ASHS 2015 Annual Conference

Crown divisions and tissue culture plantlets are popular methods for propagating purple fountain grass [Pennisetum setaceum (Forsk.) Chiov. ‘Rubrum’]. Alternatively, culm cuttings are an economically attractive propagation method for quick liner production. Our objective was to quantify the impact of photosynthetic daily light integral (DLI), rooting medium temperature, and hormone application on root and shoot development of single-node purple fountain grass culm cuttings. Single-node culm cuttings were harvested from stock plants. Prior to sticking, cuttings received either no hormone or a hormone dip application containing 1000 mg·L^–1 indole-3-butyric acid (IBA) + 500 mg·L^–1 1-napthaleneacetic acid (NAA). Cuttings were placed in a glass-glazed greenhouse with an air temperature set point of 23 °C under a DLI of 8.0 and 14 mol·m^–2·d^–1 and with rooting medium temperature set points of 23 °C, 26 °C, or 28 °C. Cuttings were harvested at 7, 14, 21, or 28 d after initiation of treatments. In general, as DLI, rooting medium temperature, and day after stick increased, cutting pullability, shoot number, and shoot and root dry mass increased. For example, from 7 to 28 d, root dry mass of cuttings not receiving rooting hormone and propagated under a DLI of 8.0 mol·m^–2·d^–1 with a rooting medium temperature of 23 °C, 26 °C, or 28 °C, increased by 1228%, 1659%, and 500%. Whereas cuttings propagated under a DLI of 14 mol·m^–2·d^–1 and similar rooting medium temperatures, exhibited increased root dry mass of 1898%, 539%, and 1544%, respectively. Rooting hormone dip application hastened root development. For example, from 7 to 28 d, cuttings propagated with IBA+NAA, under a DLI of 8 mol·m^–2·d^–1 with rooting medium temperature 23 °C, 26 °C, or 28 °C, increased root dry mass by 1487%, 742%, and 792%, respectively. Therefore, liner pullability at 28 d was 67%, 80%, and 93%, respectively. Compared to cuttings propagated without rooting hormone and under a similar DLI (8 mol·m^–2·d^–1) and rooting medium temperatures (23 °C, 26 °C, or 28 °C), resulting pullability at 28 d was 13%, 20%, and 60%, respectively. Results indicate rooting and shoot development was hastened when single-node purple fountain grass cuttings were dipped in a rooting hormone and placed on a medium temperature of 28 °C under a higher DLI >8 mol·m^–2·d^–1.