Dynamics and flowering period of plum varieties

U Republici Hrvatskoj šljiva zauzima drugo mjesto kod voćaka po površinama i proizvodnji plodova. Sorte šljiva zastupljene u hrvatskim voćnjacima često su tržišno neatraktivne ili su osjetljive na virus šarke te je njihova proizvodnja i plasman plodova nekonkurentan. Cvatnja je važna fenofaza kojoj treba posvetiti posebnu pozornost u nasadima, jer ona izravno i neizravno utječe na urod. Zbog klimatskih promjena voćke su tijekom cvatnje izložene povećanom riziku stradavanja cvjetova od nepogoda (mraz, suša, vjetar i sl.). Istraživanje je provedeno u pokusnome nasadu šljiva na pokušalištu “Jazbina” Agronomskog fakulteta Sveučilišta u Zagrebu tijekom proljeća 2020. godine. U radu su istraživane dinamika i razdoblje cvatnje 7 sorata šljive 'Haganta', 'Toptaste', 'Topgigant', 'Topfive', 'Topfirst', 'Jojo', i 'Elena' cijepljenih na podlozi WaxWa. Za određivanje fenofaze cvatnje koristila se BBCH skala pri čemu se utvrdio početak cvatnje i puna cvatnja. Za izračun potrebnih suma toplinskih jedinica od mirovanja do fenofaze cvatnje korišteni su podaci obližnje meteorološke postaje. Sorte su se razlikovale po vremenu od početka do pune cvatnje. Utvrđeno je kako od istraživanih sorti najranije kreće Haganta (16.03.) dok je najkasnije s cvatnjom započela Topgigant (24.03.). Tijekom 2020. godine neposredno nakon pune cvatnje zabilježene su niske temperature koje su prouzročile smrzavanje cvjetova.In the Republic of Croatia, plum ranks second in fruit trees by area and fruit production. Plum varieties represented in Croatian orchards are often unattractive on the market or are susceptible to the plum plox virus (PPV), so their production and fruit placement is uncompetitive. Flowering is an important phenophase to which special attention should be devoted in orchards because it directly and indirectly affects fruit yield. Due to climate change, fruit trees are exposed to an increased risk of flowers being damaged by disasters (frost, drought, wind, etc.) during flowering. The research was conducted in an experimental plum orchard at the experimental site "Jazbina" of the Faculty of Agriculture, University of Zagreb during the spring of 2020. The dynamics and flowering period of 7 plum cultivars ‘Haganta’, ‘Toptaste’, ‘Topgigant’, ‘Topfive’, ‘Topfirst’, ‘Jojo’, and ‘Elena’ grafted on WaxWa rootstock were investigated. The BBCH scale was used to determine the phenophase of flowering, determining the beginning of flowering and full flowering. Data from a nearby meteorological station were used to calculate the required sums of heat units from dormancy to the flowering phenophase. Varieties differed in time from beginning to full flowering. It was determined that Haganta started earliest of the researched varieties (March 16), while Topgigant started flowering at the latest (March 24). During 2020, low temperatures were recorded immediately after full flowering, which caused the flowers to freeze