Effect of plant population on calendula (Calendula officinalis L.) flower production

Calendula (Calendula officinalis L.) was drilled at 3, 6, 12, 24, 48, and 96 kg seed/ha in a trial at Lincoln, New Zealand, in November 1997. Plots were divided into five equally sized sections. Fully open flowers were harvested from Sections 2 and 4 of all plots twice or three times weekly from early February to mid March 1998, after which plant population and crop biomass were determined from the same sections and seed yield/flower determined from Sections 1, 3, and 5. Plant counts increased from 9 plants/m(2) at the 3 kg seed/ha rate, to 26 at 6, 46 at 12, 101 at 24, 179 at 48, and 332 plant/m(2) at 96 kg seed/ha. Total flower yield was not significantly different at populations over 46 plants/m(2), but declined with lower plant populations. The total fresh weight (and number) of fully opened flower heads collected off each plot increased from 0.5 (164) to 1.4 kg/m(2) (650/m(2)) with increasing plant population, but did not differ at the four highest populations. Dried petals made up between 7 and 9% of flower fresh weight. Yields of dry petals/m(2) were 36 g at 9 plants/m(2) compared to an average of 89 g over the four highest plant populations. Seed weight/head was 0.78 g at 9 plants/m(2) compared to c. 0.5 g for the other plant populations. Seed yield increased with increasing plant population from 128 g/m(2) at 9 plants/m(2) to 300 g/m(2) at the three highest populations.