Your soil may not be warm enough. Blossom Drop occurs if the night temperature falls below 55. Heriloom tomatoes also need a little bit of TLC depending on the strain. I would try to use some organic BLoom Boost- Such as Foxfarm BIG BLOOM - I use it on my tomatoes espeically on my herilooms and it really helps the flowers set into tomatoes. Hybirds seem to have less problems with setting of the fruit. ever try them?

The weather more than anything is going to dictate fruit set.

That week of 100+ weather is likely why you got blossom drop instead of fruitset. You may want to shake your plants when they blossom to help aid fertilization, and hope the weather stays moderate. Once you have fruitset, the tomatoes can tolerate more heat.

I'm south of you in Prunedale. Nights here have been 50 or below (even during that warm spell they were below 55) so I'm getting blossom drop too. Around here I have found the nighttime low temps are the biggest barrier to fertilization. Kimberly is my only plant to set fruit so far.

I'm in Santa Clara. Yes I had the same happen to all of my plants too as far as the blossoms dropping. It shouldn't be long now as I'm seeing fruit set as of yesterday.

Damon

There are other contributing factors to blossom drop as well although temps is the main one I think. I linked the FAQ on it for you below if you want to review it.

Dave

Here is a link that might be useful: Forum FAQ's - Blossom Drop

Thanks all. From what you've posted I'm guessing it's the temps. After baking a couple of weeks ago we first had a blast of very strong winds and now an unseasonably cool spell (high 60's in the day, low 50's at night). Hopefully things will moderate soon and I'll start seeing some 'maters. The plants are looking great, just no goodies.

I'm just about 40 miles noth of you in Martinez. Same weater pattern as you. Two of my 8 plants juuuust started started to set a few tom's each. Should be soon for ya!

I have a volunteer that set fruit months ago. The volunteer popped up in a raised planter in front of the side of my garage, where eves and other plants offer some thermal protection at night. Furthermore, the outside wall of the garage there is west-facing, so its gets pumped with heat in the afternoon.

I am suggesting you put a tarp over your flowering plants, somehow to shield the plant from the harsh night air. And exploit a west-facing block wall, or similar, if possible.