Effect of Reduced Irrigation on Growth and Flowering of Coneflower and Sneezeweed

Abstract

<jats:p>Reduced irrigation (RI) can be used to reduce irrigation volume as well as to control plant growth. The timing and duration of RI applications can affect overall plant growth and flowering. Knowledge of plant response to RI can allow growers to control growth and plant form. The objective of this study was to quantify flower and overall plant growth of ‘PAS702917’coneflower (<jats:italic>Echinacea purpurea</jats:italic>) and ‘Helbro’ sneezeweed (<jats:italic>Helenium hybrida</jats:italic>) in response to RI. A soil-moisture sensor automated irrigation system was used to apply four irrigation treatments: RI and well-watered (WW) controls (25% or 38%) and two alternating treatments to apply RI for either the first 2 weeks (25% followed by 38%, RIWW treatment) or final 4 weeks (38% followed by 25%, WWRI treatment) of the 6-week study. For the sneezeweed experiment, RI was reduced to 20%. For coneflower, peduncle length was greater for the WW (36.8 cm) and RIWW treatments (35.7 cm) than the RI (27.0 cm) and WWRI treatments (26.6 cm). Shoot dry weight, compactness, leaf area, and flower number were not significant. For sneezeweed, WW plants were taller (57.2 cm) and had greater shoot dry weight (49.8 g) than plants in other treatments. WW plants also had more flowers (99) than WWRI (63) and RI (67) plants, which were more compact. Total leaf area did not differ between treatments for either species. Total irrigation volume was greatest for WW plants (5.2 and 15.1 L/plant for coneflower and sneezeweed, respectively), with RI at any point during the experiment resulting in water savings.</jats:p>

Fertilizer Rate and Substrate Water Content Effect on Growth and Flowering of Beardtongue

“…The effect of fertilizer rate was greatest at low VWC with no difference at the 40% VWC threshold. In contrast to this study, leaf greenness of H. hybrida was greater for plants receiving a RI treatment compared to WW plants but similarly there was no effect of irrigation treatment on SPAD readings of E. purpurea [30]. For H. hybrida, it may be possible that the excessive growth of plants at receiving the WW treatment resulted in depletion of available nutrients in the substrate and subsequently, resulted in lower SPAD readings.…”

“…Water use efficiency was greater for plants receiving the RI treatment than the WW treatment. This result is similar to that of sneezeweed, which also had greater WUE at RI than WW, but differs from coneflower which was not affected by treatments [30]. These results indicate the RI treatments not only result in water savings, but are beneficial for production and salability of plants.…”

“…For Radrazz flower number was reduced by 27% and 85% for the 20% and 10% SMC and for Belinda's Dream flower number was reduced by 42% and 75% at 20% and 10% compared to the 30% SMC treatments. Number of flowers for Helenium hybrida 'Helbro' (sneezeweed) was greater for plants grown at 40% VWC compared to 20% VWC and there was no difference in flowering of Echinacea purpurea 'PAS702917 for plants grown at 25% or 40% VWC [30]. The variability in fertilizer and irrigation treatment on flowering suggests differences in plant water and nutrient requirements, adaptation features, and degree of water stress imposed by the reduced irrigation treatments.…”