A three year experiment was carried out on sandy soil with a vegetatively propagated single clone of Phyllostachys iridescens in Godollo, Hungary to investigate the effect of water availability on the number of developing and aborted shoots and the number, diameter and height of culms in a newly planted grove. Part of the experimental plot was provided with drip irrigation and irrigated 3 times a week during the vegetation period from April until the end of October in all years. The first experimental year (2010) was a moist year, while during the second (2011) and third year (2012) there was drought during spring and summer. The number of shoots that developed into culms did not significantly increase over the years in unirrigated control plants, while in irrigated plants there was a three to four fold increase in culm recruitment compared to initial values. There was no significant difference between treatments in culm diameter and culm height during the first two experimental years. However, there was a five fold significant difference in these parameters in the last year. We found a strong (R-2=0.90, P=0.001) correlation between culm diameter and culm height. Our results prove that water supply during the growing season is of vital importance to developing temperate bamboos.