I have no clue where you are, but I doubt night temps in the late spring/early summer are the problem. I say this because even though my heirlooms are in a greenhouse, it is unheated once the night temps are above 40 (even when heated it just keeps it about 40). Rarely are our night time temps above the low 50s.

What particular heirlooms have you tried? What are you doing as far as soil temperature (plastic mulch etc)? We have cold nights here in my Idaho garden, and I've had great success with lots of heirlooms (70+ varieties last year). You should look into some of the Russian varieties (I particularity like Sandul Moldovan and Purple Russian) as they're real cold hardy.

I've tried the Ukrainian black tomatoes including Black Krim, which is an incredibly good tomato. These blossom lavishly, but only set and produce 0-2 tomatoes per bush.

Even Brandywines, which are supposed to be easy to grow, have only produced two or three very poor fruits per bush.

The only heirloom that produced even adequately was a Beefsteak.

I've tried planting the bushes in the worst soil in the yard and this does reduce the size of the bush, but sets no more fruit. After years of failures, the only variable that remains I can think of is the daily temperature variation, which can be extreme and is rarely less than thirty degrees. I know that fruit setting is temperature-dependent and hot days with cold nights must be a problem for most of these heirlooms.

None of the sites I've looked at rate varieties by this criterion, however.

Golodkin,
You might get more specific help and input from people in similar areas if you let people know where you live. Just a friendly suggestion.
There are lots of reasons for tomatoes not setting fruit. Have you had your soil tested? Phosphorous deficiency is one reason. Also overwatering, lack of sunlight, and/or temperatures too high during the day. However, the problem seems unlikely to be temperature-related since you say you live in "the most prolific commercial tomato-growing area of the US."
BTW, Brandywine is definitely not easy to grow. It is very fussy about daytime temperatures, and many people have trouble with them not setting fruit. Something about the stigmas, I think.

Golodkin- I doubt it is the temp. We have similar climate and I grow mostly all heirlooms and although I have fooled around with tomatoes for years, I am hardly an expert. Years ago I grew in the soil but now I grow in 5-15 gallon pots plus earth boxes and did quite well last year. Perhaps you have nemetodes in the soil or some other issue. LInda

According to info I've collected:

= When daytime highs are above 90-95, pollination will fail. However, pollination can still occur in the cooler temps overnight. (Some varieties do better in hot temps, and in general cherries and similar types set fruit better in hot temps. Last year my Juliet set every single blossom -- barring one truss a hornworm ate -- despite 90+ degree daytime highs for most of August.)

= When night-time temps are below 55, pollination will fail.

Someone more knowledgeable will have to address the finer points of temperature situations.

However, unless every single day was too warm last year and every single night was too cold, I think temperature probably isn't the reason for your lack of fruit-set. And I doubt the difference between day and nighttime temps has anything to do with it.

I have a soil test kit I'm waiting to use as soon as the garden dries out from the recent rains and I'm sure it will be informative.

The temperatures here in Sacramento are extreme and in a hot summer can go over 110� in the day and have a nighttime temperature in the low 50�s, which for some varieties can be both too hot AND too cold. Usually it's not quite that bad, usually around a 30�+ spread, say 95/60. The hybrid varieties grown commercially here are developed for these specific conditions...and they grow pretty much as far as the eye can see here (just not in MY garden).

One reason I suspected temperature was that when fruit does set on these bushes, it's always at the bottom of the plants where the leaves are densest and closest to the still-warm soil during the night.

There is no (0) rainfall from spring until autumn and the daytime temperatures and blazing sun usually scalds any fruit not protected by dense foliage.

As I already said, I don't know of any gardener here who has had any success with heirlooms, so I can't ask for advice on what works and how. The local big nursery stocks seedlings for the varieties people hear are great on TV or the net and ask for -- but often aren't suitable for these _local_ conditions, which are unusual.

Some commercial growers here have started growing heirlooms for the local market and have pronounced them "difficult" and doing better in "poorer" soil -- whatever that actually means. I don't know what varieties they use.

Assuming I'm all wrong about the temperatures and it's the soil, SPECIFICALLY what sort of soil problems should I be looking for when I test?

What varieties are most likely to work in these conditions?

golodkin, GW member sautesmom is in Sacramento, grows a lot of tomatoes successfully, and is very knowledgeable.

I went looking for likely threads where she'd posted, and found these; some are better than others, but all might help you on one issue or another:

http://forums.gardenweb.com/forums/load/calif/msg0117572525152.html (and follow the link in her post: many good suggestions there)

http://forums.gardenweb.com/forums/load/tomato/msg062000266779.html (various theories about hot weather and pollination, also other info)

http://forums.gardenweb.com/forums/load/tomato/msg0517195112326.html

http://forums.gardenweb.com/forums/load/calif/msg0816315122993.html

http://forums.gardenweb.com/forums/load/tomato/msg0716384122262.html (general Central Valley thread)

http://forums.gardenweb.com/forums/load/tomato/msg0713553510092.html

http://forums.gardenweb.com/forums/load/tomato/msg0321260316036.html

http://forums.gardenweb.com/forums/load/tomato/msg0204282810466.html

If the fruit that did set were at the bottom of the plant, it might also mean those flowers set fruit during the earliest (and less hot) part of the year. Or that they got more shade than the top part of the plant (and were therefore cooler). Or that they were closer to the soil (and therefore cooler).

The do-it-yourself home soil test kits are worthless. A point often discussed over on the Soil forum here. They give false readings and can easily lead you down the wrong path. A professional soil test is available from the local county extension office for approx. $10-15.

But I have to agree with the others that temps isn't your problem and neither are 'heirlooms'. There is nothing unique about growing heirlooms vs. hybrids. They both have the same needs.

The more likely issues are your soil as mentioned, you planting time (as in planting too late), and your feeding and watering regimen. All would affect hybrids just as readily as they do heirlooms.

Hope this year turns out better for you but if you elect to switch to hybrids there's nothing wrong with that either. There are many great hybrids available.

Dave

Thanks for the links, I'll check them out.

I searched around and found a link to the local garden columnist in the newspaper. Turns out that people here _do_ have a lot of trouble with heirlooms setting fruit when, like me, hybrids do fine for them. The main problems (she says) were the weather and soil chemistry, for which she recommended "Super Bloom" (rather pricey!) to encourage blossom setting. This assumes adequate pollinators, and there are plenty of bees at work here already.

Good advice? Bad advice? We'll see.

This assumes adequate pollinators, and there are plenty of bees at work here already.

Tomatoes don't need bees to set fruit; they are self-pollinating. They just need wind or a good shake to pollinate.

OP wrote "The main problems (she says) were the weather and soil chemistry, for which she recommended "Super Bloom" (rather pricey!) to encourage blossom setting. "

Shows she doesn't understand about plants. Super Bloom won't help.

Contact your county's Extension Service Office as you're likely to receive accurate info there. To locate your county's office, use this interactive map
http://www.csrees.usda.gov/Extension/

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

YUmTomatoes has a good idea about the pollination!

I was having a heck of a time a few years ago with zucchini plants that were only producing aborted squashes. I found out online how to pollinate them myself and it worked like a charm. Every female flower produced a full size squash that I dusted with a male flower:) See if you can find a article or youtube video and how to help them pollinate. I bet you'd use some kind of a soft make-up brush.

Every female flower produced a full size squash that I dusted with a male flower

I've done the squash thing ... with squash.

Unlike squash, melons, cukes, and gourds, tomato flowers contain both female and male parts. As yumtomatoes said, Tomatoes don't need bees to set fruit; they are self-pollinating. They just need wind or a good shake to pollinate. If you want to go high-tech, you can hold an electric toothbrush against the the stem for a few seconds.

For anyone who wants to be really thorough, here's how to pollinate tomatoes (particularly if crossing two varieties):

http://www.kdcomm.net/~tomato/Tomato/xingtom.html

http://www.avrdc.org/LC/tomato/hybrid/02contents.html

I used to live in Sacramento. There is a reason it's called "Sacatomatoes" as they grow like crazy there which was my experience. I grew a variety of different heirlooms & OP varieties with a very few hybrids and always had an extreme glut of 'maters. I did grow in homemade earthboxes after the first year as it was difficult to keep them watered consistantly in the extreme heat if planted in the ground.
Like has been said, tomatoes are self-pollinating - there are no male or female flowers. Each flower contains both anther & stigma. All they need is a gentle breeze to pollinate.
Some of the heirloom/OP I grew in Sac were Black Cherry, Arkansas Traveler, Jumbo Jim Orange (sautesmom I *believe* won a Tomatofest contest with this one), Cherokee Purple, Kellog's Breakfast, Black Krim, Black from Tula, several different Brandywines, etc. They all set amazing amounts of fruit.
I'd find sneaky volunteers in the back of the yard that had fruit.

I'm now in the midwest and WISH I still had the temperatures of Sac to grow in.
I would definitely get your soil tested. It's not the temperatures.

Are you purchasing your plants from Capital Nursery? If so, I recommend that you stop. I did nothing but fight disease from their stock.

I know it's tempting, but don't plant out until April 1. It seems warm enough to plant sooner, but it really isn't. Planting any sooner causes the plants to stunt. As a matter of fact, I was just at Green Acres Nursery this week and they were throwing out their entire Tomato Plant stock because it had frost damage. We most certainly DO get frost this late in the season, no matter what the farmer's almanac says! :)

If the plant stunts, it won't put on its blossoms at the right time, which is during spring. Our summers are too hot for most any tomato to produce. So, you want to plant out at the right time.

One other thing, for the past couple of years, we had very strange weather. We went from rainy season, straight to extremely hot, with very little "spring." Most everyone I know had trouble with their gardens due to this erratic climate.

I've seen no better result with hybrids as I have seen with tried and true heirlooms. I really believe the secret lies in the condition of your soil, the proper light exposure, and planting at the right time. Is there plenty of organic matter in your soil? Most of Sacramento is known for heavy clay soil unless you're closer to the river, then you have a siltier soil. Nothing grows to its full potential in this soil unless it's heavily amended. Once it is though, watch out because it's great stuff.

Varieties that have worked exceptionally well for me:
green zebra
brandywine
black krim
watermelon
san marzano