This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. injury to Plants from Rapidly Dropping !•. Daubenmire Professor of botany, Temperature in Washington and State College of Washington, Northern Idaho Pullman Ix •ARL¾ 70 years of recorded weather history, Washington and I0 PRIEST RIVER E. E northern Idaho have on three occa- IDAHO sions experienced exceptionally 5 sharp freezes in late autumn or early winter that caused consider- able damage to plants. A brief review of these events is warranted since the records are consistent enough to permit the drawing of -5 significant conclusions. Freeze of December 1924 -I0 Aside from the actual records of daily maximal and minimal tem- -15 peratures for the freeze of Decem- ber 1924, two publications have re- ferred to its effects on plant li•e. -20 The monthly weather summaryfor Washington (7) indicated damage to .cropsover a wide area, stating -25 that there was suspectedinjury to winter wheat, truck crops, and peach spurs. On the west side of -50 the Cascadesin Washington it is possible that even native taxa were damaged. for the summary also states: "Shrubbery in the Puget Sound country is reported as dam- aged by the cold." Unfortunately the brevity of this comment robs it of mostof its fundamentalbiologic significance,for there is no i•dica- tion as to whether or not the dam- 5- age was confined to exotic "shrub- bery." In the period 1911-1917 a series of plantingsof differentgeographic races of Pinus ponderosa were -5 made at the Priest River Experi- mental Forest in Bonner County, •daho (12). Included were -I0 tions obtained from the Siskiyou and Shasta National Forests which are situated in the mild oceanic -15 climates of southwesternOregon and north central California, re- l•xo. 1.--Diurnal ranges of temperature during the unseasonal cold weather of De- spectively. The sudden drop in cember14-28, 1924. Dashesre•resent smoothedtrend lines based on monthly means, intended to approximate the average ranges of diurnal temperatures at this time temperature (Fig. 1, upper part) of year. Shading of columnsindicates temperatures below the freezing point of on December 15, 1924, when the water. 582 JO•SR•ALOr FORESTRY Siskiyou planting was eight years er regions, all with more continen- this cold wave that is also charac- old and the Shasta nine years old, tal climatesbut from placesas re- teristic of most others discussedin proved disastrous. Most trees of mote from the test location as Ari- this report is that immediately the Siskiyou planting were killed, zona and South Dakota, withstood prior to the invasion of cold air and the Shasta planting was com- the temperature drop without evi- there was a brief period of abnor- pletely destroyed. Races from oth- dent injury. A curious feaure of mally high temperatures which served to a.ccentuate the extent of the subsequentprecipitous drop. 20 Comparison of the actual tem- _ ,• MOSCOW, IDA. peratures with norms for the sea- 15 son(Fig. 1) doesnot suggestgreat- er abnormality for the coastal re- gion (as exemplifiedby Centralia) IO than for the inlandstation; yet if nativeplants sustained damage, it was confinedto the coastalregion. 5 Freeze of October-November 1935 O, In the autumnof 1935,tempera- tures prior to October 17 had not dropped lower than 30øF. in the -5- Weather Bureau instrument shel- ter at Moscow,Idaho (Fig. 2, up- per part). On the 25th, and espe- ciallyon the 26thand 27th,daily c• -Io maximal temperaturesrose well in excessof the average, then on the • -I.5, 28th a massof cold air beganto invadethe area and temperatures droppedrapidly. For a periodof z -20 five consecutivedays temperatures wereso abnormallylow that daily maximal remained below the nor- mal minimalvalues for this season, 15- I-1PULLMAN, WASH.resulting in a condition of about equal intensity but shorter dura- ..... n-nH NOV.6-ZO, 1955 tion than that which destroyed pines at the Priest River Experi- mental Forest 11 years earlier (compareFig. 1, upper half, and Fig. 2, upper half). HUH__................ Commentspublished in the then- current issues of Climatological -$ Data '(8) recognizedthis as "un- usually coldweather for so early in the season,"resulting in the cold- ø......... /........... I est November temperature since 1893. Elsewhere (9) it was stated that "damage from the early No- -15 vember freeze was considerable" also in Washington, especially to "pears in the Kennewick section, -20 sweet cherry, apricot, and English walnut trees." In the memory of _,o the writer, damageto sweetcherries -?_5 (probably mostly the Lambert va- riety) proved so extensive in the Pullman-Moscow area that many F•o. 2.--Comparison of damaging cold waves for the same area at intervals of 20 trees were cut down the following years. Moscowand Pullman are locatedabout 10 milesapart on similar topography. summer. AUOUST1957 583 Freeze of November 1955 There appeared to be a correla- then when the cold air moved in Almost exactly 20 years later tion between the degree of injury "maximum temperatures remained than the epis•)dedescribed above, and degree of age of plant and below freezing for approximately the weather phenomenon was re- seasonal maturity of leaves. A four days or longer. This was as peated. Both the maximal and young apricot tree (budded to many days with a maximum tem- minimal temperatures were well Tilton and Royal varieties) was perature below freezing as is usual- above normal the day before an in- killed while an established tree ly recorded during an entire flux of polar air brought on rapid (Wenatchee Moorpark) suffered winter." It was immediately re- freezing. For six consecutivedays negligible damage. Young Robinia ported that "lossesof strawberries, even the maxima remained below pseudoacaciathat were exceptional- raspberries, blackberries, etc., and the normal minima at Pullman, ly vigorous as a consequenceof small fruits appear to be very Washingtoni The depression was fertilization of the soll were high. Roses, shrubs, and many greater and more enduring than 20 heavily injured, whereas others ornamental trees appear to have years earlier, but the pattern was that had been forced into seasonal been killed. Nurseries suffered strikingly similar, as was the time maturity by drouth and low heavy lossesof plants. Indications of year (Fig. 2, lower half). The fertility survived. A well-estab- are that some orchards may have 1955 .cold wave was the more se- lished tree of the early-maturing been damaged in both divisions of vere, as the depression of maxima Redhaven peach escaped damage the State." This latter proved to below the normal minima was while the later-maturing Rochester be an underestimate. "There was greater, and this phenomenoncon- succumbed. Leaves of many orna- an unusually heavy drop of needles tinued for six consecutivedays. mental trees that were still green from evergreen trees" (native? According to the U.S. Weather were frozen without an absciss exotic?) "after temperatures be- Bureau (11) "new •,inimum tem- layer forming, so that they hung gan to moderate." A preliminary perature records for November on the trees through the winter. estimate of freeze damage to crops were set in many areas during this In fact, a tree of Quercus (coc- was that it "may reach 11 million freeze; the entire State had the cinea?) located at the south edge dollars" (11). A year later the loss coldest weather of record for so of Pullman retained its full com- was reappraised at 66 million early in the season,and it was the plement of dead 1955 leaves dollars. longest period of severe cold ever throughout the summer of 1956, Althou•o'h the cold wave of No- noted in the 66 years of record." along with the new crop. vember 1955 caused no apparent At the writer's home located Native plants at the site west of damage to native plants in eastern about one mile west of Pullmsn. Pullman completely escaped in- Washington and northern Idaho, Washington, 52 speciesor varieties jury. This also applies to plants Taxa native to the seaward side of of woody plants were damaged, in that had been transplanted here the Cascadeswere extensively dam- degrees ranging from slight to on the grasslandfrom'their native aged (2). Injury to native ever- complete killing. Injured patches homes in the relatively cool and green trees there was not uniform. of bark appeared to die at varyin• moist coniferous forests of the It was lighter on the windward times spread over a number of mountains a few miles to the east: sideof the OlympicPeninsula than months, these sometimescompletely Acer glabrum var. douglasii, elsewhere, lighter below an over- girdlin• and thereby killing the Berberis nervosa, Betula p•pyri- story of taller trees: lighter on distal portions of axes or branches. f era, Larix occidentalis,Pachistima northerly rather than on southerly Frequently the girdled stems nut myrsin•tes, Pinus ponderosa, slopes, lighter in the centers of out new leaves at the usual time Pseudotsu6a menziesii (Mirb.) timber tracts rather than along the followino•spring, these.crops of Franco, Sorbus scopulina. How- their margins, lighter wh•re snow leaves dying at varying intervals ever, all three of the "natives" covered seedlingsrather than hav- over the summer. that had been transplanted up- ing been blown off. Tsuga heter- By no means were all the exotics slope from drier climates (Art- ophylla was more severely damaged damaged. Many showed no detri- em,isia rigida, A. tridentata, and than was Thuja p.licata, with mental effects.e.g., pears (Bartlett, Chryso.thamnus n.auseosu• var. Pseudotsuga menziesii least dam- Winter Nellis, Sheldon), sour albicaulis), were included in the aged of the three. The evergreen cherries (Lake Duke), Picea abies, group of plants completely killed.