Strange that the same thing happened to my seedlings tonight. Today was their first day of any outdoor sun, and they were exposed to high 60's direct sun for a little over 30 minutes. Too cold? Too much sun? My seedlings also have purple undersides, but are otherwise doing very well.

Both of your seedlings seem fine to me. Purple is common on the underside of seedlings. Just keep doing what you're doing. As long as they are sturdy you're ok.

Strange that the same thing happened to my seedlings tonight. Today was their first day of any outdoor sun, and they were exposed to high 60's direct sun for a little over 30 minutes. Too cold? Too much sun? My seedlings also have purple undersides, but are otherwise doing very well.

Tomato plants can be very amusing.

Yes, leaves can point straight up, or turn upside down, or curl around and will do that until they get the message that they should behave, and they eventually do. ( smile)

Nothing to worry about unless you see other symptoms that might indicate diseases, usually foliage diseases.

As to the leaves and stems being purple, that too is common , especially when first set out, but when the night and day temps are OK for them that too disappears. And there are several threads about the purple, as I recall, here on this first page.

Hope that helps,

Carolyn

The purple is from a phosphorus deficiency. Seedlings can suffer from seed starting mix that is too acidic which causes poor phosphorus uptake. Peat moss, which makes up a large part of most of starting mixes, has a ph of around 3.4 - 4.0. Most seed mix companies add lime to their mixes to balance the ph, but problems can arise because the begining ph of peat mosses can vary depending on where it was harvested and what species of peat it was. And the PH of starting mix can change over time as more and more water is run through the mix. Phosporus uptake problems can begin at a ph below 6 and uptake is almost nonexistent at a ph of 4 and below.

I solved the problem with my plants by adding just a little hydrated lime to their water once or twice, along with a very dilute fertilizer. The amount of lime I added was about an eighth of a teaspoon per two quarts of water. The purple started to fade after the first application and continued to disappear over the next few days to a week. If you take my approach, you should take it slow and cautious because hydraded lime has a ph of about 12 in solution so it can be overdone. The problem is that you won't know what the ph of your starting mix is but you will know that it is probably below 6 if your leaves are purple. In small amounts lime will balance out the PH so that the plants can take up nutrients. Also be very carful of adding fertilizers. I add mine at about 1/4 of the amount the bottle says to add. So for example my brand says 7-8 drops per quart, and I add about 4 drops per two quarts. And I only add them occasionally after the plants obtain their first true leaves. In any case, the purple problem will disappear fast after they are in the ground, and in most cases they will be fine until you get them there.

Kevin

As Carolyn said above the purpling is common and normal. It poses no threats to the plants and they recover just fine all on their own without any intervention. It isn't lack, a deficiency of phosphorus as testing shows sufficient phos in the tissues and in most all potting mixes. Rather it is a temporary uptake issue due to the plants young age and under-developed root system.

Try to fix it if you wish but often trying to "fix" something that isn't a problem anyway only creates more problems. Alkaline soil pH can interfere with uptake of ALL the nutrients.

Dave