Guess you mean that you have sown seeds. Where do you live?

I sowed seeds 3 weeks ago (probably too early). Our plant out day is May 21, although I often have to wait until June 1.

Linda

yeah that is way too early, tomatoes grow so fast..

last year i started last week of feb which was a bit early, but we had a rather early spring and planted out April 10th with temps 65-70F.. this year i started them about 2-3 weeks later (2nd week of March) and the plants are already 6 inches tall and ready to go outside, however, this year spring is no where in sight! currently there is some snow flurries and temps in the mid 30s. can't ever win and it's basically a guessing game how the season will start as it can vary year to year in drastic ways.

this year it looks to be a really late/cool spring for at least half of the US (thanks to Canada where our cold originates from). please shut your door now.. :-P

this is why i never go by last frost date because that is based on averages over the last 30 years, totally useless in my opinion. need to start taking averages from the last decade and using that as a gauge. the weather from 30 years ago does not follow the trend from the past 10-15 years or so..

on the plus side, the long term forecast show a pattern change to happen late next week with temps finally rising to near "normal" for this time of year.

The speed with which tomatoes grow as seedlings is a strong function of temperature. I regularly plant, and grow seedlings at 80F, and they're ready to plant out in three weeks. Boom.

But if you keep the temps down at 60F or so, you can keep them well-behaved for 4-5 weeks. Maybe go cooler?

Determining the optimum time between planting and plant-out simply must take seedling temperature into account. Difference between night and day.

I had to switch accounts. couldn't recover my old one.

Linda, I'm near Toronto. Growing in a greenhouse where temps hover into the 80's and by May it's almost too hot to grow them.. and yes they are from seed. Our part of CA has been nice. No snow since Feb :) recently temps have gone down slightly. Since the growing season is so short for zone 5 and 6 I always grow them in the GH until May then they go out.

Stevie, I totally agree what you're saying about last frost date. Ours is supposed to be May1-9 but everyone is scared and waits till the end of May. Usually even if it's decent out.

Dan, Yes I have noticed that too! we could probably plant even earlier using that technique. AS long as the night temps don't go below 42-45?

I'm not sure that cool temperatures for germination is a help, except in that you planted too early. The real solution is to not plant as early! Seriously, if you keep the temperature at 80F (and you plant in 4-inch cups), mark a big cross on your calendar three weeks from then, because that's when they're going out.

One advantage of warm germination is that you use less time under lights. I have pretty limited lights, and it's always a squeeze to get all my seedlings ready to go. By keeping the temperatures warm, I can get more seedlings under my lights. Let me point out, as an aside, that if you're using fluorescents, keeping things warm is easy. Just put a cover over the whole setup (like a blanket), and adjust to keep the temperature where you want it. LEDs might not do it for you, though.