The use of controlled environments to produce disease-free vegetative clones of strawberry (Fragaria ×ananassa) is increasing. However, protocols for mother plant management that optimize runner and daughter plant number need to be developed. Studies have shown that decreasing the fraction of nitrogen (N) supplied as nitrate (NO3-) can encourage vegetative growth in other crops. Our objective was to identify the %NO3--N that maximized runner and daughter plant number. Strawberry ‘Albion’, ‘Fronteras’, and ‘Monterey’ were grown in 19.1-cm pots filled with a peat-based substrate. Plants were irrigated with a modified strawberry nutrient solution (Yamazaki) that provided a total of 100 mg·L-1 N. The percent of total N supplied as NO3- ranged from 0% to 100%, with the remainder supplied as ammonium (NH4 ). Runners and daughter plants were harvested after eight and 16 weeks of treatment. The impact of %NO3- on cumulative runner number was cultivar specific. ‘Albion’ was not impacted, and the overall mean was 9 ± 1 (± SE).‘Fronteras’ exhibited a quadratic response. It increased from 10 ± 2 at 0% NO3- to 17 ± 2 at 60% NO3-; the calculated maximum runner number was with 64% NO3-. ‘Monterey’ exhibited a linear increase, from 14 ± 1 at 0% NO3- to 22 ± 1 at 100% NO3-. The impact of %NO3- on cumulative daughter plant number was also cultivar specific. ‘Abion’ exhibited a linear increase, from 28 ± 2 at 0% NO3- to 37 ± 10 at 100% NO3- . ‘Fronteras’ exhibited a quadratic response and increased from 19 ± 2 at 0% NO3- to 45 ± 7 at 60% NO3-. ‘Monterey’ also exhibited a quadratic response and increased from 49 ± 4 at 0% NO3- to 90 ± 7 at 80% NO3-. Calculated maximum daughter plant number occurred at 66% and 81% NO3- in ‘Fronteras’ and ‘Monterey’, respectively. Overall, at least 60% NO3- provided robust runner and daughter plant number, but the response depended on cultivar evaluated. ‘Monterey’ and ‘Albion’ appear to prefer a higher %NO3- than ‘Fronteras’ for maximum runner and daughter plant number.
