What causes these purple leaves -- Sunburn?

Greatgardens · August 7, 2021

I have seen this many times, but it is much more prevalent this season. Is it sunburn? Or something else, like a nutrient deficiency? It is different than the purple on the back sides of the leaves that I see early in the season. Since my sunscald is worse than normal this summer, I thought that it may be a related issue. (?)

Salsacharley · August 7, 2021

Could be magnesium deficiency.

bower · August 7, 2021

I believe it may be a type of mildew or other fungal disease associated with hot and humid weather. We never see it here unless in those weather conditions. Look at the underside of the leaves. If you see some fuzzy growth, then you have your answer.

MissS · August 7, 2021

It's magnesium deficiency. This is very easy to cure with a little Epsom salts.

biscuitridge · August 8, 2021

It's not magnesium deficiency, but I don't know what it is.

Fusion_power · August 8, 2021

It is probably a temperature related nutrient deficiency. While a bit late to try to treat, I recommend getting a complete micronutrient fertilizer and applying liberally. What has your weather been like this year? Cooler than normal spring?

Also, nutrient deficiencies can be caused by nutrient imbalance. For example, over fertilizing with nitrogen tends to inhibit uptake of potassium. Have you by chance heavily fertilized these plants?

Greatgardens · August 8, 2021

Thanks for the replies! My main plant food is Jobes Organic Tomato and Vegetable fertilizer, 2-5-3. I add a good cupful, mixed in the EarthBox media at planting time, along with about 1/2 cup of Dolomite. After heavy fruiting begins, I add 1 tsp of Miracle-Gro Tomato food down the hole every week-10 days. Weather here was cool/rainy in May then turned hot (low 90's) mid-June, then a little cooler at the end of July into August. This summer seems pretty normal to me. Nothing on the backs of the leaves to indicate mildew.

zipcode · August 9, 2021

That is quite unusual. My thoughts were either some beginning of some virus, or a nutrient disorder, although it doesn't really resemble any deficiency I know, maybe a toxicity of kinds. The nutrients commonly associated with anthocyanin accumulations are P and B, but it shouldn't really be any of those.
In case of possible nutrient problems that I can't identify, this is what I do: water heavily with lightly fertilized water with corrected pH (~6). I mean a complete chemical fertilizer, like Haifa, etc. Water so a few liters go the other way.

slugworth · August 9, 2021

store bought plant recently has the same symptoms.
weather/soil related since the plant was root bound and hungry when I got it.
Jungle weather here the past months.

August 7, 2021	#4
MissS Tomatovillian™ Join Date: Dec 2010 Location: Pewaukee, Wisconsin Posts: 3,150	It's magnesium deficiency. This is very easy to cure with a little Epsom salts. __________________ ~ Patti ~

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August 7, 2021	#2
Salsacharley Tomatovillian™ Join Date: May 2013 Location: New Mexico Posts: 2,052	Could be magnesium deficiency.

August 7, 2021	#3
bower Tomatovillian™ Join Date: Feb 2012 Location: Newfoundland, Canada Posts: 6,794	I believe it may be a type of mildew or other fungal disease associated with hot and humid weather. We never see it here unless in those weather conditions. Look at the underside of the leaves. If you see some fuzzy growth, then you have your answer.

August 8, 2021	#5
biscuitridge Tomatovillian™ Join Date: Jan 2014 Location: washington Posts: 499	It's not magnesium deficiency, but I don't know what it is.

August 8, 2021	#6
Fusion_power Tomatovillian™ Join Date: Feb 2006 Location: Alabama Posts: 2,250	It is probably a temperature related nutrient deficiency. While a bit late to try to treat, I recommend getting a complete micronutrient fertilizer and applying liberally. What has your weather been like this year? Cooler than normal spring? Also, nutrient deficiencies can be caused by nutrient imbalance. For example, over fertilizing with nitrogen tends to inhibit uptake of potassium. Have you by chance heavily fertilized these plants?

August 8, 2021	#7
Greatgardens Tomatovillian™ Join Date: Feb 2010 Location: Indiana Posts: 1,124	Thanks for the replies! My main plant food is Jobes Organic Tomato and Vegetable fertilizer, 2-5-3. I add a good cupful, mixed in the EarthBox media at planting time, along with about 1/2 cup of Dolomite. After heavy fruiting begins, I add 1 tsp of Miracle-Gro Tomato food down the hole every week-10 days. Weather here was cool/rainy in May then turned hot (low 90's) mid-June, then a little cooler at the end of July into August. This summer seems pretty normal to me. Nothing on the backs of the leaves to indicate mildew.

August 9, 2021	#8
zipcode Tomatovillian™ Join Date: Jun 2010 Location: Romania/Germany , z 4-6 Posts: 1,582	That is quite unusual. My thoughts were either some beginning of some virus, or a nutrient disorder, although it doesn't really resemble any deficiency I know, maybe a toxicity of kinds. The nutrients commonly associated with anthocyanin accumulations are P and B, but it shouldn't really be any of those. In case of possible nutrient problems that I can't identify, this is what I do: water heavily with lightly fertilized water with corrected pH (~6). I mean a complete chemical fertilizer, like Haifa, etc. Water so a few liters go the other way.

August 9, 2021	#9
slugworth Tomatovillian™ Join Date: Oct 2014 Location: connecticut,usa Posts: 1,152	store bought plant recently has the same symptoms. weather/soil related since the plant was root bound and hungry when I got it. Jungle weather here the past months.