By Kim D. Bowman
Lemons are a relatively small part of the Florida citrus crop. But with more than 317,000 lemon trees propagated in Florida nurseries over the past two years, lemons are clearly gaining increasing interest from growers trying to find a crop that is easier to grow and with a quick return on investment.
As is the case for other citrus crops, the choice of rootstock is an important factor in determining the success and profitability of a lemon planting. Several different lemon scions are available to Florida growers. The two most common are Bearss and Eureka.
To compare rootstocks for Bearss lemon, a small, replicated rootstock trial was planted at the U.S. Department of Agriculture (USDA) Picos Farm in Fort Pierce, Florida, in November 2018. Trees were planted at a relatively high density (283 trees per acre) to provide high yield in the early years. The trees on all rootstocks appeared healthy, grew quickly and were topped to control size in 2019.
The first crop was harvested in November 2020, just 24 months after planting, with an average of about 9 pounds of fruit per tree, or 2,400 pounds of fruit per acre. There was a large rootstock influence on fruit yield, with US-896, US-897 and Volkamer yielding the best at about 4,000 to 4,700 pounds of fruit per acre. In contrast, the rootstocks US-802, Cleopatra and Swingle had the lowest yields, at about 500 to 1,300 pounds of fruit per acre.
A large portion of the lemon crop in Florida is used for juice, so the percent of juice in the fruit is an important factor to evaluate in comparing rootstocks. Interestingly, in this first harvest the rootstock did not appear to have a significant effect on percent of juice in the Bearss lemon fruit. See a table containing all reported results here.
As for trials with other scions, rootstock comparisons should be continued for at least four harvest seasons before firm conclusions are made about relative rootstock suitability for a particular situation. This Bearss rootstock trial will continue to be evaluated over the coming years, to compare longer-term rootstock effects on tree health, tree size, fruit yield and juice yield.
Evaluation of fruit quality in this Bearss trial is being conducted in cooperation with Greg McCollum at USDA. A second Bearss trial was planted at the Picos Farm in 2020 to evaluate the new US SuperSour 1, SuperSour 2 and SuperSour 3 rootstocks with lemon scion. A third lemon trial, with Eureka scion, was also planted at the Picos Farm in 2020 to identify any graft compatibility issues between Eureka and the rootstocks. All these trials are available for examination by appointment. Periodic updates to results from these and other USDA rootstock trials are posted here.
Kim D. Bowman is a research geneticist at the USDA, Agricultural Research Service, U.S. Horticultural Research Laboratory in Fort Pierce, Florida.