Not really. Cooling down the ambient temp in the growing area can help some. Shoot for 65 degrees max. Transplanting them into a slightly smaller container will slow them down for a few days but then they take off again.

And if they get really out of hand root short cuttings off the mother plant and pitch it.

Best way - make a note and don't start them so early next year. :)

Dave

I;d take sucker ( Lateral branch) cuttings NOW.

In your zone, and I'm not that far from you ,you wouldn't be putting out plants until AFTER your last average frost date which for you would be be mid to late May.

Lowering the temps IMO is not goung to do that much and allowing a week for hardening off it should work out just fine

What also works but is usually done when the weather does not allow for planting out is to take off all foliage on a plant leaving just a tuft of foliage at the top of the plant,

That cuts back on photosynthesis which is the way that plants form energy compounds for more growth,

Carolyn, who notes to Dave that she can't even watch Indian Wells tennis going on right now since she is prohibited from going out to the front room where the TV is . Triple Sigh,

Thanks for the advice gang. I was afraid there was nothing to be done. I will go take the cuttings today.

Next year remind me to contain my self LOL...

I will add..the seedlings are not for me but have to be ready for sale May 1st for a plant sale I run to benefit Children's Hospital in Boston

I did this last year... I just kept pottting up.. but I had only started 4 from seed (other half I bought transplants) so I had room to keep potting them up.

I think it is logical to assume that heat loving plants (such a tomatoes and peppers) to slow down in growth in cooler temperatures. It happens so often when cool spring weather lingers on and the plants(matoe & pepps) do not grow substantially. They seem to be just sitting out there. It is also true for cool crops . Even those grow MUCH slowly when cool fall weather moves in. Right now, my sweet peas have been in emerging state for the past 5 days or so. Had we had warmer weather they could have been an inch tall.
So I think cool air and soil temperatures slow down growth. I could be wrong.