What state are your plants in to make that determination that it needs a quick shot of Phosphorus? If your fert already includes it throwing more may do more damage than good.

Leaves are turning purple.

How do you know you need a fast phosphorus cure for your plants?

To answer your original question, bonemeal is readily available in the garden section of stores (it will also add calcium though). If you can find it, ground phosphoric rock will also work.

Could you post a pic? Sometimes the sun can cause some purple color to appear on the stem as well as leaves.

@ Otta, Bonemeal and rock phosphate are slow acting, not fast.

@Hab, I can send photos when I get home. Leaves are progressively getting worse as days go on w/ the purple blotching.

Sounds like it may be sunburn, pics will help identify more so will wait until you post. Did they just get put outside?

acdacd

Dude, so like if you're like looking for like a quick hit man, try freebasing some rock phosphate under the leaves.

Ha, I kill me ;-)

Seriously, I agree with habjolokia, better to be sure of the cause before taking action. If they are outside, how recently? It could just be the plants naturally protecting themselves from higher UV. Are they in pots or the ground?

I'll await the pics as well.

First off, Purple is a common and normal color in many peppers. you dont say what kind of plants you have. IMO, if it is a nutrient deficiency, I would guess (with my limited knowledge) that is probably Nitrogen that is deficient if anything. Nitrogen usually greens up foliage. But before you dump some 28-3-2 lawn fertilizer on your plant, be aware that I am not a botanist and too much nitrogen can "burn" your plants.

If your plants are otherwise healthy, i wouldn't worry about it.

If purple leave are a problem, then this Black Cuban is in trouble big time:

Concur: many varieties of pepper have purple coloration in their leaves. Phosphorus is essential for fruit set and development. If the young fruit were dropping off I would then worry. If you do need a fast fix, then a liquid foliar feed like Bloom Booster by Miracle Grow, Blossom Booster by Peters, or Jack's Blossom Booster is the the way to go.

Yes, purple is not a color any pepper I've seen turns because of a nutrient deficiency.

Sometimes there will be some purple veins on the stems / leading to the leaves, maybe even mottled on the leaves.

It can be a nutrient deficiency, or a reaction to the light or genetic. I tend to think nutrient deficiency would be the least likely - particularly since you have fertilizer mixed in.

If they look healthy overall, I wouldn't worry about it.

They have been outside for four weeks, so I highly doubt it is sunburn as this started about a week ago and is getting progressively worse. It also appears on both new and old leaves.

http://i1049.photobucket.com/albums/s400/jdolan29/Leaf/2012-06-05_162657.jpg

Well, that does look pretty scary. I don't think it's sunburn either. Not really sure what it is. Hopefully someone else knows for certain what it is or how to treat it.

It is mainly on the top of the leaves at well. I don't see it on the underside. Possible burn from insecticidal organic soap mix?

When you applied the soap did you rinse it off? I have not used any chemicals or soaps so not sure what they can do to the leaves. I have read many post about rinsing the soap off because the sun and soap on leaves can burn. What i read, best to apply in the evening then let it set overnight and rinse off in the early morning.

I think you just burned your leaves with insecticidal soap. The soaps usually contain potassium salts, which suck the moisture out of things like aphids by osmosis, killing the bugs. Unfortunately, the salts also suck the moisture out of plant leaves, killing them too. Any little divot or low spot in the leaf where the liquid can collect and the salt can concentrate as it dries will suffer damage. I hate insecticidal soaps for that reason, you are better off to use greatly diluted dishwashing liquid to coat the bugs in a soapy layer to suffocate them. Even that can damage the plant tissue, but nowhere near as bad as with insecticidal "soap" (potassium salts).

Agreed. Everytime I've ever used storebought insecticidal "soap" or any horticurtural/essential oil spray's it's burnt my peppers (and other stuff too, but the peppers seem to be most affected). And trust me, I've got crazy jungle bug issues, so I've tried a bunch of stuff. It doesn't seem to matter what I do. I've always been careful to do it in the shade and when it's cool - still, I always get some damage.

I only spray a homemade mix now as my go to bug WMD. 3 parts water to 1 part alcohol with a 2 percent solution of murphy's oil soap (5 tbsp per gallon). I just keep it in the garden sprayer ready to go every evening when I go out on recon. I've never had any burning with that mix, it doesn't need to be rinsed, and it's a good knock down. I also use 2 percent solution of neem, also with murphy's, once per week.

Not only will this stuff not burn your plants, but it will cost you a fraction of what you pay for the overpriced crap that they push in your local garden center.

Don't worry to much about it though, it's just ugly. Your plants will grow out of the damage in a few weeks.

Good luck!

PJ

I have been using something called TKO Phosphite, plants seem to love it. It is 0-26-26 with a near neutral pH. The phosphorous is PO3 instead of PO4 and can be taken by the plant immediately.

This is an odd phenomenon. I just noticed some deep purple on the stem of one of my plants. This particular plant has been slowing in growth lately and is not as bushy as the others. The buds are smallish, but aren't dropping to any alarming degree.

It gets treated like the rest. I am not worried about it because there was another plant that wasn't growing at near the pace of the others. Eventually it changed from a sickly looking plant with yellowing leaves into one of the strongest.

My verdict on all this is that some plants go through differing patterns to maturity. They get sick and then better even though you haven't done anything unusual.

Peppers are weird.

That looks like a Texas black pearl. It's ornamental is normal for its color. I have one here at home. Cold soil will cause defiency. Walmart sells a liquid 15-30-15 fert.
Hope this helps.