Smellmelon is an herbaceous, annual vine of the Cucurbitaceae family that it has invaded to soybean fields in north of Iran (Golestan province). Syrian mesquite is a xerophytic woody shrub of Fabaceae family which became widespread in many parts of Iran. Lesser celandine is an invasive perennial with tuberous root weed of Ranunculaceae family that has invaded to wheat fields in western Iran mainly Lorestan province. To determine cardinal temperatures of these invasive weeds three separate experiments were conducted in a completely randomized design with four replications. Seeds of Smellmelon were incubated at 20, 25, 27, 30, 35, 37, 40, 43 and 45 ˚C for 2 weeks. Seeds of Syrian mesquite after Soaking in concentrated sulfuric acid for 30 min and breaking dormancy were incubated at 15, 20, 25, 30, 35, 40 and 45 ˚C for 2 weeks. Tubers of Lesser cleandine after breaking dormancy (more than 2 weeks at 4 or 8 ˚C) were incubated at 1, 5, 10, 15, 20 and 25 ˚C for 2 weeks. Obtained data subjected to regression analysis using intersected-lines model (ISL). The results showed that the optimum temperature for seeds germination of Smellmelon, Syrian mesquite and tubers germination of lesser cleandine was 34.5, 34 and 10˚C respectively. Base temperature for germination of Smellmelon, Syrian mesquite and tubers germination of lesser cleandine estimated 24.7, 11 and 0 ˚C, respectively. Ceiling temperature for mentioned weeds also estimated as 44.5, 45.5 and 25 ˚C, respectively.

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