Hi Bill - if you are passionate about lettuce here are 2 short videos on how to grow in a high density fashion. May enable you to get more of what you love! These are both videos specific to lettuce growing, from the MIGardener series.

https://www.youtube.com/watch?v=L1_Nz8AdTW0

https://www.youtube.com/watch?v=FWeFH1MVHko

Welcome to Garden Web Bill! Can you define what you consider 'warm-hot' weather that Summertime was able to withstand. What may be considered hot in the north may be considered pretty mild in the deep south. I live here in the middle of the country and we can often be around triple digits in July and August and if Summertime can withstand that I would be very impressed!

I grow mostly romaine and mini romaine types and have also grown Muir, and Nevada which are both pretty heat resistant but can't take our mid summer temps here.

I agree about telling where you live. I tried iceburg last summer and it was a flop. I do raise butterhead both spring and fall.

There are some romaines from Israel that do well.

I liked "Winter Density" (a butterhead) and "Devil's Tongue" (red deer's tongue) for winter growing. The aphids devoured the butterhead but left the Devil's Tongue alone.

I live in central Pennsylvania. Warm - hot to me is upper 80's to mid 90's. We don't see triple digit temps here. I have grown Nevada also and I liked it too. Thanks to all for the comments.

Most productive for us is New Red Fire (six cuttings and stands up to 90+ temps), but can have some bitterness in the Summer.

Best tasting by far (from many we've grown) is an 1800's French heirloom called Merveille des Quatre Saisons (marvel of the four seasons) --- a MUST TRY for all lettuce lovers!

Tony

https://ohioheirloomseeds.com/products/merveille-des-quatre-saisons-lettuce-seeds

stock photo

Check out the Batavians, sometimes known as summer crisps. Varieties such as Nevada, Sierra (and it's descendants), Magenta, Cherokee, Carioca, and a few others. They are my favorites. The leaves have a bit more texture to them, though they are not tough at all. They can take more heat as well.

We don't get hot summers here (sometimes up to the 90s) but I've been able to grow lettuce through the summer with the aid of some shade cloth. That really makes a difference - and it isn't that expensive.

Sorry I don't have any lettuce that will stand triple digits. I have grown Summertime and it does stand up as long as the Romaines. Igloo also is a heat resistant cultivar That is as productive as Summertime.