Tag Archives: nutrients

Question About pH

I read somewhere that I must have the pH for my clients at 6.5.  How important is it to keep it at EXACTLY 6.5?

— Mark in Seattle

Hi Mark,

As long as your pH doesn’t drop below 5.5 or go above 7.0, you should be okay.  The pH always fluctuates, especially when you water/fertilize your plants.

As the plants uptake the nutrients, the pH goes in one direction and when you add nutrients, the pH goes in the other direction.


Dr. Grow

Fertilizing AutoFlowers

In your book, Growing AutoFlowers second edition, you recommend that I start fertilizing with a 20-20-20 fertilizer and only use one fourth of the recommended dose.  Can I just use a 5-5-5 fertilizer instead?

— Duke in Idaho

Hello Duke.,

Thank you for your question. I’m sure this is a question people have as well.

Even though applying basic math makes it seem like using a 1/4 dose of 20-20-20 is equivalent to a 5-5-5, it is not true.  The fertilizer is still a 20-20-20 concentration, but you are using less of it.  When in doubt, it is better to UNDER fertilize AutoFlowers, rather than over fertilize.  You can always add a little more if needed, but it is hard to correct an over fertilizing problem.

If you decide to get a 5-5-5, you should still only use one quarter of the dose recommended on the packaging.


Dr. Grow

Simple Fertilizer?

I’ve been reading your Growing AutoFlowers book.  You recommend mixing fertilizers from several bottles to get the exact nutrient mix.  Can’t I just use a food for veg and a food for bloom in lieu of buying and mixing from 5 bottles?


Hi David,

You can be flexible about nutrients, but must be careful not to over fertilize.

Yes, in theory you could just buy one bottle of nutrients for veg and one bottle of nutrients for flowering.  Remember, only use 1/4 of the amount recommended on the bottles.

The real trick is knowing when to switch over with your AutoFlower plants.  With regular Indica and Sativa plants, you have to force them into flowering by reducing the amount of light they receive down to 12 hours a day.  When you do this, you are choosing when the plants switch into flowering mode.  Therefore it is easy for you know when to switch fertilizers.

With AutoFlowers however, you never change the amount of light and they start flowering whenever they are ready.  You are not telling them when to flower.  Therefore, you will have to watch your plants closely to see when they are showing signs of beginning to flower.  You can switch over to the flowering nutrients when your classes are starting to show the first signs of flowering.


Dr. Grow