Conditioning Transplants Affects Early Growth but Not Final Productivity

Prior to transplanting in the field, it is common to expose vegetable seedlings to outdoor extremes (bright light, cooler temperatures, less irrigation, etc.) to reduce transplant shock. This is often done approximately one week before planting to allow plants to better withstand field conditions. During the 2014 growing season, pepper, tomato, and watermelon seedlings were subjected to common conditioning treatments for one week prior to planting. These included cool temperatures (10°C), one half normal irrigation or fertilizer, brushing twice a day, and an untreated control. Conditioned transplants were planted early and late in the growing season to evaluate performance under cool or hot field conditions. We evaluated plant survival, early plant growth (weight, length, flowering, etc.), and productivity. While plant survival was not significantly different between conditioning treatments, cold treated pepper, tomato, and watermelon seedlings were significantly smaller 3-4 weeks after planting compared to the control or brushing. The one-half irrigation or fertilizer treatments often produced intermediate early growth responses.  However, conditioned plants were not less productive and fruits produced were of similar quality to those from untreated controls. These results suggest conditioning effects on performance are transient and may not be necessary prior to planting.