Selecting the best autoflowering genetics is one half of growing amazing buds, and working with the best growing medium, and nutrients is the other half. This article explains the best soil for growing autoflowers, key characteristics for soil, how to make amendments, mixing your custom soil, monitoring pH and watering strategies to produce the best autoflowering results.
Understanding autoflowering cannabis soil requirements
While autoflowering cannabis plants are incredible performers, tough, resilient, and an excellent choice for first-time or expert-level growers, understanding what soil requirements autos need will guarantee your future success as a cultivator.
Autoflowering genetics will flower automatically once they are 28 days old. Making sure they have the optimal balance of nutrients, aeration, drainage, water retention and correct pH levels to get them thriving from seed to harvest is a crucial part of obtaining superb results, with little maintenance.
Differences between autoflowering and photoperiod strains
Growth cycle and timeframes
One of the reasons why autoflowering cannabis plants are so popular and loved by so many cultivators, is down to the fact that they will flower after 4 weeks of vegetation without the need to provide 12 hours of darkness. This means you can germinate your autoflowering cannabis seeds into a pot and leave it under 18–20 hours of light indoors, before harvesting 9–10 weeks later.
Photoperiods, on the other hand, require a long vegetation period, under 18 hours of light and 6 hours of darkness. Once an indoor grower switches their timer to 12 hours of light and12 hours of dark to induce flowering, photoperiod cannabis plants will enter a transition and stretching phase that will last for 2 weeks. Flowering time afterwards will vary depending on the genetics and will range between 8–12 weeks flowering in most cases.
Sensitivity to nutrients and environmental conditions
Autos have a much shorter life span than photoperiods, especially when planted outdoors. Not only can autos be grown indoors under any light cycle, but they are also much more resilient to environmental conditions and only need a light amount of nutrients from seed to harvest. As long as the temperature and humidity levels remain consistent, very little plant maintenance is required.
Photoperiods will need much more tender loving care from seed to harvest and will depend on the grower to apply the correct nutrients throughout the seedling stage, vegetation stage, flowering stage, and pre-harvest stage.
Key soil characteristics for autoflowers
If you are a first-time grower and like the challenge of working with resilient, easy to grow and low maintenance autoflowering plants, then below are the different key soil characteristics you should be aware of, when deciding the best growing medium to work with.
Drainage and aeration
Ensuring you have the optimal level of drainage and aeration, will allow the plant’s roots to remain in an oxygen-rich environment, with the ideal amount of moisture and nutrient uptake and availability. Watering autoflowering plants frequently is essential for any successful grower, so making sure the soil has the correct drainage and aeration is key.
Nutrient composition and organic matter content
Autoflowering cannabis plants will require nitrogen, phosphorus, and potassium as their primary nutrients, as well as calcium and magnesium as secondary nutrients. Combined with trace elements and minerals will provide the full spectrum of nutrients for the best yields and quality buds.
Soil naturally contains millions of beneficial microorganisms, probiotic bacteria, humic, fulvic and amino acids. As organic matter breaks down, autos will have access to a wide range of nutrition and everything they need to thrive from seed to harvest, so the correct nutrient composition and organic matter content plays a major role when it comes to autoflowering cannabis plants.
pH level considerations
Primary and secondary nutrients as well as trace elements are all accessible within a set pH range between 6.0–7.0. pH level considerations are an essential part of ensuring optimal nutrient uptake and availability when growing autos and preventing nutrient deficiencies.
Components of an ideal soil mix for autoflowers
All you need to do when creating the ideal soil mix for autoflowers, is to have a full awareness of drainage, aeration, wicking ability, the correct pH levels, beneficial microorganisms and bacteria, and enough nutrition to last from the day you germinate until the time to harvest.
Base materials
To guarantee you are on the road to success, you can always mix other growing mediums to achieve the most desirable soil quality possible. Below are the different mediums that should be used when starting out with the best soil for growing autoflowering cannabis plants.
Organic potting mix:
There are many brands of soil available from cannabis brands, or at your local garden centre. Our tip is to avoid cheap soils and make sure the soil composition has good drainage, full of organic matter and contains a fresh and earthy aroma and texture.
Coco coir:
Made from the hairs from coconut husks, coco coir may be an inert growing medium (contains no nutrients), however, when mixed with soil, provides an incredible amount of aeration and holds a high volume of water.
Peat moss:
Mined from peat bogs, peat moss is an excellent way to regulate the acidic profile in the soil, making it ideal for growing cannabis. When mixed evenly with soil and coco coir, the plant’s roots will thrive inside the oxygen-rich soil structure and prevent soil from becoming compact.
Soil amendments
Perlite and vermiculite:
A low-cost soil amendment that significantly improves the soil structure, aeration, and drainage quality. When making custom soil, adding 30% of perlite and vermiculite together will prevent over watering and provide plenty of fresh air and oxygen for the roots to grow inside.
Worm castings:
Produced by worms and teaming with millions of beneficial bacteria and microorganisms, worm castings are a wonderful soil amendment. Not only will it provide nutrients and trace elements for long time frames, but it will also encourage the soil food web to thrive.
Compost:
Adding compost to your custom soil mix provides a high organic content, slow release of calcium and magnesium, high levels of carbon for the microbes present, and overall, dramatically increase soil fertility and soil structure.
Bone meal and blood meal:
If you are looking for a natural source of nitrogen and phosphorus to provide your autoflowering cannabis plants, then bone meal and blood meal will be an excellent choice. However, be careful when planting autos outdoors, as flies are often attracted to bone meal.
Kelp meal:
Trace elements are an essential part for promoting plant growth, and using kelp meal will ensure your autoflowering soil mix will never run short and promote a healthy soil food web.
Crafting your own super soil for autoflowers
Now you are aware of the base materials and soil amendments to use, all you need to do now to create a super soil for autoflowering cannabis, is focus on the correct balance when mixing. Super soil will deliver the best flavours, aromas and cup winning quality buds come harvest time.
Step-by-step guide to mixing soil
Using a measuring cup and aiming for an even amount of base materials and organic amendments will be the easiest way to crafting your super soil. Aim for a texture that feels airy, spongy, and contains an earthy aroma to create the ultimate levels of aeration, drainage and long-lasting nutrition. Below are the different percentage ratios you can use as a guide to make the ultimate super soil for growing autoflowering cannabis plants.
● Organic Potting Soil =20%
● Coco Coir = 15%
● Peat Moss = 15%
● Perlite and Vermiculite = 30%
● Worm Castings = 5%
● Compost = 5%
● Bone and Blood Meal = 5%
● Kelp Meal = 5%
Using pre-made soils
We would recommend to using freshly made super soil for achieving great results. The pros will be there are high amounts of available nutrients, organic content, top quality aeration, drainage, water retention and pest free.
The cons will be they can be more expensive than commercial bought soils to create, take time and effort to measure out and mix, and the ingredients need picking up from grow shops or need to be delivered to your home.
This does not mean that soil from your local garden centre will be a bad choice, so our advice is to choose a chemical free soil, avoid old soil that has been sat around for long periods of time, and soil that has been exposed to sunlight.
The pros are commercial soil is cheap, easy to source and will often times be made by local producers. The cons are it can often times be old and lifeless, contain insects and have been sat in a cold or hot environment for long periods of time.
Best practices for soil management during the grow cycle
Managing your soil when growing autoflowering cannabis from seed until harvest will be the difference between being a good grower and a great grower. Below are the different factors that should be considered.
Monitoring and adjusting soil pH
The easiest way to monitor the pH of your soil is to use a pH meter that can be inserted into the top of the pots and will show you the exact pH level. You can also collect the run-off from the pots after watering using a cup and insert a digital pH pen to gauge the difference in pH over time.
Peat moss contains a pH level ranging between 3.0–4.0 so using peat moss as a top dressing or making a cold-water extract then watering is one way to lower pH if necessary. Compost has a pH level between 6.0–8.0 so can be used in the same way to help increase pH levels if required.
Watering strategies
When working with a custom super soil, all you need to do is add water. How often you water should be based on how wet or dry the medium has become. You do not want the soil to become oversaturated, as the roots will be starved of oxygen.
The risk of soil pathogens will be significantly increased, and the plants will wilt downwards and slow down growing. If the growing medium becomes too dry, nutrients will not be accessible, and the plants will become hungry and show signs of nutrient deficiencies.
The best way to manage the right amount of water is to use a measuring jug and aim for a consistent watering schedule every 24 or 48 hours. When growing autoflowering cannabis, and make sure your pots are draining well enough to produce a small volume of run off at the base after every watering cycle.
Nutrient management
Top dressing in an excellent and highly practical way to ensure your autoflowering cannabis plants have more than enough nutrients during their lifecycle. Using a 0.5-liter cup to measure, use worm castings, compost, bone and blood meal, and kelp meal mixed together and apply a centremeter high layer to the surface every 2–3 weeks to create the perfect form of nutrient management.
