What is the best soil for autoflowers cannabis

Autoflowers are versatile and can thrive indoors or outdoors, providing they have good soil. So, what makes a good soil for autoflower strains? The short answer is soils that are light, well aerated, nutrient-rich with a balance of good drainage and water retention. Sounds easy enough, well how do we achieve this? This article covers all you need to know about creating the best soil for autoflowers. We’ll discuss the attributes of ideal soil, why these features matter, and how you can replicate these conditions at home. From pH balance, nutrient content, to soil texture and composition, you’ll be equipped with knowledge to give your autoflowers a blooming start.

What type of soil mix is best for for autoflowers?

A good soil mixture is light, well-aerated, and packed with essential nutrients. These qualities promote root growth and plant health, ensuring your autoflowers reach their maximum potential and provide plenty of buds.

Lightness and aeration in the soil are crucial as they allow the roots of your autoflowers to grow freely while providing good drainage. A nutrient-rich medium feeds your plants, supporting strong and healthy growth. You should avoid dense and compact soil can hinder growth by limiting root expansion and making nutrient absorption difficult.

Autoflowers typically prefer a light, well-aerated soil with a relatively low level of nutrients. Here are five key things you can add to the soil to improve it for autoflowering cannabis plants:

  1. Light Mix Soil: This is a type of commercial soil specifically designed for autoflowering plants. It contains fewer nutrients than other mixes, making it less likely that your plants will suffer from nutrient burn.
  2. Perlite: Perlite helps to aerate the soil and improve drainage and helps young roots grow.
  3. Worm Castings: These add organic matter to your soil and provide a slow-release form of nutrients, which is perfect for autoflowers. They also aid in improving soil structure.
  4. Bat Guano: This is a rich source of phosphorus that promotes healthy root and flower development. Phosphorus is required mostly during the flowering stage, so you can add it as a soil dressing when you start to see the first preflowers, this will allow the nutrients to filter down when its watered.
  5. Mycorrhizal Fungi: These beneficial fungi can form a symbiotic relationship with the plant roots, helping them absorb nutrients more effectively. This can be particularly beneficial for autoflowers due to their short vegetative stage and rapid transition to flowering.

Remember, with autoflowers, less is often more when it comes to nutrients, and overfeeding can lead to problems. It’s also worth noting that pH management is important to ensure that the nutrients in the soil are available to the plants. A soil pH between 6.0 and 7.0 is typically suitable for cannabis plants.

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What is the best store bought soil for autoflowers?

For beginners or those pressed for time, purchasing a ready-made store bought soil mix is still a great option. Look for soil marketed specifically for cannabis or autoflowers. These are typically high in organic matter and have the necessary pH balance to support autoflower growth. Notable brands to consider include FoxFarm’s Ocean Forest Soil Mix and Mother Earth’s Coco Plus Perlite Mix. Alternatively if you are buying from a garden centre and not a grow shop you can also use a ready made soil or compost mixture. However, make sure you check that the pH level falls between 6 – 7 before you plant your autoflowers.

How to make the best soil mix for autoflowers

Creating your very own super soil may sound complicated but its actually pretty simple and everything you need you can pick up from most garden centres. It is also an excellent way to have full control over what your plants feed on. A recommended recipe includes compost, perlite, bat guano, worm castings, and coco coir.

Use the below super soil recipe below to provide all of the nutrients that your autoflowers will need in a well-draining soil.

  • 2 Parts compost – Compost serves as an excellent source of organic matter and nutrients, while perlite enhances soil aeration and drainage.
  • 1 Part bat guano – Bat guano, rich in nitrogen and phosphorous, promotes robust vegetative growth and flowering.
  • 1 Part worm castings – Worm castings supply necessary minerals and beneficial microbes.
  • 1 Part coco coir – Coco coir, on the other hand, improves moisture retention while also providing aeration.
  • 1 part perlite – Perlite contains no nutritional value, however it improves drainage and reduces soil density.

Using organic living soil for autoflower cannabis

Living soil is soil teeming with beneficial microbes that help break down organic matter into nutrients readily absorbed by plants. Using living soil for autoflowers can enhance plant health and growth, as the beneficial microbes establish a symbiotic relationship with the plant roots, aiding in nutrient uptake. Organic soil blends for cannabis are usually made up of a variety of organic matter including compost, moss, bone meal, bat guano and worm castings.

The reason we love using organic living soils so much with autoflowers is that they require a lot less nutrients that your average photoperiod. So, in some cases using a living soil can provide enough nutrients to grow from seed right the way through to harvest. And if you want to top up your bloom nutrients then just add an organic soil dressing of bat guano during the flowering stage.

The benefits of organic soil for autoflower seeds

  1. Enhanced Nutrient Uptake: Living soils contain beneficial microbes that aid in efficient nutrient absorption, promoting healthier autoflowers.
  2. Improved Flavor and Potency: These soils can boost terpene and cannabinoid profiles, enhancing taste and effects.
  3. Eco-Friendly: Reduces the need for chemical fertilizers and pesticides, supporting sustainable farming.
  4. Cost-Effective: Reduces long-term expenses on fertilizers and allows soil reuse over multiple cycles.
  5. Forgiving for Growers: Offers a buffer against common cultivation mistakes due to its natural balancing properties.

Best soil for growing autoflowers outdoor

If you’re growing autoflowers outdoors, the best soil is a loamy one. Loamy soil, a mix of sand, silt, and clay, offers optimal drainage and nutrient-holding capacity. If your garden soil is too clayey and dense, amending with organic matter like compost, perlite and coco coir or well-rotted manure will improve its structure and consistency making it retain more water and nutrients.

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Improving drainage in soils

Good drainage is essential if you want to prevent waterlogged roots. You can easily improve the drainage of your soil by adding coarse amendments like perlite, sand, or small stones. Adding these will create tiny pockets of air preventing the soil clumping together allowing water to drain through more easily.

Here are some materials you can add to cannabis soil to improve its drainage capabilities:

  • Perlite: This is a volcanic glass that has been heated until it expands. It is lightweight and does not compact, making it an excellent choice for improving drainage and aeration in soil.
  • Vermiculite: While it helps with water retention, vermiculite can also improve soil drainage due to its ability to create space within the soil for air and water to move freely.
  • Sand: Coarse sand can improve drainage in your soil by separating the soil particles and creating channels for water to flow through.
  • Pumice: Similar to perlite, pumice is a type of volcanic rock that can improve drainage and aeration in your soil.
  • Coconut coir: Although it retains water well, coconut coir also has good drainage and aeration properties. It can help prevent the soil from becoming waterlogged.
  • Bark chips: They improve drainage and also add organic matter as they decompose.
  • Gravel or small stones: They can be used at the bottom of the pot to improve overall drainage.
  • Rice hulls: They’re light, improve soil structure, and add excellent drainage capacity.
  • Composted pine bark: It improves drainage and adds some acidity to the soil, which cannabis plants appreciate.

How to tell if your soil is too dense

If your soil is too dense, it may can prevent the roots growing, water from draining, and oxygen circulating, this all leads to poor plant health. Here’s how you can test if your soil is too compacted or dense:

  1. Water Drainage Test: Water the soil thoroughly and observe how long it takes to drain. If water pools on the surface or takes a very long time to seep in, your soil may be too dense.
  2. The Penetration Test: Try to insert a stick, pencil, or finger into the soil. If you find it difficult to penetrate without applying substantial force, the soil is likely compacted.
  3. Root Growth: Inspect the roots of a plant growing in the soil. Stunted or twisted roots, or roots that grow horizontally because they can’t penetrate downwards, indicate dense soil.
  4. Soil Texture: Pick up a handful of moist soil and squeeze it. If it forms a tight, hard lump that doesn’t crumble easily when poked, it’s likely too dense.
  5. Plant Health: Plants in compacted soil often exhibit stunted growth, yellowing leaves, or signs of water stress even after watering, due to poor water and air movement in the soil.
  6. Observing Soil Layers: If you dig a small hole and notice distinct, hard layers or a “pan” within the soil profile, this can indicate compaction.

To fix dense soil, consider incorporating organic matter like compost or well-rotted manure. You can also mix in sand or perlite to improve drainage and aeration. Periodic aeration of lawns or larger garden areas can also help alleviate compaction.

Raised beds improve soil drainage

Raised beds or mounds can also help by preventing water from pooling at the bottom of your pots or plant beds. If you are growing in pots, putting them ontop of some bricks making sure not to cover any holes in the bottom will have the same effect. And in plant beds you can simply add a layer of rocks, bricks or pebbles at the bottom before you lay down any soil.

Choose the right pots for your autoflowers

To further improve drainage also consider the type of pot you are using to grow your plants. Some of the best pots for cannabis are smart pots, they are made of a breathable membrane that offers excellent drainage and keeps the soil and roots of your plants nice and cool.

Remember that while drainage is important, you don’t want to create a growing medium that drains so quickly it doesn’t hold the water and nutrients cannabis plants need. The goal is to achieve a balance between water retention and drainage.

Improving water retention in soils

While drainage is important, retaining moisture in soil is also vital to ensure your autoflowers have access to water and nutrients. Organic matter, such as compost or peat moss will improve water retention by increasing the soil’s capacity to hold onto water molecules.

Here are some amendments that you can add to cannabis soil to improve its water retention:

  • Coco Coir: This is a byproduct of the coconut industry and is renowned for its high water retention ability.
  • Vermiculite: This naturally occurring mineral can hold large amounts of water, making it ideal for increasing soil water retention.
  • Peat Moss: This is an organic material that retains water well and also helps improve soil structure.
  • Compost: High-quality compost can not only provide nutrients for your plants but also improve the water-holding capacity of your soil.
  • Sphagnum Moss: This type of moss has fantastic water retention abilities and can be added to your soil mix to help keep it moist.
  • Clay Materials: Clay soils have high water retention capabilities due to their structure, but they can also limit drainage, so they should be used judiciously.
  • Biochar: This highly porous charcoal can hold large amounts of water and nutrients, enhancing the soil’s fertility and water retention ability.
  • Hydrogels / Water crystals: These absorb and hold water, then release it slowly when the soil dries out.

Remember to balance water retention with good drainage. While cannabis plants need a constant supply of water, they also require oxygen at the roots and do not like “wet feet”. Too much water can lead to root rot and host of other issues.

Best soil for growing autoflowers indoors

When growing autoflowers indoors if you are only growing a small number of plants and don’t want to make your own soil mix, using a pre-made potting mix is the easiest option. High quality potting soils are light, well draining, and nutrient rich, perfect for autoflowers. Again, the FoxFarm Ocean Forest Soil Mix is a great choice. If you have a local garden center most potting soils or living soils can be used for indoor growing. It is best to also purchase some perlite as well to increase the airiness of the soil.

Equally if you are growing a large number of autoflowering plants indoors then making your own soil mixture will be the best way to get the perfect consistency without breaking the bank.

Best nutrients for autoflower soil

Autoflowers require a range of micro and macto nutrients, the most critical being Nitrogen (N), Phosphorous (P), and Potassium (K). N promotes vegetative growth, P aids in flower development, and K supports overall plant health.

Amending your soil with bone meal or rock phosphate can provide extra phosphorous, while greensand or wood ash can supply additional potassium. During the last one to two weeks of growth, flushing the soil of nutrients with plain pH adjusted water for a week will help improve the taste and quality of your harvested buds.

Here are the 5 key nutrients you should make sure a soil mixture contains for a healthy autoflower grow:

  • Nitrogen (N): Crucial for the vegetative growth phase, it aids in the production of chlorophyll and proteins. Can be added through amendments such as blood meal, worm castings, or alfalfa meal.
  • Phosphorous (P): Essential for flower development and root health. Bone meal or rock phosphate are great amendments to boost phosphorous levels in your soil.
  • Potassium (K): Supports overall plant health and resistance to diseases. Greensand or wood ash can be added to your soil to supply additional potassium.
  • Calcium (Ca) and Magnesium (Mg): Often overlooked, these nutrients are vital for plant cell structure and chlorophyll production. Dolomite lime or gypsum can be used to supplement calcium, and Epsom salts for magnesium.
  • Flushing of Nutrients: In the final one to two weeks of growth, flushing the soil helps to remove excess nutrients and salts, improving the taste and quality of your harvested buds. This involves watering your plants with pH balanced water only, with no added nutrients.

Remember, each amendment should be used judiciously and in the right phase of growth to avoid overfeeding, which can lead to nutrient burn or other issues. Soil pH should also be monitored to ensure nutrient availability to the plants. Cannabis prefers a slightly acidic soil with a pH range of 6.0 to 7.0. If signs of nutrient lockout or incorrect pH level start to show, consider flushing the plants with plain water to clear the buds of any leftover nutrients before you harvest them.

Is miracle grow good for autoflowers?

Miracle Grow, a popular plant food, can be used for autoflowers. However, caution is advised as it can easily lead to nutrient burn due to its high concentration. It’s recommended to start with a half-dose and adjust based on your plants’ response.

Remember, the “best soil for autoflowers” depends on whether you are growing in soil, hydro, indoors or outdoors. However, armed with this knowledge, you should be ready to go out and create your own living soil or simply buy a suitable store bought soil for your autos.

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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