Seasonal wage labour was rarely distinguished from the permanent one in farm-household models although it has sharply increased in developed countries. Therefore, we propose to endogenize the demand for this peculiar labour type and highlight the trade-offs for the various labour combinations on farms. We use data on fruit and vegetables farms drawn from the 2000 French agricultural census. We show that seasonal wage labour is a substitute for permanent wage employment, and doesn't entirely follow the seasonality of the agricultural activity: competition on the labour and product markets play a significant role in the employment of labour types.