The implementation of an evapotranspiration–based control algorithm for misting control during poinsettia propagation requires accurate estimates of resistances to the diffusive process at the canopy surface. The canopy surface resistance (rs) and the canopy stomatal resistance (rc) of fully rooted poinsettia cuttings in controlled environmental conditions, as affected by incident radiation (Ri) and air vapor pressure deficit (VPDair ), were determined from measurements. To create a model for rs, the Penman–Monteith equation was inverted and used with environmental measurements, while rc was estimated from porometer measurements. The canopy surface resistance was unaffected by VPDair under dark conditions, and a constant value of 363 (
8) s m –1 can be applied over the range from 0.5 to 2.5 kPa. Under light conditions, it was found that the canopy surface resistance depends on incident radiation alone. A non–linear equation was fitted to the experimental data and showed that 93% of the rs variability was accounted for by Ri. The canopy stomatal resistance estimated from porometry measurements was sensitive to both incident radiation and air vapor pressure deficit. Because of the lower precision of the porometer method used, only 71% of the rc variability was explained by Ri and VPDair.