Latest Leaves Very Yellow, Outside Grow

Hello. I have 12 plants, 6 in pots and six in my garden. It has been raining like crazy in the northeast (Aug 12, 2018 post) and not much sun, was very hot and humid before, now still humid. On three of my garden plants, the new leaves are coming in yellow on the outside in, only the middle rib is green (see pic). White Widow (fem). pH is above 7 and I fertilized with basic 24-8-16 3 days ago. Older leaves remain green. No issues with my tomatoes, etc. pH in potted plants a tad below 7 but they are not having this issue. Plants about 12" - 24" (had issues with the first batch, my fault, so replanted). Iron deficiency is an obvious guess but it happened so quickly that I am not sure.

Thoughts? As always, thank you in advance.

If you are growing in soil, recommended pH is 6.3 to 6.8. See if you can lower it to within that range. At 7+ certain nutes can be locked out and look like deficiencies but she just cannot take them up efficiently

Here u go

As u can see from the chart it resembles a nitrogen deficiency. But from your mention of recent feeding that should not be the issue. Attempt to correct that pH and watch new growth. Those damaged leaves maynot correct themselves. But new growth is our objective. Also do not remove those leaves yet

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Thanks, will do!

Looks like magnesium deficiency. Could be from lock out.

I’d add some cal mag (which usually contains lots of nitrogen as well), ph properly, and if doesn’t clear things up within a week I’d flush with pH 6.5 h2o and try to get that pH into a better range.


Magnesium Deficiency

cannabis-magnesium-deficiency-closeupcannabis-magnesium-deficiency-closeup.jpg1154x866 97.9 KB

Magnesium helps supports healthy veins while keeping a healthy leaf production and its structure. Magnesium is significant for chlorophyll-production and enzyme break downs. Magnesium which must be present in relatively large quantities for the plant to survive, but yet not to much to where it will cause the plant to show a toxicity.

Magnesium is one of the easiest deficiencies to tell… the green veins along with the yellowness of the entire surrounding leave is a dead giveaway, but sometimes that’s not always the case here. In case you have one of those where it doesn’t show the green veins, sometimes leaf tips and edges may discolor and curl upward. The growing tips can turn lime green when the deficiency progresses to the top of the plant. The edges will feel like dry and crispy and usually affects the lower leaves in younger plants, then will affect the middle to upper half when it gets older, but It can also happen on older leaves as well. The deficiency will start at the tip then will take over the entire outer left and right sides of the leaves. The inner part will be yellow and or brownish in color, followed by leaves falling without withering. The tips can also twist and turn as well as curving upwards as if you curl your tongues.

Excessive levels of magnesium in your plants will exhibit a buildup of toxic salts that will kill the leaves and lock out other nutrients like Calcium (Ca). Mg can get locked out by having too much Calcium, Chlorine or ammonium in your soil/water.
One of the worst problems a person can have is a magnesium def caused by a ph lockout. By giving it more magnesium to cure the problem when you are thinking you are doing good, but actually you are doing more harm then good. When the plants can’t take in a nutrient because of the ph being off for that element, the plant will not absorb it but it will be in the soil… therefore causing a buildup. A buildup will be noticed by the outer parts of the plant becoming whitish and or a yellowish color. The tips and part way in on the inner leaves will die and feel like glass. Parts affected by Magnesium deficiency are: space between the veins (Interveinal) of older leaves; may begin around interior perimeter of leaf.

Problems with Magnesium being locked out by PH troubles

Light Acid Soils, soils with excessive potassium, calcium and or phosphorus


Magnesium gets locked out of soil growing at ph levels of 2.0-6.4
Magnesium is absorbed best in soil at a ph level of 6.5-9.1 . (Wouldn’t recommend having a ph of over 7.0 in soil) anything out of the ranges listed will contribute to a Magnesium deficiency.
Hydro and Soil less Mediums

Magnesium gets locked out of Hydro and Soil less Mediums at ph levels of 2.0-5.7
Magnesium is absorbed best in Hydro and Soil less Mediums at ph levels of 5.8-9.1
(Wouldn’t recommend having a ph over 6.5 in hydro and soil less mediums.) Best range for hydro and soil less mediums is 5.0 to 6.0. Anything out of the ranges listed will contribute to a Magnesium deficiency.

Solution to fixing a Magnesium deficiency
Any Chemical/Organic nutrients that have Magnesium in them will fix a Magnesium deficiency. (Only mixing at ½ strength when using chemical nutrients or it will cause nutrient burn!)
Other nutrients that have magnesium in them are: Epsom salts, which is fast absorption. Dolomite lime and or garden lime (same thing just called different) which is slow absorption. Sulfate of Potash, Magnesia which is medium absorption. Worm Castings, which is slow absorption. Crabshell which is slow absorption. Earth Juice Mircoblast, which is fast acting. (a must buy!! Has lots of 2ndary nutrients).
Now if you added to much chemical nutrients and or organics,( which is hard to burn your plants when using organics) You need to Flush the soil with plain water. You need to use 2 times as much water as the size of the pot, for example: If you have a 5 gallon pot and need to flush it, you need to use 10 gallons of water to rinse out the soil good enough to get rid of excessive nutrients.

Wrote by Stitch

Posted by Garrigan62 Moderator


Reposted by: drinkslinger :joy::joy:

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I don’t have the attention span to type that much. :wind_face:

@iramidi, i think your ph is too high and their not getting enough iron. need to keep ph around 6.5 in soil to get the best of all nutrients. ph is usually the problem 9 times out of 10. nitrogen, magnesium, … start at the bottom of plant and work its way up to the top. hope this helps.

So I added a mixture of lime and epsom salts and the plants that had streaky yellowing leaves with green in the middle seem to be slowly improving but this plant that had no problem now has a very yellow middle section. If it is a sulfur deficiency, I thought the epsom salts would resolve that. Any thoughts? again, White widow (fem), outside grow. Thanks.

I would text and correct the soil pH… adding more nutes won’t be beneficial if the pH isn’t in the correct range. Maybe do a soil slurry to test it. Do you have a pH tester or strips? I use pH-fix Macherey-Nagel strips. Works the bomb even in a soil slurry. Good luck!