What are the best nutrients for autoflowering cannabis?

Autoflowers can save the day when it comes to faster harvests, manageable plant sizes, simpler lighting requirements, and more. However, when growing autoflowers vs. regular or feminized seeds, there are some nuances. If you want to maximize yields and quality in your home grow, consider the best nutrients for autoflowering and know how autoflowers differ from photoperiod plants.

Do autoflowers need special nutrients? 

There’s no argument that nutrients are essential to plant growth. The chemicals needed to feed autoflowers in soil, hydro, or other environments aren’t that different. Nutes for autoflowers differ mostly in concentration and timing. 

Getting nutrients for autoflowers can be done by watering, amending the soil, or using slow-release powders. When it comes to autoflowers, remember that you can always add more to correct a deficiency, but you can’t easily take nutrients out to reduce excess. Autoflowers get their name from the fact that they flower and mature as they age. So, any nutritional stress should be avoided since it can slow them down. 

Adding the correct nutrients will maximize your yields, which are already huge for the size of the plants (and speed) that autoflowers grow. Get your autoflower seeds below, add some nutrients and start growing.

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Is there a difference between nutrients for autoflower and photoperiod flowers?

There are minor differences when discussing autoflowering nutrients versus those used for photoperiod cultivars. Many nutrient lines are designed for photoperiod plants and must be adjusted when growing autoflowers. Due to the ruderalis lineage, autos’ trace nutrient requirements are lower, but they still require the same macro and micronutrients as photos. Pay attention to the growing media and trace elements to avoid overwhelming your autos.

The quantity and concentration of nutrients needed for autos are lower than for photoperiod plants. This is due to the smaller stature of autos and their finite lifecycle. For the home grower, this is great all around because we can keep plants small enough to fit in tents and grow rooms while saving money on nutrients by using less overall.

Ph levels are similar for autos but can affect the nutrient uptake of your beautiful plants if not monitored and kept within normal ranges. The typical 5.5 -6.5 will work, but assess your plant’s health to fine-tune that number, as it’s also dependent on the environment and grow medium.

Autoflowering cannabis plants have different nutritional requirements than photoperiod cannabis plants. Download my FREE marijuana grow bible and start growing high quality auto strains

The best nutes for autoflowering plants

Looking for the best nutrients for autoflowers doesn’t mean looking for different nutrients. You’ll still be feeding the big three Nitrogen (N), Phosphorus (P), and Potassium (K). You can adjust photo nutrient lines to work just fine, or you can find autoflower-specific nutrients that have already been reduced and prepared for autos. Along with NPK, there are regular needs for other elements like Magnesium (Mg), Calcium (Ca), and Sulfur (S), also at reduced concentrations. These are accompanied by trace elements in even lower quantities, Boron (B), Copper (Cu), Zinc (Zn), Iron (Fe), Manganese (Mn), and Molybdenum (Mo).

If the growing medium has already been enriched with nutrients, your autos may not need supplementation if it has been pre-amended. A relatively inert medium can be a good place to start with autos. One macro to watch specifically in soils is the Nitrogen level; it can be very high in some lines. To make matters more interesting, different cultivars may need different adjustments to macros, micros, and grow medium

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What nutrients do autoflowers need? 

Major or macronutrients for autoflower plants

  • Nitrogen (N): Is a key component of amino acids, which form the building blocks of plant proteins and enzymes. Needed for fast and healthy growth, especially in the early stages. 
  • Phosphorus (P): Required for photosynthesis and plant development.
  • Potassium (K): Allows the plant to regulate stomata and optimize CO2 & water use.

Minor or micronutrients for autoflower plants

  • Magnesium (Mg): Used in many processes and a necessary element for chlorophyll.
  • Calcium (Ca): Major component of plant cell walls.
  • Sulfur (S): Needed for Nitrogen absorption, resilience, chlorophyll, and more.

Trace elements for autoflower plants

  • Boron (B): Important for structural components of the plant.
  • Copper (Cu): Essential for several systems, including chlorophyll production.
  • Zinc (Zn): Contributes to internode elongation and growth hormone
  • Iron (Fe): Aids in nitrogen-fixing, chloroplast production, and photosynthesis.
  • Manganese (Mn): Assists in the production of many enzymes and plays a role in photosynthesis.
  • Molybdenum (Mo): Allows the plant to break nitrates down to amino acids (nitrogen-fixing)

Best organic nutrients for autoflowers 

Organic nutrient options are ideal for aroma and flavor. These are available specifically for autoflowers or can be adjusted from nutrient lines meant for photoperiod plants. Bacterial and fungal teas contain soluble plant nutrients ready for fertilizing autoflowers.  For high-quality organic soils, many nutrients will be provided in the soil. Start with a low level of additional nutrients and adjust as needed. 

Best nutrients for autoflowers in soil 

Inorganic nutrients are also used in autoflower nutrient kits, or they can be fed using reduced quantities of photoperiod nutrient lines. Watch carefully for any signs of stress and fine-tune your operation.  Remember, a little goes a long way. Regular garden variety soils will need supplementation, whereas super soils may be hearty enough to see your plants through with minor supplementation. 

Bergman's feeding schedule for soil
Bergman’s feeding schedule for soil

Best hydroponic nutrients for autoflowering cannabis 

When it comes to the best hydroponic nutrients for autoflowering, pay close attention to the fertilization instructions, as the roots will be directly absorbing anything put into the system. This can be great for autoflower hydro but also can be overdone quickly if you’re not on top of measurements. Plants grown this way depend on you from step one, where those in soil or other mediums have additional supplementation to use in the early stages.  

Bergman's feeding schedule for hydroponic nutrients
Bergman’s feeding schedule for hydroponic nutrients

Autoflower fertilizer needed by growing stage

The ratios and nutrient needs change throughout the plant’s lifecycle. From the early seedling stages all the way through flush, the best autoflower nutrients are those selected with lifecycle, cultivar, growing medium, and environment in mind. 

Nutes for autoflowers in the seedling stage 

The seedling will thrive for the first few weeks with nothing but water as its resources are used. 11-40-13 NPK soil mixes can give young plants a little extra love as they start out. For hydro and other inert mediums, some nutrient solution is okay under 175ppm at ⅛ of the measured photoperiod amount.

Seedling fertilizer
Seedling fertilizer

Nutes for autoflowers in the vegetative stage

The vegetative stage for autoflowers is condensed as the plant switches from early veg to flower quickly and doesn’t truly veg like a photoperiod variety. At this stage, the best nutrients for autoflowering will have a slightly higher nitrogen ratio. 3-1-2 nutrients will work at this stage but reduce the measurements by a quarter at first and only add more if you notice deficiencies.  

Nutrients for the vegetative stage
Nutrients for the vegetative stage

Nutes for autoflowers in the flowering stage

Bloom nutrients for autoflowers can be derived from photoperiod nutrients by reducing the quantity by ½. This is the time of the plant’s life cycle when phosphorus is very important; consider 2-8-4 mixes. After the first two weeks of true flowering, the last two weeks should be used to flush and clear out nutrient and mineral buildup in the plant before harvest.  

Blooming nutrients
Blooming nutrients

Indoor vs. outdoor nutrients for autoflowering cannabis 

The conversation around nutrients for autoflowers can also be looked at through the lens of indoor vs. outdoor cultivation. Autoflowers outdoors have similar nutrient requirements but will be affected by the soil and environment, so use caution in overfeeding. A 3-1-2/2-1-3 in veg and 2-8-4/1-3-2 in flower will work the same way but should be cut down to at least ⅛ measurements at first. 

Autoflowers outdoors get one major benefit that their indoor counterparts do not in the form of naturally occurring arbuscular mycorrhizal fungi. These create mycorrhizae which help the plant optimize its nutrient use and water consumption. Worms can also help in outdoor farming, and fermented compost methods like Korean Natural Farming can be used to culture the beneficial mycorrhizae in your area. 

The best nutrients for autoflower aren’t exactly different from those used in photoperiod plants. The takeaway is to dilute your fertilizer for autoflowers from ⅛ to ½ as the plants get older and relative to your cultivars, environment, and growth medium. An autoflower nutrient schedule should allow for two weeks of early seedling growth and two weeks of flush with pure water with a change from veg nutes to bloom when your plants enter early flowering stages

Bergman’s plant food by ILGM will see your autoflowers through the entire growing process. Although it is made with photoperiods in mind, using the dilutions we’ve discussed here, it can be the answer for your grow. Start slow with nutrients and keep it simple to avoid overstressing your plants. 

Know how to perfectly time your harvest so you can maximize your yield. Download our free mini harvesting guide

FAQs about autoflower nutrients

What does Cal Mag do for Autoflowers?

Cal-Mag works for autoflowers the same way it does for photoperiod plants. Calcium is an important building block for plant cell walls, and Magnesium is needed to form chlorophyll. 5ml to a gallon should be enough for most plants. 

Should I use nutrients every time I water?

There are a lot of factors to consider here; it really depends on the situation and the medium. It’s fine to use nutrients every time in an inert medium, but in other mediums, space them out based on the plant’s look and health.

What does Epsom salt do for Autoflowers?

Epsom salt is a readily available organic way to supplement magnesium and sulfur for plants to boost their immune systems and assist in the all-important nitrogen fixation process.

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Mr Rob Sanchez

Cannabis Cultivation Expert

Rob started cultivating in 2011 and worked in Colorado's medical days as a cultivator and hash maker before getting involved ... See profile

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