Ice and Subzero Temperatures Test Olive Trees in Northern Adriatic Hinterland

Summary

Extreme cold weather in the north­ern Adriatic region has caused sig­nif­i­cant dam­age to olive groves, with ice and frost poten­tially lead­ing to last­ing injuries to trees. Growers are cau­tiously opti­mistic about the upcom­ing har­vest, with experts rec­om­mend­ing patience, proper care, and spe­cific treat­ments to help trees recover from the effects of the freez­ing tem­per­a­tures.

The first three weeks of the new year were marked across the north­ern Adriatic by low tem­per­a­tures, cold rain mixed with snow and wide­spread ice. In some areas, the extreme weather was accom­pa­nied by strong winds, fur­ther com­pound­ing the dam­age, accord­ing to experts at the Center for Olive Growing at the Agricultural and Forestry Institute of Nova Gorica in Slovenia.

If tem­per­a­tures remain below 10 °C, dam­age to olive groves can be severe. Older trees may suf­fer last­ing injuries to branches and shoots, while young trees and new growth are even more vul­ner­a­ble. Ice and frost can dam­age bark, cause leaf drop, and, in extreme cases, break branches.

This sce­nario has already played out in north­ern Dalmatia, par­tic­u­larly in the Zadar hin­ter­land region of Bukovica, where Mediterranean and con­ti­nen­tal cli­mates inter­sect. In sev­eral micro-loca­tions, freez­ing rain com­bined with snow per­sisted for two days and nights, encas­ing entire groves in ice.

“Everything was frozen solid. It’s a mir­a­cle any­thing sur­vived,” said Neno Zrilić, a young olive grower from the vil­lage of Bruška. His grove lies at 450 meters above sea level, where each tree car­ried an esti­mated 50 kilo­grams of ice. Had strong bora winds devel­oped, he said, not only branches but entire trunks could have snapped.

Growers in nearby Rodaljice are cau­tiously opti­mistic. ​“If there are no fur­ther ice storms, I believe the har­vest could still be good, as it was last year,” said Branimir Šunić, who farms more than 1,000 olive trees with his fam­ily in Bukovica and the lower-alti­tude Ravni Kotari, closer to the coast.

Šunić added that his family’s oils have won mul­ti­ple awards and that they plan to enter the NYIOOC World Olive Oil Competition in New York for the first time this year.

His neigh­bor, Mate Šunić, believes the ice may also bring unex­pected ben­e­fits. ​“There’s some truth in the say­ing that every bad thing car­ries some­thing good,” he said. While sev­eral ice-laden branches were lost, grow­ers hope the cold will reduce olive fly pop­u­la­tions and sup­press dis­eases such as pea­cock spot.

Šime Marcelić of the University of Zadar urged grow­ers not to inter­fere with the trees while ice remains on them. ​“Do not touch the ice,” he warned, explain­ing that shak­ing or strik­ing branches can fur­ther dam­age plant tis­sue. The ice should be allowed to melt nat­u­rally.

Although the dam­age is vis­i­ble, Marcelić noted that extreme cold can also be ben­e­fi­cial. Low tem­per­a­tures nat­u­rally reduce pop­u­la­tions of olive fruit fly and olive moth, while lim­it­ing the spread of fun­gal dis­eases. However, the true extent of the dam­age will only be known once veg­e­ta­tion resumes in spring.

Injuries to buds and bark may allow bac­te­r­ial entry, increas­ing the risk of olive knot dis­ease. These effects, too, will become clearer around Easter, when sap flow and new growth begin.

Marcelić empha­sized that olive trees’ sen­si­tiv­ity to cold depends on sev­eral fac­tors, includ­ing age, vari­ety, over­all con­di­tion, growth stage and the dura­tion of freez­ing tem­per­a­tures. For most vari­eties, leaf and one-year shoot dam­age can occur between −5 °C and −9 °C. Serious injury to trunks and branches is likely between −10 °C and −12 °C, while tem­per­a­tures below −15 °C can cause whole trees to die back.

In this case, dam­age from freez­ing rain was largely lim­ited to bro­ken branches in exposed areas of Bukovica. Marcelić added that frost dam­age to young trees is pos­si­ble in depres­sions and val­leys where cold air lingers.

“After such events, patience and proper san­i­tary care are essen­tial to pre­vent fur­ther decline,” he said, promis­ing con­tin­ued field mon­i­tor­ing and guid­ance for grow­ers.

Marcelić rec­om­mends cop­per-based treat­ments only once veg­e­ta­tion resumes, and tem­per­a­tures rise above 10 °C, as apply­ing cop­per in cold con­di­tions can cause leaf drop. He also advises using amino acids and bios­tim­u­lants early in the grow­ing sea­son to help trees recover from stress.

Cracked or bro­ken branches should be removed, but heavy restora­tive prun­ing should be post­poned until April or May, when it is clear which parts of the tree are regen­er­at­ing. Balanced nitro­gen fer­til­iza­tion in spring can encour­age new growth to replace dam­aged foliage.

Despite the chal­lenges, grow­ers remain hope­ful. Olive trees are cur­rently dor­mant, which reduces the risk of cat­a­strophic dam­age. Still, win­ter has only begun, and pro­duc­ers in Bukovica know that after cold win­ters, hot sum­mers, pests and dis­ease, sur­vival is never guar­an­teed.