Comparing Culture and Planting Times for New Cultivar Releases of Rutgers Scarlet Lettuce®

Two new, red lettuce cultivars touting high levels of anti-oxidants were trialed in Central New Jersey. Growth assessments compared spring versus fall planting times, plasticulture versus bare ground culture, and field grown versus greenhouse production.  Pelleted seed and transplants of the Rutgers red leaf and red romaine cultivars termed Rutgers Scarlet Lettuce (RSL) were planted in replicated plots plasticulture or bare ground 12 inches apart in double rows on a 28 inch bed with trickle irrigation. 

Spring season germination of field sown seed on white plastic averaged 63.3% for RSL leaf lettuce and 65.0% for RSL romaine. On black plastic, RSL leaf cultivar averaged 42.5% germination and RSL romaine 35.0%. Fall germination on both black and white plastic trended lower at 30.0% and 25.0% for RSL leaf and 55.0% and 55.0% for RSL romaine, respectively.  Seed germination for greenhouse transplants in 50 cell trays was 96% or better in both spring and fall plantings which was significantly better at P> 0.05 than all field plasticulture and bare-ground treatments.  This result was largely due to differences in soil temperature of a constant 80⁰ F. from radiant floor heat with indoor cultivation vs. a variable field soil range of 48.5-69.6 ⁰ F. in the first 21 days after seeding.   

Wet head weight from spring bareground trials for Rutgers Scarlet Leaf and Romaine averaged 232.6 and 246.0 grams, respectively.  Wet head weight for RSL leaf lettuce in plasticulture averaged 138 grams compared to a standard red leaf cultivar Red Sails average of 195 grams.  RSL romaine in plasticulture had an average head weight of 110 grams while standard green romaine was 204.1 grams.  Other comparative cultivars generally grew larger as a semi-red romaine cultivar and red leaf lettuces as Ruby Red and Tasty Red. There was no significant difference in germination, growth or yield between plasticulture colors. Late season bolting and a range of bitterness was evaluated in both the spring and fall field plantings of RSL lettuces. Both seasons were characterized with periods of rapid air temperature changes from low 60⁰’s F. to high 90’s⁰ F.  In eight separate plantings in two hydroponic operations with controlled climate, the quality of RSL lettuces were superior to field production with little to no bolting or bitterness.