Can someone explain PPM

Hello…I’m new to growing and currently on my first grow.
It’s a purple haze autoflower. I tested my water for ph and it was good. The ppm reads 58. Do I need to worry bout that? How do you adjust it?

My one plant has yellow/brownish spots too. Calcium deficiency??

Purple haze autoflower going into week 4. Using fox farm ocean forest in 3gl fabric pots. 73F/58%rh
Using VS1000 Led grow light 24/7

I’ve just been watering up to this point. Ph of soil is btwn 7/8.

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Hi @MommaTT!

In my experience, I only worry about PPMs when I’m growing in a straight Coco grow. The reason is Coco is neutral, unlike soil which has amendments in it to feed the plant.

With Coco you HAVE to add the nutrients or the plants will starve, which is why Parts Per Million (PPM) is measured in this case. It measures input of nutrients (food) and output (excretion of food). It’s how I determine if my plants are eating too much, too little, or if it’s just right. Like the three bears, ha!

I don’t do this with soil because, I shouldn’t have to add soil contains nutrients already and the numbers would be making me stressed because the numbers would be all over the place BECAUSE it’s soil full of food that I might be tempted to wash out.

With Coco, I can always correct if I feed too many nutrients by flushing them out and letting the plants recover, and starting over. With soil, this flushing business would be detrimental.

Long story short, one of the reasons is PPMs are measured to understand nutrient digestion or lack thereof of plants.

I hope that makes sense.


Yes, that makes since. I was stressin over that! Lol
Do you know why my one is yellow/brownish?

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I think she looks beautiful and healthy. It may be because it’s on the bottom and got a little burned from the watering process. You can take it off, I normally do if it’s the only one affected.

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How do you take it off? Do you think it’s ok to add notes now? I’m going into week 4 and have just been using water. Using fox farm ocean soil


Just snip it off with scissors.

I too use Fox Farms Ocean Forest, and find it has plenty of nutes in it for the first month or so of vegging.

Are your plants in their final pots?

I always wait until I transplant into the final containers to start adding nutrients.

Looks like you’re off to a great start :+1:


Yes they are. I have them in 3gal fabric pots


You can start adding nutes.

Since they’re autos, they will begin to flower soon.

Be sure they get the proper nutrients for the flowering stage.

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You’re the best. I didn’t catch the auto part. :v::star_struck:

Glad I didn’t lead you astray @MommaTT . :upside_down_face:

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Thank you guys!!! You’re awesome!


Keep us updated on the progress of your grow!


Will do! Thank you guys


You’re welcome! Looking forward to seeing more! :v::upside_down_face:


The SPOTS you see are usually indicative of a Calcium issue -deficiency

cal/mag is a excellent solution…but as in all things, do not overdo it

  • In soil, calcium is best absorbed by the roots in the 6.2 – 7.0 pH range (in soil, it’s generally recommended to keep the pH between 6.0 – 7.0, but calcium specifically tends to be best absorbed above 6.2)
  • In hydro, calcium is best absorbed by the roots in the 6.2 – 6.5 pH range (in hydro, it’s generally recommended to keep the pH between 5.5 – 6.5, but calcium specifically tends to be best absorbed above 6.2)

Thank you! After doin my research, that’s what I came up with. I did add some cal-mag yesterday so we’ll see how she does. :crossed_fingers:t3::crossed_fingers:t3::slightly_smiling_face:

remember, calcium takes time to go from soil to the plant…the leaves that are showing signs will not repair themselves…trim them off at a later time. New growth (about 7-10 days in_ should be free of telltale sings

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Ok…thanks for telling me. Learning so much on here!!

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Ppm stands for parts for million, it’s a unit of measurement, i have been running autos perpetually for 9 years and the best advice i can give you is if you are useing a med made for cannabis you feed very little i use botanacare pro grow 1 ml per USgal a small splash into a 16oz cup of water stir and feed go light, for blomm Atami Bloombastic same dose same drill but if not careful you will burn them.

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Hello…and thank you for the information. I just did my first feeding a yesterday.

This is what I’m using.

When feeding autoflowers they need 1/4 of recommended dose or less depending on how strong it is, autoflowers are notoriously simple to burn, the only thing i give my autos is botanacare pro grow in veg mode and dont feed seedlings start light at 21 days from sprouts or if plant has 3 nice sets, if your using fox farm dirt feeding is optional all botanacare is is fish mulch and a bit of nitro have never burned a plant in veg, when your plant has topped ie stopped growing vertical and is in full flower ave 50 days or so i flush out any leftover food residue check ph and feed Bloombastic i allso change the spec of my light to full bloom ie red and ir i have a 2 cycle light, i grow my autos under blue light bc full spec has red and ir in it, this can cause an autoflower to flower prematurely think of full spec like the sun they will grow but yield is smaller, you make shure you have good drainage put the bean in a 3gal pot and let it do its thing, if a branch head is smashing against a fan you can leaf tuck or if really bushy you prune to improve airflow and get branches into light, keep things simple dont have huge temp and rh swings i use ac and grow strains that like heat, get shears, Teflon coated fiskars and a jewlers loupe or good glass, keep your ph runoff around 6.2 or as close to that as possible, dont complicate things, use a light food very lightly only, fox farm has ok bloom agent i would go 1ml per USgal after a watering pour a small splash into a 16oz cup of water, stir, give to plant and drain, i use atami bc it enhaces the flower you do have.