Effect of Water Stress on Growth and Flower Yield of Big Bend Bluebonnet.

Big bend bluebonnet (Lupinus havardii) has potential as a specialty cut flower; however, little information exists on the effect of water stress on plant growth and flower development for this species. A greenhouse study was conducted to characterize the growth and cut flower production in response to water stress. Five substrate moisture treatments were created by drip-irrigating plants to near-container capacity, allowing them to dry to a predetermined substrate volumetric moisture content [VMC (33%, 25%, 20%, 15%, or 12%)], and then rewatering to near-container capacity. Mature racemes (>40 cm long) were harvested weekly. After 9 weeks of treatment, the number of harvested racemes per plant did not differ among 33%, 25%, and 20% VMC, but was lower in the other treatments. Growth index, calculated as {[height + (canopy width 1 + canopy width 2) ÷ 2] ÷ 2}, was lower in the range of 12% to 20% VMC compared with higher VMC. No difference in growth index was found between 25% and 33% VMC. Root-to-shoot ratio was not influenced by VMC. Leaf greenness, as determined by leaf SPAD-502 readings, measured at the end of the experiment, was lower in plants at 15% and 12% VMC than in other treatments. In general, growth, cut raceme yield, and dry weight of the plants in 15% and 12% VMC were lower compared with the other treatments. For maximum growth and cut flower production, plants should be irrigated at a substrate moisture content of 25% VMC or greater. [ABSTRACT FROM AUTHOR]