|Last year, at around mid-season, I had a Plain Leaf Italian Parsley plant go into flowering (bolt) here in zone 6. Being a biennial plant, I was puzzled by this, because I had started the plant from seed myself so I was certain it wasn't in its second season.
While recently reading through a Texas A&M University horticulture web page which discussed how to keep young onion plants from bolting when growing in the south (onions are also biennial), it blamed this occurance on temperature fluctuations. The young plants are deceived into thinking they have cycled through their first season of growth following a pattern of growth (warm weather), dormancy (cooler temps.), regrowth, and dormancy again.
I cannot recall the temps. my plant wentthrough last season but I believe I may have figured out the problem. I admit I often tend to push my plants to get them going early in the growing season. I'd like to hear a confirming opinion.
Could fluctuating light cycles also have an effect? I usually start my seedlings in an insulated grow box in my cellar under 24 hour flourescent lights (to keep temps 70-80 deg), then move them to windows after they get going.
|Bolting can be caused by stresses of heat, dryness, fluctuations in temperature or transplanting. When a plant is stressed, it rushes to produce seeds--to reproduce--to ensure the continuation of the species.
I would agree with the article you read from Texas A&M. It could be that by growing the seedlings indoors in the warmth, then moving outside to cooler spring weather, the plants are fooled into thinking they've been through a winter.
Regarding your lighting practices, I don'tthink I would leave the lights on the seedlings 24 hours per day. I believe 16 hrs. would be sufficient. Seedlings grow best when the temperature of the air is cool, but they receive heat from the bottom (such as that given by heating coils or a propagation mat). Incidentally, some seeds are infamous bolters...parsley and cilantro are among the worst.