Best nutrients for autoflowers

Autoflower strains, the resilient and adaptable cousins of traditional cannabis plants, require specific nutrients to thrive and reach their full potential. From nitrogen to phosphorus and potassium, discovering the best combination of essential elements is process that can only be refined with experience. Join us as we delve into the fascinating world of autoflower nutrition and uncover the secrets of their success.

What are the advantages of growing autoflowering strains?

Autoflowering strains of cannabis offer several advantages over traditional photoperiod strains, including:

  • Faster Growing Cycle: Autoflowers have a shorter growing cycle, typically taking only 10-12 weeks from seed to harvest, compared to traditional strains that can take several months.
  • Ease of Cultivation: Autoflowers are easier to grow, as they do not require a specific light schedule, making them a good option for beginner cultivators or those with limited space.
  • Discreetness: Due to their small size, autoflowers can be grown in a variety of settings, making them a good option for those who want to grow discreetly.
  • Resilience: Autoflowers are generally more resilient and adaptable, able to withstand a wider range of growing conditions and environmental stresses.
  • Multiple Harvests: Autoflowers can be grown multiple times per year, allowing for more frequent harvests and a higher potential yield over the course of a year.

Can you give autoflowers nutrients?

Yes, you can use nutrients with autoflowering cannabis strains. In fact, providing the right balance of nutrients will help to aid the health, growth, and overall yield of autoflowers.

When should you begin feeding nutrients?

As for when to start giving autoflowers nutrients, it’s best to wait until the plants have established a good root system. Ideally you should allow a plant 1-2 weeks after germination to get through the early seedling stage. Once you see 2-3 sets of proper leaves you can start introducing nutrients. However, bear in mind that because of their size autoflowers need less nutrients than photoperiods, this will be explained further on in the article in more detail.

It’s important to monitor the plants closely and adjust the nutrient levels as needed to ensure they receive the right balance of elements for optimal growth. Over-fertilization can lead to nutrient burn, stunted growth, and reduced yields, so it’s crucial to follow the recommended guidelines and adjust the levels as necessary.

What are the main nutrients that autoflowers require?

Autoflowering cannabis plants require a balance blend of essential macro and micronutrients for optimal growth and yield. The three primary macronutrients are normally that autoflowers require are:

  • Nitrogen (N): Nitrogen is essential for the growth of leaves and the development of the plant’s structural framework.
  • Phosphorus (P): Phosphorus is important for root growth, flower and fruit development, and energy transfer within the plant.
  • Potassium (K): Potassium plays a role in regulating water balance, enhancing stress tolerance, and improving the overall health and vitality of the plant.

In addition to these macronutrients, cannabis plants also require micronutrients such as calcium, magnesium, sulfur, iron, manganese, copper, and zinc. It’s vital to provide the right balance of these nutrients throughout the growing cycle, because deficiencies can lead to stunted growth, yellowing leaves, and reduced yields. Equally over feeding these nutrients can lead to nutrient burn and lockout.

When you are shopping for nutrients you should look out for the abbreviation NPK, standing for nitrogen, phosphorus and sulfur. These will normally be displayed on the packaging as ratios. For example, ‘NPK: 10-5-7’ would mean the solution contains 10 parts nitrogen, 5 phosphorus and 7 sulfur. This ratio would be used to feed a cannabis during the vegetative stage of growth where a plant requires more nitrogen to fuel its growth.

What is the best nutrient Ratio schedule for autoflowers?

Each cannabis strain will require varying levels of nutrients, some are heavy feeders and others not so much. So, there isn’t a hard and fast rule for exactly how much nutrients you should feed your plants. However, the NPK levels in your nutrient solution will need to be increased or decreased depending on the stage of growth that your plants are in. Below is a basic nutrient ratio schedule that will work with almost all autoflowering strains. Bear in mind that this is sort of like a universal schedule so you can start with this and then increase or decrease the numbers according to how your plant responds. You may also want to incorporate this to your autoflowers nutrient feeding schedule.

You will notice in the table below that it states either ⅛, ¼, or ½ of veg or bloom nutrients. This is because when you go out and purchase your cannabis nutrients, most brands produce them for photoperiod cannabis plants. Autoflowering strains are much smaller and so you need to use a smaller dose of nutrients so as not to cause nutrient burn. Follow the fractions in the table below and this should be a safe guide of how much you can safely give your autoflowering plants.

Growth StageNPK Nutrient Ratio
Seedling stage No Nutrients – Plain pH’d water
Early Veg stage4-2-3 (⅛ veg nutrients) 
Vegetative stage10-5-5 (¼ – ½ veg nutrients)
Flowering stage5-15-10 (¼ – ½ bloom nutrients)
Flushing stage (last week)Plain pH’d water
NPK ratios for autoflowering plants throughout their growth stages

What are the best nutrients for increasing autoflower bud size?

To increase the size of buds in autoflowering cannabis plants, it is important to provide a balanced blend of essential nutrients throughout the flowering stage. Some specific nutrients that can help to promote larger buds include:

Phosphorus (P): Phosphorus is essential for flower and fruit development and is often considered the “bloom booster” nutrient. Increasing the phosphorus levels during the flowering stage can help to promote larger, denser buds.

Potassium (K): Potassium helps to regulate water balance, improve stress tolerance, and enhance the overall health and vitality of the plant. Providing adequate levels of potassium during the flowering stage can help to support the growth of larger buds.

Magnesium (Mg): Magnesium is a crucial component of chlorophyll, the molecule responsible for capturing light energy and converting it into chemical energy for the plant. Adequate levels of magnesium can help to increase the overall size and weight of buds.

Calcium (Ca): Calcium plays a key role in cell division and growth, and is essential for the development of strong stems and branches. Providing adequate levels of calcium can help to support the growth of larger buds.

Although adding these nutrients at the right time will help to fatten the buds of your cannabis plants, using LST training methods will also increase yield and bud density.

What is nutrient burn and how to spot the signs?

Nutrient burn occurs when a plant receives too much nutrients which can cause yellowing, browning, and curling of leaves. Here are the main signs to look out for:

Yellowing leaves: The first sign of nutrient burn is yellowing of the leaves, starting at the tips and then spreading inward. This is a result of the plant being unable to absorb excess nutrients.

Browning leaves: As the burn worsens, the yellowing may turn to brown, and the leaves may become crispy and brittle.

Curling leaves: The leaves of a plant may also start to curl inward or downward. This is a sign that the plant is trying to conserve moisture and energy.

Stunted growth: A plant with nutrient burn may also experience stunted growth and a general lack of health.

Root damage: In the worst of cases, the roots of the plant can become damaged, which can impact the plant’s ability to absorb water and nutrients. This is sometimes referred to as nutrient lockout.

If you suspect your plant is experiencing nutrient burn, it’s important to immediately reduce the amount of nutrients you are providing and make sure that you are not over-fertilizing. It may also be helpful to flush the soil with clean pH’d water to remove any excess nutrients.

Cannabis plants showing signs of nutrient burn
Can you spot the signs? Yellowing tips, brown tips, and curling leaves on these plants are screaming nutrient burn!
A cannabis plant with severe nutrient burn
Severe nutrient burn caused a lot more damage on this plant

Should you use organic or synthetic autoflower nutrients?

Organic and synthetic nutrients are two different types of fertilizers that are used to provide nutrients to autoflowering cannabis plants. Both have their pros and cons so it’s really down to personal preference which route you choose. Generally, growers that prefer a more organic, natural approach use organic nutes whereas those that are growing for bigger or faster results tend to grow using synthetic.

One thing to bear in mind is that although you may be able to grow faster using synthetic nutrients, most growers do a 1-2 week flush at the end to clear any leftover nutrients out of the cannabis plants.

If you are growing hydroponically then you will need to use synthetic nutrients because the growing mediums used with hydro do not contain any nutrients and do not retain any either. Mediums such as clay pebbles offer no actual nutritional value to the plant, however, they work great when used in a hydro set up with a constant supply of synthetic nutrients.

Organic vs. synthetic nutrients

Source: Organic nutrients come from natural sources, such as compost, bat guano, worm castings, bone meal, fish meal, and seaweed, while synthetic nutrients are chemically manufactured in a laboratory.

Composition: Organic nutrients are made up of complex molecules that are broken down over time by microbes living in the soil. While synthetic nutrients are made up of simple, readily available ions that are immediately available to the plant.

Release: Organic nutrients release their nutrients slowly over time, providing a steady source of nutrition to the plant. Synthetic nutrients, on the other hand, release their nutrients quickly and can cause nutrient burn if not used carefully.

pH: Organic nutrients are often less pH-stable than synthetic nutrients, meaning that the pH of the soil or water can affect their effectiveness.

Availability: Organic nutrients may not be readily available in all regions and may be more expensive than synthetic nutrients. Synthetic nutrients are widely available and are often more cost-effective.

Making your own organic soil blend

Organic nutrients are becoming more and more popular among cannabis growers because of the environmental benefits and smaller carbon footprint. You can buy readymade organic and living soils from most garden centers, however, you can also make your own organic soil mix that is tailored towards cannabis by following the recipe below.

1 part compost – Compost provides nutrients and organic matter to soil, improves soil structure, helps retain moisture, reduces the need for chemical fertilizers, increases soil biodiversity, and contributes to healthy plant growth and yields for autoflowers.

1 part worm castings – Worm castings are a rich source of plant nutrients, contain beneficial microorganisms, improve soil structure and drainage, enhance root growth and plant health, reduce the need for synthetic fertilizers, and promote high yields for autoflowers.

1 part bat guano – Bat guano is an excellent organic fertilizer that provides plants with essential nutrients, improves soil fertility and structure, increases microbial activity, boosts plant growth and yields, reduces dependence on chemical fertilizers, and contributes to sustainable growing practices for autoflowers.

1 part vermiculite – Vermiculite is a handy soil amendment that improves water retention, aeration, and nutrient uptake. It reduces soil density helping root growth, it also creates air pockets in the soil which provides insulation and protection from extreme temperatures.

Simple and effective, this organic mixture will provide plenty of natural nutrients for your autoflowers from seedling right the way through to harvest. If you want to add a little boost to your grow you can also add some other organic soil dressings as the plants approach flowering. Bat guano and kelp meal provide good amounts of phosphorus and potassium which are key ingredients to the cannabis flowering stage.

What are the best synthetic autoflower nutrients?

There are plenty of brands out there that make perfectly good nutrients for cannabis, the most important thing to remember is that you need to reduce the amount of nutrients and stick to the nutrient ratio’s in the chart above. A popular nutrient brand is Fox Farm they have a three part nutrient pack that offers everything a cannabis plant should require to grow through the vegetative and flowering stages. Just remember to adjust the numbers before you feed to avoid nutrient burn.

If you haven’t made your mind up whether to go organic or synthetic you can go somewhere in between and use a nutrient solution such as Bio Canna. Bio Canna is from the well-known nutrient brand Canna and is a readymade 100% organic solution in a bottle. Perfect for anyone that wants to grow organically but doesn’t necessarily want to make their own organic soil blend.

Joe Musgrave

An avid 420 enthusiast, grower, smoker and writer. Joe writes non stop, sharing his extensive knowledge in the field of cannabis with the wider online 420 community through blogs like ours at High Yield Strains.

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