Non-gardening boyfrined would like to try growing heirloom tomatoes next year. i always just grew early bearing hybrids. I hear that sometimes the heirloom ones don't do so well in our cool-nighted climate. Is it the air temperature or the soil temperature that causes them to not set fruit? Was considering experimenting with a compost-heated bed and/or cold frame.

Thanks!

-E!

It is the air temperature that can affect blossom setting.

Some varieties to look for are Glacier, Mountain Princess and Nepal. Annapolis seeds might be a good resource for you.
Have a great learning adventure.

It is the air temperature that is tied to lack of fruit set (aka Blossom Drop) - see link below. But it makes no difference if they are hybrids or heirlooms. Both are subject to the same environmental effects so if you can grow hybrid varieties then there are plenty of heirlooms you can grow too.

Dave

I grew Cherry Chocolate (Chocolate Cherry?) last year, and it tasted better in cool fall weather than in our hot summer.

If he wants you to grow them, make sure he does the grunt work in the garden. I've tried maybe ten heirloom types, and never got more than five toms off any one plant.