Heat and drought in cities can be exacerbated by limitations on water availability for irrigation. While many perennials are drought-tolerant, decreases in bloom number and quality are common. This study has two objectives. First, does bloom number in perennials decrease under limited irrigation. Second, how does this affect the number of pollinator visits. Twenty perennials were randomly planted in twelve beds, arranged in a randomized complete block design, with three beds per block. One plant of each perennial species was planted per bed. Beds within each block were randomly assigned to one of three irrigation levels: ET (evapotranspiration) 0.6, 0.3, and 0.0. Pollinators were counted by standing in front of the plant for 60 seconds and counting each pollinator within the canopy. Bloom number was determined by counting the number of blooms on one quarter of the plant and multiplying by four. Across all species, both bloom number and pollinator visits remained the same across all irrigation levels. However, individual species had very different results. Blue mist flower (Conoclinum coelestinum) had more blooms and pollinator visits in the ET 0.6 treatments (119.4 blooms and 1.3 pollinators per plant) than the ET 0.3 treatments (75.6 blooms and 0.6 pollinators per plant), while fennel (Foeniculum vulgare) had more average blooms per plant in the ET 0.3 (64.1) and ET 0 (54.9) than the ET 0.6 (15.9), though a similar average number of pollinators per plant across all treatments. Interestingly, while blooms and soil water content across all species were not correlated, pollinators and soil water content had a moderate, positive correlation (P=0.01, r=0.49).
