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Nutrients for autoflowering cannabis

Date 12th Sep 2011   Comments 19 Comments »


All autoflowering cannabis plants like any other living things need food to stay alive and grow. But unlike animals or humans plants use nutrients for this matter. Automatic Cannabis plants use large quantities of Nitrogen (N), Phosphorus (P) and Potassium (K) but that is not the end of it because cannabis also needs some “secondary” elements like Magnesium (Mg), Calcium (Ca) and Sulfur (S) but they are used in much smaller amounts than the first three elements. There are also some trace elements that ruderalis plants require to grow to it’s full potential and they are: Copper (Cu) , Boron (B) , Zinc (Zn) , Chlorine (Cl), Iron (Fe) , Manganese (Mn) and Molybdenum (Mo). These trace elements are required in very small amounts and they usually are mixed in the fertilizer or pre-maid soil.
Autoflowering cannabis plants use large amounts of nutrients and you need to supply the plant with all the necessary “foods”. If you use a pre-made potting soil then usually it has a mixed in nutrients that will be more than enough to nurture your autoflower plant for the first two to three weeks of its growth.

Nutrients in soil

Usually premium soils have all the necessary nutrients and especially large amount of Nitrogen because it promotes healthy, fast growth. Pre-made potting soil has enough “food” to supply your auto seedling for the first 3 to 4 weeks but the amount of time the plant can grow without additional nutrients can be very different from strain to strain. Usually autoflowering cannabis plants show signs of nutrient deficiency when they have ran out of “food” and this is the time when you need to add additional nutrients. If you are growing very fast growing autoflowering seeds that can be done in two months of growth then the premium soil is almost able to supply your auto plant with the necessary amounts of nutrients and you will probably need to feed them once or twice. This statement is only true if you use large pot and small growing auto seeds, because small pot contains less soil and less nutrients so you can imagine that the plant will use it a lot faster.
If you use regular soilless-mix or ordinary soil without any added nutrients you will need to add these necessary elements yourself while the plants is growing.

Best fertilizer for autoflowers

Fertilizer basically is the concentrated cannabis “food” and it is calculated in the ratios of N – P – K elements.  Nitrogen (N), Phosphorus (P) and Potassium (K) are the main elements that allow your ruderalis plant to grow and produce leaves, stems, roots , flowers and without these elements your plant will die. The N-P-K ratio is usually displayed at the front of your fertilizer package and it can be something like 10-5-5. These numbers mean that this fertilizer has 10 % Nitrogen, 5 % Phosphorus and 4% Potassium. The remaining 80 % consists of the secondary elements, trace elements and solution where all these elements are dissolved.
Autoflwoering cannabis are very delicate plants that require lesser amount of food than ordinary cannabis strains. This property of autoflower plants can be a big advantage for new growers because you don’t need to worry so much about the feeding of the plants and they can survive much harsher extremes. When you want to feed your cannabis plants with fertilizer you must always read the labels of the packaging and never give plants more than it is recommended by the specific company. Automatically flowering plants are basically a ruderalis cross breaded with other strains and the ruderalis gene is very strong in the plant. In nature cannabis ruderalis plants require very low amount of nutrients to survive and that is why you need to give your autoflower plants small amounts of nutrients and never over feed them. When you start feeding your plants with fertilizer you need to give ¼ or maybe even 1/8 of the required dose and let the plant adapt to these chemicals and when you see that everything is OK you can slowly increase the dose but be aware that it is not recommended that you go further than ½ of the dose that the manufacturer says. Fertilizers usually need to be dissolved in water and you give your plants their “food” by simply watering them. Usually a good practice is to water your autos with fertilizer every other watering. You can also water two times with pure water and every third one give nutrients and the possibilities are endless, so you need to experiment and see what works best for you and your own or purchased autoflower seeds.

Nutrients for Seedling phase

First two weeks of cannabis growth are the most crucial because the little seedling is establishing its root system and it is very fragile. At this stage you must be very careful not to overfeed those little sprouts.  You can start your autoflower off with 1/8 of the required nutes or just give the plant plain water for those first couple of weeks. If you overfeed your cannabis plant at this stage of its growth it is highly possible that the baby plant won’t survive or if it manages to somehow survive then the overall yield of the damaged autoflower cannabis plant will be greatly diminished.
If you are using pre-made potting soil with added nutrients then you don’t need to feed those little auto plant for the first two to three weeks so you can relax and forget about those nutrients at this stage of its growth.

Nutrients for Pre-flowering

Regular cannabis plants have a vegetative growth stage but autoflower cannabis plants usually goes from seedling phase straight to flowering so there isn’t a distinct vegetative growth period. Some growers do believe that the time when the little sprout gets its true set of leafs till it starts flowering is the vegetative growth stage but anyway it doesn’t matter how we call this stage because we need to feed it just like a regular cannabis plant in its vegetative stage. When we see that the autoflower plant starts really fast growth we need to start giving it little more nutrients. Usually it is best to give ½ of the recommended dose of nutes, but if the plant gets really bushy you can give it a full dose. At the vegetative stage cannabis needs lot of Nitrogen (N) and a decent amount of phosphorus (P) and potassium (K). Best fertilizer for autoflowering plants at this who has an N-P-K ratio of ratio like 10-5-5 or 20-10-10. No matter what the percentage is just make sure that Nitrogen (N) is available more than those other two elements. Autoflower cannabis also needs those secondary nutes and trace elements, but commercial fertilizers usually have a mix of them included in the nutrient solution.

Nutrients for Flowering phase

When the first pre-flowers start to appear you need to change your fertilizer / nutrient solution to a mix that has more Phosphorus (P) and Potassium (K). Phosphorus is essential to cannabis bud forming and it has to be very available to autoflower plant when it enters the flowering stage. A fertilizer with a ratio of 5-10-10 or 10-20 20 will be good enough but the best auto-flower nute solutions have a 5-15-10 or similar ratios ,because Phosphorus (P) is the most essential nutrient in the flowering stage. Some inexperienced growers think that you must strictly go by the schedule when you are feeding your plants and if you don’t change your fertilizer to flowering mix then your ruderalis plant will grow very slow , but the truth is that almost any fertilizer even a 10-10-10 N-P-K mix nutrient solution will do just fine and you can give your plant it throughout its life cycle. You can be very precise and if you have have a lot of experience you can boost your yield with appropriate fertilizers but for beginners and medium level autoflower growers it is not as crucial and it is always best to give your cannabis plants less food than overfeed them.

Nutrient Overfeeding

Overfeeding autoflower cannabis plants is the most common beginner grower’s mistake and it is a serious one. You can overfeed your cannabis plants and not even know that you are harming until it is too late and your precious autoflower plant starts showing brown leafs and spots, starts wilting and dying. Usually overfeeding starts with a salt buildup in your soil. A salt-buildup occurs when you give your plants too much nutrients and they cannot absorb them in time, so the excess elements build up in the ground increasing the PH level of the soil and locking out other necessary elements. A salt buildup usually makes your ruderalis plant show a signs of nutrient deficiency but it only occurs because other elements have blocked vital nutrients and your autoflowering cannabis plant is not able to absorb them. A salt buildup can be easily  fixed with flushing.A more severe case of overfeeding can lead to a complete nutrient overdose and your precious autoflowering weed can get a toxic amount of them and then there is nothing to do but let the poor thing die and start over again.

The best way to not let your plants suffer is to give them a reasonable dose of autoflower nutes and better start slow and build up a momentum than just start feeding ½ of the recommended dose and see your cannabis leafs burn.
When an autoflwoer cannabis plant has a nutrient “burn” then it can take up to two weeks to recover and if your ruderalis plant grows only two months then two weeks is ¼ of your autoflower plants life cycle and you can imagine what that will do to your end yield.

Nutrient Underfeeding

Underfeeding in other hand is much safer extreme, because day neutral cannabis plants in nature are adapted to survive with small amount of necessary elements and they still grow just fine.
An under-fed plant will be small, have a pale green color and will in general have a sick look.
If you see that your autoflower plant stays small and have small stems and pale leafs, then maybe you are starving it from its natural food. This situation when autoflower plants are starving for nutrients occurs very rarely because cannabis ruderalis plants as I mentioned earlier is a one tough plant!
Fixing an underfed autoflowering cannabis plant is very simple, because you just need to give it mild nutrient solution and it will be just fine.
You can give your plant a small dose of fertilizer and it will recover in a day of two so you can see that under-fed autoflowering cannabis is always better than overfed (burned) cannabis plant.

My autoflower nutrient schedule

Autoflowers as i mentioned before don’t like to be over fed and they can easily get burned but nutrients are essential for any plants growth so what dosages and what nutrients can you give to your plants?

This all depends on the strain and growing environment but in general I would use 1/4 or 1/2 or the required dosage for regular cannabis plants and I would do this:

1 week(seedling) – Ph adjusted water

2 week(start of vegetative) – 1/8 veg nutes

3 week(vegetative) – 1/4 veg nutes

4 week(pre-flowering) – 1/2 veg nutes

5 week(first flowers) – 1/4 bloom nutes or 1/8 bloom and 1/8 veg nutes mix

6 week(flowering) – 1/2 bloom nutes

7 week(flowering) – 1/2 bloom nutes

8 week(flowering) – Ph adjusted water

9 week(flowering & harvest) – Ph adjusted water till harvest

This schedule can be altered depending on the time when your plant start flowering and when you see the first pre-flowers you need to start changing from vegetative to bloom nutrients. I need to also mention that this schedule is for soilless mix that has no nutrients in it so you need to supply all of them artificially.

If however I use soil with nutrients pre-added then I use a schedule like this:

1 week(seedling) – Ph adjusted water

2 week(start of vegetative) – Ph adjusted water

3 week(vegetative) – Ph adjusted water

4 week(pre-flowering) – 1/2 veg nutes

5 week(first flowers) – 1/4 bloom nutes

6 week(flowering) – 1/2 bloom nutes

7 week(flowering) – 1/2 bloom nutes

8 week(flowering) – Ph adjusted water

9 week(flowering & harvest) – Ph adjusted water till harvest

These are the two nutrient schedules I use, but you can create your own schedule depending on the nutrient strength, soil and your strain but these will help you as a starting point.

I hope you enjoyed this article and if you like to know more on autoflowering-cannabis.com you can find other helpful articles about  nutrients like :
Autoflowers and Nitogen
Autoflowering cannabis and Phosphorus
Autoflowering marijuana and Potassium

 

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19 Responses to “Nutrients for autoflowering cannabis”

  1. Madalyn says:

    Book marked, I enjoy your blog! :)

  2. mark wilson says:

    I live in the uk and I’m just starting my first grow. Its called auto #1 I’m using canna Terra pro plus soil mix with ionic soil range nutrients. Have you got any tips and have you ever used these nutrients?

  3. LM12700 says:

    i just bought autoflower seed but i need help what kind of fox farm nutrient should i feed the plant and oun when should i start feeding?i was thinking of buying the cha-chin nutrient and give it only that and feed it water till like 3 or 4 weeks int o growing need opinions

  4. scot tomson says:

    Bio bloom for me after 3 wks. Just dont give the girls too much bloom so I just give it HALF a ml all the way through and i’m happy with the results….hope u get it together. i.e. tried Cannes,no good for me but do your own thing and good/happy high luck.:}

    • the dude says:

      I have done the very same as Scot (above) with fine healthy results. Half a ml of Bio-bloom up ’til ’bout three wks left then ”ONE” dose of one ml before flushing….fly high and stay happy :)

  5. J Juror says:

    Just want to correct you where you say 10-5-5 means 10% Nitrogen, 5% phosphorus, 5% potassium.
    What it actually means is a ratio of 10 parts Nitrogen – 5 parts phosphorus – 5 parts potassium.

  6. freebyrdslim says:

    think of it as a 2-1-1 ratio on pre flower or 1-3-2 on flower stage. nitrogen = up or growth phosphorous = down or root growth. k or potassium = out or yield growth spread. n-p-k. up down out.

  7. Krishna says:

    Hi, Thanks for a wonderfull post that answered all my questions.. almost.. I wondered what if iam using powder feeding ? And i am also not sure if i should go with the indica or hybrid powder feeding.. ? hope your expertise can help me :)

    • midowo says:

      Hi, glad to help you!
      For the powder feeding I wont be able to answer any questions as I have not used it but from the reviews the Short flowering formula is designed for autoflowers so I think you should go with that!

  8. Nicolás says:

    Great article, I enjoyed reading it.
    Thanks for sharing your wisdom xd

  9. Alejandro says:

    Great article.
    I only have one question? What happens if the ratio for the pre-flowering nutrients are in the range of 14-3-6 and the flowering one has a 6-20-9? Does it affect the plant? Or is it better if it has more phosphorus?

    Thanks!

    • midowo says:

      Hi Alejandro,
      I think that it does not matter that much as the pre-flower mix is rich in Nitrogen and that flowering Mix has a lot pf Phosphorus.
      If grown for home use I think there is no distinct difference for one or two percent more or less phosphorus in the nutrient mix and if the overall mix is good (giving your plants what they need) they should grow great.

  10. Dedop says:

    I think this article is going to help out a lot. I’ve just finished my 4th grow and even though my plants end up well, they are often not the prettiest looking and look very sick during the flowering stages. They look beautiful, big and green during veg stage and then once I switch to hps, boom that’s where the troubles start. I think it’s because I’ve only been using a 2-8-4 during flower stage. I think it may be time to get some more and butter nute ratios.

    When you say

    4 week(pre-flowering) – 1/2 veg nutes

    5 week(first flowers) – 1/4 bloom nutes

    Are you going from ph water to nutes, so on 4 week maybe you water twice and once with 1/2 nutes? Just want to get an idea on that. If I can get these nutes down I think I’ll be able to yield a whole lot more. Only got 2 ounces on 2 plants last time

    Thanks for your help!

    • midowo says:

      Hi,
      I try to experiment as much as I can, so with every grow I try something new,
      Exactly at that place, yes you are correct I feed them once with plain PH water and then with Those Bloom nutrients, but that depends on the strain and your growing conditions, and this is just my take, so you have to experiment a lot to get the right amounts for your exact strain.

  11. Alejandro says:

    Hey! I’m back. It’s almost time for the bloom fertilizers, but I have one last question before I start.

    How many times do I fertilize? I mean, if I’m going to water the plant on monday, thursday and sunday do I feed them with fertilizer only on monday?

    Thanks for your help again. :)

    • midowo says:

      Hi,
      That all depends on how stong is the fertilizer and what are your plants requirements.
      It is hard to say what is the exact fertilizing schedule for your grow but I would do it every third or forth watering – so once a week.

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