The risks and profitability associated with four early planting dates, and three different types of bolting risk reduction strategies, were evaluated for Quebec celery production. The four planting dates studied were April 17 th, April 24th, May 1st and May 8 th. The impacts on yield if plants were harvested after eleven week, twelve, thirteen, and fourteen weeks in the field were investigated. The three risk reduction strategies considered were plants grown from planting until June 2nd with no row covers, under floating row covers of spunbonded polyester (Agryl P17, Plastitech) and under floating row covers made of clear, perforated polyethylene (Plastitech). The results suggest that the floating row covers can help plants reach the required market standards sooner that if no row covers were used from the planting date investigated until June 2nd. At the earliest two planting dates, the results suggest that row covers may significantly suppress bolting and allow greater yields at earlier harvest dates. The results also suggest that row covers may provide an advantage at later planting dates, as they may allow for the plants to reach marketable standards sooner. The results also suggest that there is a 50 percent chance of encountering bolting rate of 30 percent or higher if transplanting plants on April 17th. The row covers reduced the probability that plants will bolt to close to zero at for all four planting dates. The most profitable strategy was determined to be planting on April 17th, growing the plants under row covers made of spunbonded polyester (Agryl P17, Plastitech) from planting until June 2nd and then harvesting after the plants had been in the field for thirteen weeks.

Vernalized celery seedlings (Apium graveolens L. var. Florida 683) were predevernalized under different temperature and light regimes prior to field transplanting. At least 89% of predevernalized plants bolted during both 1999 and 2000 suggesting that the predevernalization treatments were not effective in counteracting the vernalizing stimulus. Predevernalization treatments had no long-term effect on growth and development. Non-vernalized celery seedlings were transplanted on clear polyethylene mulch, thermo-selective polyethylene mulch or no mulch in combination with clear perforated polyethylene mini tunnel, single or double layer of agrotextile mini tunnel or no mini tunnel. Very few plants bolted in 1999. Mulch increased fresh weight and number of celery leaves compared with controls. Plants grown on clear polyethylene mulch had significantly higher mortality rates than other treatments. Agrotextile mini tunnels reduced bolting to 0% in 2000. Mini tunnels, especially a single layer of agrotextile, increased fresh weight, plant height and stem diameter in 2000.

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