Autoflowering cannabis is known for being easier to grow than photoperiod varieties, but it still needs the right combination of nutrients to thrive. It’s also critical to know how many nutes to use and when.
What Nutrients Should I Use for Autoflowering Cannabis?
The three most important macronutrients for growing cannabis, including vegetative growth, are nitrogen (N), phosphorus (P), and potassium (K). Most fertilizers are labeled with an N-P-K ratio showing how much of these nutrients they contain. The ideal N-P-K ratio varies depending on the growth period:
- Seedling phase: 2-1-2
- Vegetative stage: 10-5-5
- Flowering stage: 5-15-10 or 5-10-10
As you can see, cannabis plants need more nitrogen (N) and potassium (K) in the seedling phase, plenty of nitrogen for vegetative growth, and large quantities of phosphorus (P) for flower production.
Calcium, magnesium, and sulfur are also essential, along with trace amounts of micronutrients like copper, zinc, and iron. These are usually included in commercial fertilizers that have the three major macronutrients.
There are some nutrients designed specifically for autos, but you can also use nutes intended for photoperiod cannabis. Just make sure to avoid feeding your plants large quantities of fertilizer. Autoflowers only need one-eighth to one-half of the nutes that photos require, so we recommend starting with a low dose and increasing the strength if needed.
Best Organic Nutrients for Autoflowers
Organic nutes enrich the growing medium by breaking down existing nutrients so they can be easily absorbed. Many growers also believe they result in a better-tasting smoke.
Green Buzz Liquids, BiozBizz, and B.A.C. are some of our favorite organic nutes. Natural organic fertilizers such as manure, bat guano, and compost tea are also helpful.
Best Nutrients for Autoflowers in Soil
When growing in soil, you can start your autos off right by making or buying Super Soil, a soil mix that contains most or all of the nutes your plants need. There are many different recipes, but Super Soil can include peat, sphagnum, compost, earthworm castings, perlite, beneficial fungi and bacteria, and other natural soil amendments.
If you want to use a different soil blend, you can use almost any brand of autoflower nutes with it. Just remember not to use too much!
Best Hydroponic Nutrients for Autoflowering Cannabis
If you’re not growing in soil, we suggest feeding your autos with synthetic or liquid fertilizers, since they are easier to absorb. Terra Aquatica makes some of the best fertilizers for hydroponic growing. It’s also crucial to supplement with calcium and magnesium in addition to the main three macronutrients when growing hydroponically.
Best Brand of Nutrients for Autoflowers
FoxFarm is one of the most popular producers of fertilizer for cannabis growth, including many products that are ideal for autoflowers. Their Beastie Bloomz and Open Sesame blends are perfect for getting a full bloom during the flowering stage. A few other brands we like include Earth Juice, CANNA, Advanced Nutrients, and Humboldt’s Secret.
Growing Autoflowers without Nutrients
Thanks to their sturdy ruderalis genes, autoflowers can grow fairly well without nutes, particularly during the seedling and vegetative stages. This is especially true if you’re using good-quality soil. However, cannabis plants won’t grow well in hydroponic setups without adding nutes.
How Many Nutrients Do I Need to Use for Autoflowers?
Even with the best fertilizer, you still need to know how much to feed your autos and when. We recommend the following nutrient schedule:
- Seedling phase: Be very careful to avoid overfeeding your autos at this point. You should give them no more than one-eighth the recommended amount of nutes. If you’re using potting soil that’s enriched with nutrients, you won’t need to feed your seedlings at all.
- Vegetative growth: Autoflowers have a short vegetative phase, also known as the pre-flowering stage. Use a nitrogen-heavy fertilizer with a ratio of 10-5-5 or 20-10-10 and give your plants half the recommended amount on the label.
- Flower production: When you notice your plants starting to form flowers, switch to a fertilizer with more phosphorus and potassium to encourage full bloom. A 5-15-10 ratio is ideal, but 5-10-10 or 10-20-20 should also give you a good harvest. Again, give your plants no more than half the recommended amount.
When transitioning between different growth periods, don’t switch immediately from one type of fertilizer to another. Instead, gradually decrease the amount of one as you increase the new one to avoid stressing your plants.
You also don’t need to feed your plant every time you water – just add nutes every second or third time you water for the ideal nutrient schedule.
When feeding your plants, try to avoid overfeeding or underfeeding. Overfeeding can cause nutrient burn, and it’s hard for autoflowering plants to recover from this stress since they have a shorter life cycle than photos. (If you do experience nutrient burn, you can flush your plants with plain water to help them recover.) Underfeeding, on the other hand, can result in a disappointing harvest.
You’ll also want to make sure that your growing medium is at the optimal pH so your plants can absorb the nutes. The optimal pH for cannabis growth varies depending on your growing medium – about 6.0 to 7.0 for soil and 5.5 to 6.5 for hydroponics.