Optimal Spacing of Grafted ‘Primo Red’ High Tunnel Tomato

Grafted and ungrafted ‘Primo Red’ tomato (Solanum lycopersicum) transplants were planted at 16-, 20-, and 24-inch spacing in a commercial high tunnel in central New York, USA, to compare yields. ‘Primo Red’ scions were grafted onto ‘Maxifort’ rootstocks and left to heal in a commercial greenhouse facility. Tomatoes were harvested as they ripened, and the weight and number of fruit per plot was recorded and then calculated out to a per-plant basis. Wider plant spacings resulted in higher yields for both grafted and ungrafted plants. However, economic returns remained highest in the highest density (16 inches in-row) spacing with grafted plants. This indicates that growers may not need to adjust density despite additional foliage from grafted plants. Foliar incidence of Botrytis gray mold (Botrytis cinerea) was not significantly different under spacing or grafting treatments. Grafting resulted in higher yields across all plant spacings compared with ungrafted plants. Commercial growers can use this information to make choices on grafting and spacing in high tunnel tomato.