Nutrients for Autoflowering Cannabis

All autoflowering cannabis plants like any other living thing need food to stay alive and grow. But unlike animals or humans, plants use nutrients for this matter.

Automatic 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 its 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 decent amounts of nutrients and you need to supply your plant with all the necessary “foods” so you can get amazing harvests and fast growth.

However, 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 but from that point on you will need to supply additional nutrients so there are no deficiencies.

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 plants show signs of nutrient deficiency when they have run out of “food” and this is the time when you need to add additional chemicals. If you are growing very fast-growing autoflowering strains that can be done in less than two months from seed then the premium soil will almost able to supply your auto plant with the necessary amounts of nutrients and you will probably need to feed them only once or twice. This statement is only true if you use a large pot and small growing auto seeds because small pots contain less soil and fewer nutrients so you can imagine how the plant will use it up a lot faster.

If you use regular soilless-mix or ordinary soil without any added nutrients you will need to add all these necessary elements yourself while the plants are growing. But be careful with time-release nutrients as they can do more harm than good.

The 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 as well as flowers and without these elements, your plant struggles to survive.

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 a liquid solution(water) where all these elements are dissolved.

Autoflowering cannabis are very delicate plants that require a lesser amount of food than ordinary cannabis strains. This property of autoflowers 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 these plants. In nature cannabis ruderalis plants require a very low amount of nutrients to survive and that is why you need to give your autoflowers small amounts of nutrients and never overfeed 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 only 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 so the possibilities are endless, and you need to experiment and see what works best for you and you and your autoflower plants.

Nutrients for Seedling phase

The 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 better yet, 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 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 go 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 leaves 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 photo-sensitive plant in its vegetative stage.

When we see that our autoflower plant starts really fast growth we need to start giving it a 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 a lot of Nitrogen (N) and a decent amount of phosphorus (P) and potassium (K). The best fertilizer for autoflowering plants at this growth stage is the one that has an N-P-K ratio of 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 not grow properly. 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 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 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 leaves or brown spots, starts wilting, or even dying.

Usually overfeeding starts with a salt buildup in your soil. A salt-buildup occurs when you give your plants too many 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 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. It 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 with new seeds.

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 momentum than just start feeding ½ of the recommended dose and see your cannabis leaves burn.

When an autoflower 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 plant’s life cycle and you can imagine what that will do to your end yield.

Nutrient Underfeeding

Underfeeding, on the other hand, is much safer extreme because day-neutral cannabis plants in nature are adapted to survive with a 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 leaves, 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 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 autoflower is always better than overfed (burned) cannabis plant.

My autoflower nutrient schedule

Autoflowers as I mentioned before don’t like to be overfed and they can easily get burned but nutrients are essential for any plant 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 am using 1/4 or 1/2 or the required dosage for regular cannabis plants and I keep to these schedules:

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 starts 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 a 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) – 1/8 bloom nutes + 1/8 veg 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 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 check out other helpful articles about nutrients like:

• Autoflowers and Nitrogen
• Autoflowering cannabis and Phosphorus
• Autoflowering marijuana and Potassium
• Autoflower secondary nutrients