Dark brown spots leading to necrotised leaves

[D1LDN]

Hi guys,

This is my first grow; I've made lots of rookie errors along the way but have managed to make to Week 8 relatively unscathed until now.

I've got two 12L pots growing outdoors. First one an "Alpujarrena" seems remarkably robust, with no real issues to date.

The second, BCN Critical XXL, has been slightly more temperamental. It had a short bout of powdery mildew that I think is now under control, but over the weekend it's developed small, dark brown dots on the leaves; and now some of those leaves are turning yellow/necrotising. Photos attached.

I'm not sure on my pH, but I do know that I live in a hard-water area:

Calcium carbonate(CaCO3): 280 ppm
Degrees Clarke:20
Degrees German(DH):16
Degrees French:28

Which leads to me to believe that this isn't a CalMag issue despite the fact that whenever I've looked up the leaf symptoms, that looks like the most likely scenario.

Perhaps my biggest error was potting both plants in Miracle Gro compost. I know that's seen as "too hot" in terms of nutrients, so I haven't fed with anything else so far, especially given that Miracle Gro is meant contain up to six months worth of feed.

I've bought some Bio-Buzz Bloom, arriving later this week...

Only other thing to note is that it's growing in a pretty exposed place and it was windy and wet this weekend.

Any advice hugely appreciated - shout if you need more images of the bud(lets) etc (they seem fine enough, maybe a bit on the small side).

 

[Mañ'O'Green]

It does look like calcium deficiency. I cringe whenever a farmer says he does not know his PH. Even with the best nutrients that buffer PH you should still know that it is working. You need a good PH soil probe to check the PH in the root zone. Get a Blue Lab Leap soil probe and meter or an Accurate 8 soil probe or the clone of it. Don't buy cheap ones they just do not work.

Other magnesium in excess can lock out calcium. Did you apply Epsom salt?

Miracle grow has about 30 products which one did you use. Do you have a picture of the guaranteed analysis?

Yes your starting water is too high in calcium which is not helpful. It already exceeds the plant's needs. So we may have several issues at work here.

 

[D1LDN]

Thanks for the quick response - appreciate it.

I've now purchased a pH tester.

No Epsom Salts - I've not applied anything to the plants since planting.

Annoyingly the Miracle Gro compost doesn't have a guaranteed nutrient analysis breakdown beyond the standard marketing blurb:

Shall I follow-up again once I have the pH test?

BIG thanks.

 

[Jackson]

I have learned the hard as I didn’t check ph and my plants looked burnt overnight

 

[D1LDN]

OK, at root level, we're looking at ph 6.5.

The other, healthier plant, is at ph 7.

Both watered with the same tap water.

 

[karlkutta]

are you in soil? should be going in at about 6.2 i think.
i recently noticed a big issue where my run off came out with super high PPM, so i had to adjust that with tons of flushing which wasnt easy. see what your run off is too i guess good luck!

 

[Mañ'O'Green]

In soil you want the PH a little lower 6.3 -6.4. Many charts run as high as 7.0 but you start to lose some metals ~6.4.

 

[D1LDN]

Thanks guys.

They're both in soil - a potential issue being that it's Miracle Gro all purpose compost which is loaded with six months of slow release nutrients.

Is it unusual that the healthier looking plant is doing well at ph 7?

The one with the dark spots and yellowing leaves isn't TOO far off the optimum at ph 6.5...yet seems to be suffering.

Can you suggest any potential causes or remedies, going back to the initial calcium/magnesium deficiency diagnoses?

BIG thanks.

 

[D1LDN]

Just to add..

The rest of my plants - ranging from rocket (arugula for the US crew), radishes, spearmint, thyme, flat leaf parsley, peppermint, chives, rosemary through to various ornamentals and grasses seem to be happy enough with the same compost and tap water.

Granted there's a reason that those are all so much easier to grow, but just wondering whether this is more of a specific nutrient deficiency as opposed to the ph values.

I'm completely new to this so please bear with me if I'm being completely daft or ignorant here!!

 

[D1LDN]

Update: things are getting considerably worse as the day progresses.

Real hot spell here so assuming that the deficiency is meaning that the plant can't cope with the sun and heat.