Effect of sowing dates and plant densities on flower yield and some important agronomical characteristics of European borage

Borage (Borago officinalis L.) is an annual plant and belongs to the Boraginasea family, that afford curative properties. Increasing people's tendency toward medicinal plants to treat diseases has conduct to and essential the cultivation of medicinal plants globally and in Iran. The production of medicinal plants like other plants is influenced by environmental factors such as sowing date and plant density per m-2. There is optimal sowing date for each crop and delay causs reducing of yield. Optimum plant density at farm is foundation of farming system (1). Thus, this experiment carried out in order to study the effect of sowing date and plant density on flower yield and some important agronomical characteristics of Borage (Borago officinalis).
A field study was conducted as a split plot arrangement based on randomized complete blocks design (RCB) with three replications at farm at experimental field of Khouzestan Ramin Agriculture and Natural Resources University, Iran during 2016-2017 cropping season. Five sowing date (15 October, 5 and 25 November, 15 December and 5 January) as main plat and four plant densities including of 6, 10, 14 and 18 plant per m-2 as sub plots comprised experimental treatment. Dry flower yield, number of flowering branche per plant, number of flowers per m2, plant height, number of leaf per plant, leaf area index, dry weight of leaves and stems and oil percent of Borage were measured. Analysis of variance and comparison of means was performed by SAS software and test (Duncan), 5% level probability. Respectively.
The result of analysis of variance showed that sowing date and plant density had significant effect on plant height, flowering branches per plant, number of flowers per m2, dry flower yield and dry weight of stems. Also interaction effect of sowing date and plant densities on number of leaf per plant, leaf area index and dry weight of leaves was significant. Delaying in sowing date decreased the majority studied traits. 15 October is the best date with 72.08 gr m-2 (dry flower yield). Increasing of plant density was reduced oil percent and increased plant height, dry weight of stems and flower yield. so that the highest dry flower yield was achieved with an average of 58.63 gr m-2 at a density with 14 plant per m-2. Sowing dates of 15 October at 18 plants per m-2 had the highest leaf area index and dry weight of leaves and sowing dates of 15 October at 6 plant per m-2 had the highest number of leaf per plant.
For the highest dry flower yield results showed that in Ahvaz climate, the best sowing date for borago was 15 October and the best planting density was 14 plant per m-2.