Performance of ‘Marsh’ Grapefruit and ‘Valencia’ Orange Trees on Eighteen Rootstocks in a Closely Spaced Planting1,2

The performance of ‘Marsh’ grapefruit ( Citrus paradisi Macf.) and ‘Valencia’ sweet orange [C. sinensis (L.) Osb.] on 18 rootstocks was evaluated with trees spaced 3.1 × 4.6 m and planted in 1968 in a deep, sandy soil. Rootstocks had significant effects on tree size, yield, production efficiency (kg of fruit/m 3 of canopy), fruit quality and the quantity of soluble solids/tree. The largest, most productive trees were generally those on rough lemon (C. jambhiri Lush.) in contrast to the smallest trees on the hybrid C. sunki Hort. ex Tanaka × Swingle trifoliate orange ( Poncirus trifoliata Raf.). Rootstocks that showed promise for use in close-spaced plantings were Rubidoux trifoliate orange, Rusk citrange (P. trifoliata × C. sinensis) Koethen sweet orange × Rubidoux, Rangpur lime (C. limonia Osb.) × Troyer citrange, and a mandarin.