Leaf Curl problems - The Claw

Hi all,

Many of our plants are exhibiting serious leaf curl, affecting young and old plants. The leaf curl does not extend to the older light leaves, or those that were healthy before the leaf curl began. Once the leaf curls, it dries from the outer edge and eventually crumbles.

The lighting is 800W - 400HPS + 400MH.

Water pH is tested daily and always within 6.2 - 6.9. Plants are soil based with a mix of potting soil, sphagnum moss and perlite. The potting soil is similar to Miracle Grow potting soil.

Plants that get grow fertilizer, receive it only on watering days. The fertilizer is a hydroponic liquid mix that is used at its lowest if not lower mix ratio, since leaf curl problem. The young plants, such as that in the attached pic, have not been fed, even though they are now in their fifth week. As you can see, once leaf curl happens, growth is severely stunted. New leaves never get big, just curl and burn up. Bud pistols get red prematurely and resin never builds up. We have lost several plants so far.

Since leaf curl has come on, all plants have been water flushed, some more than once. Cal/Mag has been added to grow and bloom fertilizer applications for one week now, in case the plants have experienced lock out, but not sure if the cal mag is working.

From our research, it seems to lead to chemical burn, but we are pretty sure that the young ones were not fertilized, so how could it have affected all? The lights are on a 20 hour regimen, which has been the case during healthier crops, but thought I should mention it anyway, especially if an 18hr cycle would be better.

We have checked around and can't find similiar pics or descriptions. Any help will be greatly appreciated.

 

Thanks for the quick response. More pics are included, one is the baby (Northern Lights) shown earlier, the other is a bit older (bag Sativa), about 8 weeks.

The pH of the water we give it is between 6.2 - 6.9, but that is before adding fert. and Cal/Mag now. We did note that runoff water from one of the flushed plants was 5.5pH. Unfortunately, we don't have any way to pH test the soil. The soil is about 2 parts Miracle Grow soil & Spaghnum Moss, 1 part Scott's potting soil, 1/2 part perlite with earthworm castings on top. We just got a bag of Ocean Forest Potting Soil, an organic mix, that we started to add just to try something new, and cut out 1 part potting soil.

We did re-pot several plants during the last 2 1/2 weeks fearing that the soil was the problem. We switched from smaller pots (6") to 8" and those that were in 8" pots we moved into 12" pots.

The fertilizer we use is Flora Nova 2 part. We water when pots show dryness, about every other to every third day. Overall, about 24 plants are watered with about 1 1/2 gallons of water in a session. The room temp is always around 76F.

 

What do you think could have driven the soil pH so low? And what's the safest way to get the soil pH back in balance? Are there certain soilds that cause pH to drop?

We'll be picking up a soil tester this afternoon, thanks for the heads up.

BTW, we just did a flush on one of our Sativa babies, and it tested out at 5.7 pH.

 

Considering that low pH is causing the leaf curl, what is the best way to get it back up to normal pH levels? Through fertilizing and Cal/Mag? And will the Cal/Mag take care of the lock out problem, and how long will that take?

 

any idea as to how high to take the pH and for how long? haven't read anything on this before.

oh, and thanks

 

Alright, thanks for all the help. We got the pH up and down and will see if we can turn things around. Hopefully will have some nice pics to post soon.

Keep it lit.

 

so far we see a little improvement, and for the most part, new growth is coming on without as much curl as previous. we just started raising the pH yesterday, so we'll just have to see.

 

Is that an acceptable measure for testing the pH fofthe water runoff from the soil as well?