Flowering Control and Production of Strobilanthes dyerianus Mast. (Persian Shield)

Grown for its distinctive foliage, Strobilanthes dyerianus is a popular bedding and container plant. A problem in production is that over-wintered stock plants often flower. Once the plant becomes reproductive, stem elongation slows and floral buds arise from every node, rendering the plants useless for propagation. The objectives of this research were to examine the effectiveness of manipulating environmental factors and the application of ethephon on preventing floral bud initiation, as well as determine optimal nitrogen rate for stock plant culture.

The first experiment was performed in a glass greenhouse and ran 11 weeks, utilizing 8 h, 10 h, 12 h and a 4 h night interruption photoperiod treatments to determine critical photoperiod. None of the photoperiod treatments were significant for inhibiting flowering and there was a positive correlation between plant size and flowering. A second experiment was performed in growth chambers to create three photoperiods (8 h, 12 h and 16 h) with two temperature regimes (24C day/ 21C night and 17C day/ 14C night) for a total of six treatments. Neither photoperiod nor temperature inhibited bud initiation, and there was no correlation between plant size and flowering.

The third experiment examined potential use of ethephon to maintain vegetative plants. Six rates of ethephon (0, 150, 300, 450, 600 or 750 mg·Lˉ¹) were applied at three frequencies (weekly, biweekly and monthly) over an eleven week period. Floral initiation was not totally inhibited, but flowering was highly correlated to plant size.

Additionally, plant growth response to nitrogen was examined to determine the optimal rate for stock plant production. Plants were treated with 0, 100, 200, 300 or 400 mg·Lˉ¹ N from a 15 N – 2.2 P – 12.4 K fertilizer at each irrigation for eight weeks. There were no differences among plant quality ratings for plants receiving 100, 200, 300 or 400 mg·Lˉ¹ N, and plants grown with 200 mg·Lˉ¹ N had the largest leaf area and shoot dry weight.