Last year I tried a few new things and although we had a mild summer, no 100 degree days, my plants never seemed to know what the above ground temp was.

Of course, I need 100 degree days to test this but here's what I did:

I started my plants super early - way too early (mid Jan) so they were quite tall. These I planted deeply. The plants were at least a foot tall and I planted so just the top few leaves were above ground. The leaves below ground were snipped off.

One plant was about 3' tall and this one I trenched and planted deeply.

I had two rows of tomatoes and between the rows, I layed black plastic. Around the stems, I mulched heavily with straw. Each time I mowed, I collected some of the clippings and tossed the grass on the straw.

I use a dripline system to water and it seemed like I rarely needed to water. The mulch helped to retain a great deal of water.

In the past, my plants would stop, or slow, producing when the heat set in, but in 2009, the plants were not fazed by the temps.

My best producers last year were of course the cherries but also Nyagous, Amazon Chocolate, Giant Belgium, Earl's Faux, Jersey Giant and Paul Robeson.

The only plants I know that produce when its over 100 are those in my dreams. :-) Seriously, reading here and elsewhere, I've seen that pollination won't happen when it is too hot and/or too humid. The plant can survive it and bring to a delicious finish whatever has set, but I wouldn't expect much, if anything, to start under those conditions. Now, if you are lucky enough to have very low humidity and night temperatures that drop to say 70, you may have some options, and if that's you, you might search for the Arizona tomato growers methods/selections. In Dallas, once its hot, it stays hot, night and day and the humidity ranges from high to stifling. So for us, we have to plant out early and get the most fruit set possible and enjoy while they last.

One last thought, sun shade cloth, 50% sun block, lowers the temp. in the shaded area by several degrees. Using it has extended the time period I'm able to get fruit set.

I had Roma and Matt's Wild Cherry growing in Phoenix ... they did fine with setting fruit until the temps got over 105 and stayed there.

1 - They were heavily mulched.
2 - They got afternoon shade.

We have very active native bees that are "buzz pollinators" that may compensate for the inability of the fruits to self-pollinate at higher temperatures.

It must be spring! Our first question about hot weather varieties.

The myth of "tomatoes won't produce about 90 degrees" comes up yearly, and has been discussed often. I believe it's more of a factor of humidity and variety than heat. Now those of you east of the Rockies may believe that heat and humidity are the same thing, but they are not. I get tomatoes all summer long from several of my varieties, but although we get temps above 105 in summer, we do not have the humidity.

Below is last year's discussion, with recommended varieties to try in blazing temps.

Carla in Sac

Here is a link that might be useful: Hot weather tomatoes

My mom grew tomatoes in Hemet near Paln Springs in the Calif desert for years - there are a few varieties that do set fruit at higher temps but she covered with green nursey shade and misted - they were fine -
There are a couple of keys and that is try to plant your plants so blossums are present before the heat and set tomatoes and plant later group so the "real" heat is past when blossums are ready to set - also sometimes a plant would shut down for awhile but start setting fruit when the temps were correct again
Dennis

Gardeners avoid high temps in a number of ways, one of which is changing the planting date.

Call your Univ of CA Extension Service office in your county. They have Master Gardeners who can help you avoid problems with reliable planting info and likely names of suitable tomatoes.

To find that info, use this clickable map to locate your county's Extension Service office.
http://www.csrees.usda.gov/Extension/

Here is a link that might be useful: click to locate your county's university Extension Service office

While I can't say about California, but here in SE Texas we get HEAT in the summer. It literally burns the plants until they shrivel up.

From experience getting them to set fruit is only part of your battle. After the plants set fruit if the plant is under stress it will make the fruit odd shaped and the fruit will taste very weird.

That being said I have many varieties I am growing this year but one that I may try next year is sold at Tomato Growers dot com... its called the Homestead 24F.

It looks and sounds right, I am not sure about taste...but for sure you can't screw up and tomato any worse than what you buy in the store. When you are at rock bottom there is no where else to go but up.

I grew some of my plants on the east wall of a big barn. They got full morning sun but were shaded from maybe 3pm on. Those plants out produced the others out in the open by 2 to 1.

I would also recommend using shade cloth.

All of those things combined will help you have success when the weather is really hot.

Some Thoughts:

==Plant them in partly shade, if possible.
==Mulch them real good, to prevent soil from getting too warm.
==Water them very late at night or very early morning, sprayin the ground aound the stem.(This is just during scorching temperatures, not all thetime)
==Keep the plant size smaller, so the roots can cope providing water and nutrients.

==Plant them closely, such that the tops shade the ground.

Sunmaster worked well for me here in Texas. They set fruit through July. Then picked up again in September.

cc4digital

While I normally would not link to a Google search, this one ("heat tolerant tomatoes") has quite a number of interesting sites at the beginning of the list. It appears that many Southern state universities are researching this very question to help growers in their areas.

This information, coupled with those varieties that GW growers have found thrive in hot conditions might give you a leg up!

Here is a link that might be useful: Google Search -- Heat tolerant tomatoes

Love this annual thread. I have no reason to doubt what Carla reports from Sacramento. Days there can be scorching hot in summer. However, night temps in Sacramento are considerably cooler than in the CA and AZ deserts, and often are 70 or below. I think this might help explain her success with more heat tolerant tomato varieties. ALL of my varieties shut down production by mid July. I did get some summer pollination on two determinate plants (ostensibly from bees swarming nearby basil bushes), but the fruit were small, tough and dry. I'd probably have a better success rate with shade cloth (e.g. Aluminet 40%), but shade cloth can't help you when nighttime temps are consistently 85/90+ degrees.

I think it has been stated here that your best option is to plant early (mine went out on February 5) in order to have a full fruit set by May. You can and should plant more densely so all the foliage will create a somewhat cooler environment. Enjoy your harvest and accept that you probably won't have much more until October. After my 2010 late spring/early summer harvest, I'll cut my plants back to 2' or less. I'll try to keep them alive/regrow them through the summer heat so they'll be flowering by early October.

If you have the time, space and finances to install and run a misting system, things might turn out better. I'd like to hear from you if you do it.

Varieties? Plant out whatever you want, in my opinion. If you are in a CA or AZ desert, the production shut down is inevitable, plus or minus two weeks or so.

Oh, and forget what you might read here and there about an extremely desert-friendly, heat tolerant hybrid known as "Hawaiian Tropic." It didn't do any better than anything else, and the tomatoes tasted like winter-store-bought anyway.

I didn't have anything really shut down last year. We get teps of about 100-105 on and off for about 3-4 months out of the year here. I had a lot of bee activity and did shake and flick the blossoms to move the pollen around. I got a lot of blossom drop early on on the cherokee purple plants, but everything else continued to set fruit. There was less fruit, but still enough for our family from about 9 plants.

Oh yes, the desert is a whole 'nother kettle of fish! Maybe we should change the mantra to "tomatoes stop producing when NIGHTTIME temps stay above 90" instead of "tomatoes won't set fruit when temps hit 90". I have many times driven to my grandfather's house in the Coachella Valley in July, and when I arrive at midnight it's still 94 degrees. Few if any tomatoes will produce then! But the original poster is from Riverside, and I think the nights cool down enough there to keep getting tomatoes in July.

And again, if you are looking for the VARIETY list of the best heat tomatoes, click on my above link.

Carla in Sac

cc4digital, send me an e-mail. I have a little known open pollinated variety that you should try. Only can spare a few seeds but would love to know if it produces in your situation. It is supposed to.

heres what i do and i get good results / plant where u get morning sun and late afternoon or evening shade / the morning sun drys up the dew and the evening shade helps to keep them from burning up / and mulch good / i set fruit all summer and well into the fall / i do my peppers this way too

I am also in SoCal. After a 2-month tomato shutdown last summer, I did a lot of research to find some tomatoes that might keep going through the hottest weather. I have no personal experience with these yet, but this is the list I made of varieties that are purportedly heat tolerant that I want to try.

Arkansas Traveler
Hazelfield Farm
Illinois Beauty
Pearson
Sioux

I have no idea what I am talking about, so take with big ol' grains of salt and feel free to correct me.

Siletz, Legend, Oregon spring are parthenocarpic. No pollinization required for fruit set.
Designed for cool weather growers. Maybe it will work for warm weather too. I'd love to find out.

Generally speaking, people have a low to medium opinion of the taste of these earlies. My parents loved them.
Maybe they just taste better under PNW conditions.

The legends they grew were massively productive for their size.

Elskunkito:
You may have no idea what you are talking about, but I completely agree with your theory! My experience is that the earlies as a group also do really well in the heat, and they set all summer long. However, I found Siletz and Oregon Spring to be kinda blech. (Legend I haven't grown) Much better-tasting earlies for the heat are Jetsetter, Stupice, Kimberly and Early Swedish IPB.

And Queen, I have never heard of Hazelfield Farm or
Illinois Beauty--where are you getting them from? And I have tried both Sioux and Super Sioux, and was very disappointed with their taste. Traveler, however, is excellent, and Burgundy Traveler is even better.

Carla in Sac

i also live int he inland empire and have found a great techniqe to keeping my plants producing in the heat. first you have to plant the tomatoes where they'll get about 6 hours of sun each day and i have found that the grow stronger when you start them from seeds in seedling starter greenhouses after there big enough to be planted in the garden they should be planted so only the top leaves are showing then to ensure that they get deep root watering use a powered drill to puncture a liter bottle and insert it into the ground next to the tomato plant and it will produce heavily

i have also found that this works best with beefsteak, beefmaster, celeberty, and solar flare

I think one of the ways (as mentioned before) is to start/plant out as early as possible. By " Early as Possible" I mean as soon as the danger of last frost is gone. Now the night lows can drop to as low as 35F. That is fine. Tomatoes can take it.

So this way before the high heat hits your tomatoes have plenty of fruits set. The problem with high heat and humidity it that pollination won't take. So you try to beat that by real early planting.

Sey

Part of the desert zones don't really have frost. I've never seen frost in my garden.

There's no solution for summer production for the low deserts. There just isn't and you're lucky if any plants survive it, regardless of what strategies are used. There's 2 good growing seasons a year, no need to be greedy for a third!

Native Seeds/UofA recommends "Floradade," "Flamenco" and a few others for cultivation. I've found that for low desert purposes, if you accept the summer as the "winter" and grow Sept to May, it seems to work out best and variety doesn't seem to matter, neither does planting depth.

Super Sioux didn't taste great, but good producer, although I planted it in the winter, it's supposed to do better in heat and dry.

Try Florida 91, which is said to be high heat resistant.

I really wish that they'd be more specific about what "heat and dry" means.

In my hot "mountain" (hill) neighborhood nearly everyone has good luck with Black Krim, Mortgage Lifter, Sungold and Sweet 100. I actually leave my plants in over the winter -- my best tomatoes here are from January-April. Then I plant the new ones in Feb or March for the following year while I harvest from last year's plants.

That said, I'd like to have summer tomatoes... so... I bought a couple dozen of the heirloom tomatoes today at Green Arrow (L.A.) that laurel of http://www.heirloomtomatoplants.com/ said were tolerant at 95 degrees, or above. I had to go through and look for the little multiple sunshine icons on her site -- it's remarkable that she doesn't have a heat-tolerant page since she sorts them by every other characteristic. Here are some, from her site:

• "Does well in hight Altitude" - Azoychka, black cherry, black plum, carmello, fireworks, indigo blue berries, jutland, lime green salad, northern lights, sunset's red horizon, Santiago, sweet baby girl
• Sets fruit above 95, maybe to 98 - 1984, black-plum, cherokee-purple, cuostrolee, Florida91, Jutland, purple-haze-homegrown, Santiago, Sungold, Super-Souix, Sweet-baby-girl. Others.
• Sets fruit to 95: berkely tie dye, Black-Krim, black-plum, black-tazmanian, cherokee-chocolate, cherokee-purple, chocolate-amazon, chocolate-stripes, indigo blue berries, japanese-chocolate-truffle, southern-nights, mortgage-lifter. There are others if you look at her site, but I was looking for blacks and purples...

I'm looking around for some of the specific "heat set" tomatoes thatwere developed specifically so they don't drop their blossoms above 95 -- so far this year I found "Hawaiian Tropic" at Armstrong. I'd REALLY like to find a Florida91 or a Santiago. I'm not sure how "high altitude" affects tomatoes, but I am on an Los Angeles "hilltop."

My extension service says that a humidity of 70% is "optimal" for tomato fertilization and production. If it's too high, it interferes with the pollen transfer. The pollen gets too sticky. If it's too low, I think the fruit starts to wrinkle, and the plant is stressed by having to pump too much water.

I think potential confusion about maximum temperature is related to humidity. That is, if the humidity is high, it NEVER cools off, and pollination can't take place. If the humidity is low, the temperature may be fiercely hot in the daytime, but it can cool efficiently at night. That's when pollination can take place. In my high summer, temperatures will be 100F in the daytime, and stay over 80F overnight (and the humidity tops out in the high 90s as well then) and that just shuts them down entirely.

Ideal fruit set temperature is 60-70F with decent humidity.

That is really interesting about the humidity. It's not humid here. It would be interesting to chart it to see which tomatoes stop setting fruit at which temp where it's not humid vs where it is.

Here in Kansas, I grow FL 91 during the hottest part of the summer. They produce 10-12 oz or larger big red tomatoes.

How about planting some "parthenocarpic" varieties. They can set fruits even without being pollinated. I can name one: LEGEND. It can also set fruit in cold weather.

sey

None produced more through extreme heat than yellow pear here. They kept on setting fruit when the others died from the heat.

I live in Arizona and have had success with Early Girls. This year I bought two new varieties and, in doing research, it seems they are both rated well to very well for high heat. The first is Cherokee Purple - got it at my local garden center. Most sites said it would do well in temperatures over 95 and that the fruit is large and sweet. The other is Hawaiian Tropic, which is a hybrid said to grow well and continue to product fruit over 100 degrees. It is one of a number of "heat set" tomatoes, specifically cultivated for high temperatures. I'll let you know how they do.