Those leaves are failing for whatever reason.

Please post another image, one with newish tip growth isolated against a plain background-- prop something behind it or get someone to hold the background in place.

Thanks for your reply.

Here's the tip of the plant. Note the slight purple hue on the new growth. Does this picture tell you anything?

I've also noticed that the ends of some flower clusters are falling off, dropping maybe 5-10 flowers. Also, some clusters stems farther up the plant are curling up and back toward the main stem. I'm not sure if this even signifies a problem. This just started recently.

This post was edited by robhan on Thu, Jul 17, 14 at 22:45

Looks like severe phosphorous deficiency from the photos so what and how often have you been feeding it?

Dave

Well the soil started out with 3 inches of compost tilled in, then I fertilized with 5-5-5 in May when I transplanted, and fertilized again about two weeks ago, both times following the instructions on the bag.

Is that not enough phosphorous?

Don't get me wrong, I am not saying there isn't some herbicide damage as it is highly likely in the first photo. But the second pic shows definite signs of phos deficiency.

In theory what you have added should be enough IF your soil pH isn't heavily skewed. If it is then any nutrients you add aren't available to the plant. Of IF they haven't been flushed out of the soil by heavy rains or over-watering. Or IF there is an active soil food web in the soil. Of IF they aren't in containers of some type. Lots of "ifs".

Either way it sure won't hurt to give them a quick boost feeding of a liquid phos fertilizer.

The herbicide damage you can't really do anything about except support the plant as much as possible and hope it will recover. And talk to the neighbor.

Dave

If you have been using 5-5-5 all along, probably you have supplied more phosphorus than needed. Plants need 3 times more nitrogen and twice as much potassium than phos.

I would switch to a fertilizer with 3 - 1- 2 ratio, such as MG blue water soluble (24 - 8-12 ), or MG 4pack in green bottles.

Another neighborly advice: Trim, remove any and all yellow and yellowing leave branches. They serve no purpose but instead are burden on the plant and invitation for diseases.

I've not seen phosphorus deficiency here in tomatoes growing in the clay-based soils of the PNW.

I suspect environmental stress and resultant low-functioning roots due, in part, to our recent sustained heat wave. (Really high temps for our region, not so for many other places.)

Take a look at this
"Growing tomatoes in your home garden" from Oregon State University (at link, below)

Here is a link that might be useful: growing tomatoes

I agree that phos deficiency is uncommon most anywhere but its availability to the plants depends on the soil pH. So if the pH is out of whack then you can have all the soil phos in the world and the plants will still show the deficiency symptoms unless you use a liquid/water soluble supplement.

Dave

Thanks everyone for your replies.

I found my soil report, which showed 156 ppm P1, which it says is "very high". This was before I added compost (3 inches, 0.51% phos). pH was 5.2, also before compost. 3 inches of compost (pH 8.0) into 12 inches of soil should yield a pH of 5.8 (if such a thing is calculated by weighted average) - so my pH is low. Could this be my problem? Can I add lime to the soil with the plants already established?

I have read that tomatoes should be fine in pH range like 5.6 to 7.2 but 5.2 would be way too low. I would add fast acting lime. Probably the soil test has also made some recommendation on how to deal with low pH situation. I would shoot for like 6.8 as optimum level for 99% of garden vegetables. But anything from 6.2 and up should be fine in the short run.

OTOH, changing pH takes time and cannot be done overnight. The best time is in the fall , to add lime and let it work.

Could this be my problem?

Definitely. Plus compost isn't going to neutralize soil pH within one season and most compost has a pH of around 7 not 8. 3" of compost will decompose fairly quickly and the soil will return to its native pH.

Dissolving some lime in water to use on the plants may get you through this season but I can't begin to know how much or how often. You'll have to let the plant appearce tell you if it is working or not.

Then this fall consider liming the soil well so it has time to work before next year.

Hope this helps.

Dave