The Effect of Seed Sowing Date On Growth and Inflorescence Size of Echium simplex

Tower of Jewels (Echium simplex) is rare plant native to the Canary Islands that has an enormous inflorescence that regularly reaches over 1 m in length.  Production of this crop for ornamental value is challenging since it is a biennial crop and takes well over a year to flower from seed.  The objective of this experiment was to determine the optimal seed sowing date to minimize production time while maintaining plant and inflorescence size.   E. simplex seeds were sown on four dates (December 1, 2008; February 1, March 1 and April 1, 2009) with 3 replications.  Plants were greenhouse grown in Kennett Square, PA and following the seeding stage, day/night temperatures were maintained at 7/13 °C and the greenhouse was vented at 16 °C.  After February 26, night temperatures were increased to 10 °C.  All plants bloomed at similar times and all were in full bloom (all flowers showing white) by April 8, 2010.  At full bloom, plant height and inflorescence height and caliper (at widest point) were measured.  Sowing date had a significant effect on plant height and Inflorescence caliper of E. simplex.  Plants grown from seed sown on April 1 were significantly shorter and had smaller caliper flowers than plants grown from seed sown December 1.  All other treatments were intermediate and there was no effect of sowing date on inflorescence height.  More importantly, there was no significant difference for all measurements between the first, second and third sow dates.  This indicates a sowing date as late as March 1 can be suitable for the production of E. simplex and will not have a negative effect on plant height or inflorescence size.