Strawberries Grown in Soilless Substrate under Greenhouse Conditions Can Increase Winter Production in North-central Florida

Ashwin Paranjpe, Daniel J. Cantliffe, Elizabeth M. Lamb, Peter J. Stoffella, and Charles Powell

Florida is the largest producer of winter strawberries in the United States. Although highly profitable, winter production of field-grown strawberries is greatly reduced by prolonged freezing temperatures and cloudy weather. Production of strawberries in open fields is becoming increasingly difficult with the imminent loss of methyl bromide, limited land resources and scarcity of labor. High quality winter production is possible by growing strawberries in soilless substrate under protective structures. Plug transplant of short-day cultivar Sweet Charlie were grown in a passive ventilated, heated greenhouse in Gainesville, FL during fall 2000-spring 2001. Two kinds of plugs (2.5-month-old naturally conditioned plugs from Cashiers, NC, and 4-month-old force-conditioned plugs produced in Gainesville, FL), and three kinds of soilless substrates (perlite, peat+perlite, pinebark) were tested in three different growing systems. The growing systems consisted of: 1) polyethylene bags (100x17x12 cm) placed on 10-cm-wide PVC gutter sections suspended 1.2 m above the ground; 2) U-shaped corrugated plastic sheet (10-cm bottom width x 12-cm wall height with 5-cm-diameter holes) placed in PVC gutter sections suspended 1.2 m above ground level; and 3) polyethylene bags (100x17x12 cm) placed at ground level over 10-cm-wide styrofoam strips. Incidence of gray mold (Botrytis cinerea) was negligible, and more than 83% of total early/mid-season yield per plant in all treatments was marketable. Average marketable weight per fruit was 20 g and was similar for all treatments. Growing system influenced early/mid-season yield from 2.5-month-old plugs, while it had no influence on the yield from 4-month-old plugs. Growing media also influenced early/mid-season yields wherein plants grown in perlite produced more marketable fruit n umber and fruit weight per plant than those produced in peat+perlite and pinebark regardless of growing system or plug type.