year for Himalayan white pines; according to my friend Christy Jacobi, who lives 1/2 mile N of me, pawpaw fruit production in her patch was phenomenal compared to previous years; first fall F/F Oct 18 but something of a false positive since it was of short duration, no killing freeze until almost a month later (Nov 12) then abnormally cold for a week; fabulous fall color year; atypical ginkgo fall, drawn out rather than eventful with 1/4 the leaves coming down with one wind gust on at 13:30 on Nov 4; growing season technically 183 days but in practice more like 208

 

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; overall a very mild winter; emergence of winter bulb and oriental witch-hazel flowers was about one month later than 2020 and spectacular; there was an unusually strong La Niña near the end of 2020, previously this has induced severe spring weather (did not manifest in 2021); nasty 52° swing (73->21) in 36-hours Mar 30-Apr 2; 110° fluctuation in a week (73>21>79); no wind at the low to help reduce damage; VERY fortunate the low duration was only several hours, surprisingly little damage (mostly magnolias) given the development of new growth; these dramatic swings are especially critical when going into or out of dormancy and when the low falls below freezing; FYI the record change for central Indiana in a 24-hour period is 58° but that was a Jan (1916) event (plants were dormant); temp fell below freezing on Apr 21 (26°) only for a few hours and foliar/floral damage was largely prevented by a rare 3-inch accumulation of snow; the late heavy snow load presented some unusual circumstances, while it insulated some vegetation the already emerged leaves increased the surface area for accumulation and weight breakage; elevated leaves and flowers were more damaged (e.g., asparagus, azalea, bald cypress, ginkgo, katsura, raintree, redbud, smokebush and wisteria, but only some hostas and oriental maples, and (curiously) not necessarily those with more developed leaves; for more on damage see my May 2021 Rant; emergence of Brood X of 17-year periodic cicadas was delayed by cool weather -- began at my place on May 22. the weather had turning suddenly much warmer (several days at or near 90 followed by a few days with spotty rain and much cooler temps (mid 40s at night); perhaps less relevant for plants and gardening than for the cicadas; essentially finished by June 25; heavy emergence at my place (NE Indianapolis); plants most affected oaks, maples (several oriental spp./cvs. so severely affected they were extracted), sweet shrub, beech, buttonbush, black gum, dogwood, fringe tree, hop hornbeam, katsura, serviceberry, seven sons, sweetbay magnolia; surprisingly, not ericads (except blueberry), elderberry, viburnums or most conifers; for more specifics on the cicadas see Kritsky’s 2004 book (Ind Acad Sci publications; my April (2021) rant highlights the emergence; few lightning bugs; expected a nasty Japanese beetle year given the mild preceding winter, but below average infestation; chiggers were bad, even in city; relatively wet early summer; hot dry late summer; wet fall with lots of fungi; ginkgo fall not a single day event; fall color below average and late; min low -2; max high 95; xx days 90+; last spring freeze Apr 21; late fall color change; 70 as late as Nov 9; first fall F/F Nov 2; growing season 195 days

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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); the apple crop was essentially destroyed by the late freeze; 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 94; min low 2; growing season 160 days

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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; last spring F/F Apr 1; first fall F/F Oct 31; growing season 213 days

 

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; last spring F/F Apr 29; first fall F/F Oct 21; growing season 175 days

 

2017 - mild winter; early spring, early last frost (Apr 8); 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 F/F; fall flowering PJM Rhodo ‘Elite’, Forsythia ‘Courtisol’; Nov 10 ginkgo fall; max high 93; min low 1; first fall F/F Oct 26; growing season 201 days

 

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 first F/F - Nov 12); cool wet fall; sudden dramatic temp fall in late fall, affected several woody perennials and ever-greening; ginkgo fall not on a day but spread over a week; max high 93; min low -7; last spring F/F Apr 12; growing season 215 days

 

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 winter experience for plants (throughout the Midwest) due to the duration and combination of factors; e.g., it was noticeably windier); many established plants perished; last spring F/F Apr 24; first fall F/F Oct 18; growing season 178 days

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