Background – Persian shallot (Allium hirtifolium Boiss.) is an herbaceous and biennial plant belonging to the Alliaceae family. Seed dormancy is common in Persian shallot. Therefore, unlike most plants, Persian shallot is commonly propagated by bulbs. Effect of bulb size on the growth and yield of few plant species has been investigated previously, and their results showed that large-sized bulbs produced more seeds. Effect of gibberellin on the growth and development of different plants is well documented; however, the effect of different concentrations of this hormone on flowering, produced bulbs, and seeds is not the same. Objectives – The present experiment aimed to find out the effect of bulb size and foliar application of gibberellic acid on yield, morphological traits, and secondary metabolites of Persian shallot. Methods – A factorial experiment was conducted based on a randomized complete block design with three replications. The experimental treatments were three bulb sizes (small, medium, and large) and four levels of gibberellic acid (control, and 50, 100, and 150 ppm GA3). Results – The interaction of the treatments was significant for bulb yield, seed yield, number of bulblets, leaf area, and flowering period. The highest bulb yield (79.3 g plant-1) was related to the large-sized bulbs not treated with GA3. The application of GA3 on the medium and large-sized bulbs had a negative effect on bulb yield. The seed yield of the medium and large-sized bulbs was significantly higher than that of small-sized bulbs. Using the medium-sized bulbs resulted in the highest amount of allicin (5.76 mg g-1), whereas foliar application of GA3 negatively affected allicin content in the produced bulbs so the lowest allicin content (4.72 mg g-1) was related to the highest dosage of GA3. Exogenous GA3 at the rate of 150 ppm reduced time to the onset of flowering, and increased the length of the flowering period in all bulb size treatments. Conclusions – By increasing the con
