Spanish-type C2 and virginia-type NC 4 peanut plants were compared in 9H (9 hours light phase and 15 hours dark phase) and 9H + 3 (9 hours light phase with 15 hours dark phase interrupted with 3 hours of low intensity light) photoperiods. C2 tended to produce greater plant weights and increased numbers of flowers in long-day treatments when compared to short-day treatments but peg growth, fruit per flowers, fruits per plant, and seed weights were drastically reduced in 9H + 3 photoperiods. NC 4, on the contrary, had only slight reductions in reproductive efficiency when exposed to long days. C2 plants produce more early flowers, less pegs per flower, but more fruit per peg than NC 4 plants in 9H photoperiods. F₁ plants from crosses between C2 and NC 4 had approximately the same plant weights as the NC 4 parent, but significantly greater reproductive efficiency than the virginia-type parent when grown in 9H light treatments. Neither the position of the peg on the plant nor the light treatment of the maternal parent appeared to influence peg growth on F₁ plants. Significant differences in the growth of pegs bearing F₁ embryos from reciprocal crosses were noted, however. F₂ plants were selected from 9H, 9H + 3, and 15H light treatments which produced more virginia-type fruits and more pegs per early flower than the NC 4 (virginia-type) parent.