A study was conducted to explore how different mulches affect water use of landscape plants. Plots 4.9 m × 7.3 m, were covered with 5cm pine bark, cypress, white rock, or clay aggregate. 3 potted plants of Ligustrum japonicum (wax-leaf ligustrum) and Photinia × fraseri (red tip photinia) were placed in each plot so that the top of each pot was at ground level. 1 plant of each species was planted directly into each plot. Water loss was measured on a daily basis, both gravimetrically and using heat balance stem flow gauges, during both the 1992 and 1993 growing seasons. Stomatal conductance was measured periodically during each growing season. Surface, air, and soil temperatures at two depths were recorded. During 1992, pine bark mulched plants consistently used more water than the other treatments, as opposed to summer 1993 when the most water was used by plants over white rock. Surface temperatures of pine bark, cypress and clay aggregates were higher than those of white rock both years, by as much as 20C, while temperatures under the mulch varied as much as 5C between pine bark and white rock.
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