Best Potting Soil for Weed Indoors

Photo of author
Written By Rocky Horton

This post may include links to our partners. Learn more. 

Choosing the best potting soil for weed is absolutely crucial for a great grow. With so many options out there, it can be hard to know which soil is best.

In this article, we’ll explore the best options to nurture your plants and maximize your yield. Let’s dig in and find the best soil for your indoor cannabis grow!

What to Look for in a Good Cannabis Soil?

The ideal cannabis soil should be light and airy, with a good drainage system. It should be rich in organic matter and have a slightly acidic pH. The soil should also be loose and crumbly, so that roots can easily penetrate it.

Cannabis plants do best in sandy loam soils but can also grow in clay or loam soils that have been amended with organic matter. Good cannabis soil should also be high in nutrients, especially nitrogen, phosphorus, and potassium. Cannabis plants require good air circulation to prevent fungus and other pests from developing, so a well-drained soil is also essential.


The best soil texture for growing cannabis indoors is loose and well-aerated, allowing the roots to penetrate the soil and access nutrients easily. Loamy texture includes an optimum mixture of silt, sand, and clay soil. Ideally, the mix should have about 40% silt, 20% sand, and 40% clay.

Soil that is excessively compacted can impede root growth and lead to nutrient deficiencies. Make sure your plants are grown in a loose and light soil to help with root growth and ensure oxygen gets to your roots.


To avoid water logging, soil drainage is one of the most critical factors in good cannabis soil. If the soil does not drain well, the plant’s roots will not be able to get the oxygen they need, and the plant will suffocate.

The plant will also be more susceptible to root rot and other problems. Good cannabis soil should be light and fluffy and drain well.

Water Retention

Soils with good water retention capacity can ensure that your plants have a consistent supply of water, which is essential for healthy growth. If your soil does not retain moisture well, your plants will be susceptible to drought conditions and may not grow as vigorously. Additionally, water retention helps to regulate the temperature of your soil, which is vital for preventing heat stress in your plants.

Many factors can affect water retention in soil, including clay, organic matter, and soil porosity. When choosing soil for indoor cannabis cultivation, selecting one with a good water retention capacity is crucial to help ensure consistent yields. Testing the soil’s water retention capacity is an excellent way to determine if it is appropriate for your specific grow setup.


The ideal pH range for cannabis plants is between 5.5 and 6.5. You can use a soil test kit to test the pH of your soil and adjust it accordingly. If you are growing cannabis in coco coir, the ideal pH range is between 5.5 and 6 .8.

If your soil’s pH is too high, it can cause excess water uptake and plant stress. If your soil’s pH is too low, it can lead to nutrient deficiencies and stunted plant growth. Testing the pH of your soil is a simple way to ensure that you provide your cannabis plants with the best possible environment to grow.


Nutrients are essential for several reasons. They help the plant to grow and develop properly, they help the plant to resist pests and diseases, and they help the plant produce high-quality buds. A good cannabis soil will have a balanced nutrient content that will provide the plant with everything it needs to grow and thrive.

Some of the essential nutrients for cannabis plants are nitrogen, phosphorus, potassium, magnesium, and calcium. Each of these nutrients plays a role in the plant’s growth and development.
• Nitrogen is essential for the growth of roots and stems.
• Phosphorus helps the plant to build protein cells.
• Potassium helps the plant to create energy from food sources.
• Magnesium helps the plant to produce chlorophyll and other organic compounds.

Organic vs Synthetic Cannabis Soil

Cannabis soil can be either organic or synthetic. Organic cannabis soil is made from natural materials like compost and manure, while synthetic cannabis soil is made from artificial ingredients like chemicals and artificial fertilizers. Both types of soil can be used to grow cannabis, but there are some key differences between them.

The most popular premixed (nutrients added) soils for cannabis are FoxFarm Ocean Forest and Happy Frog. Both of these are considered organic soils and are great choices for growing cannabis.

You also have the option to use an organic base soil mix such as ProMix HP and add your own organic nutrients such as the Gai Gai blend or the Craft Blend from BuildaSoil. You may also want to add worm castings and possibly bat guano to the mix.

Note that organic soil is not necessarily “living” soil. Living soil is often composted for an extended period of time to allow the microorganisms to colonize and break down the organic matter.

Peat Moss

Peat moss is a type of moss that is commonly used as a soil amendment or as a mulch. It is spongy and absorbs water well, making it suitable for plant growth. Peat moss is also acidic, so it can be used to lower the pH of soil.

Peat moss is an excellent source of organic matter and helps improve drainage and aeration in the soil. Peat moss also helps to hold moisture in the ground, making it an ideal amendment for sandy or clay soils.

Sphagnum peat moss is the most popular variety of peat moss and is widely available in garden centers and nurseries. Sphagnum moss is often used in potting mixes and as a seed starter.

Peat moss is also available in rolls or pellets that can be easily stored in a cool, dry location. Peat moss has a long life and can be recycled multiple times. It is also a renewable resource.

Common Soil Additives or Amendments

Most often, when people talk about soil additives or amendments, they refer to products you can use to improve soil quality. A soil amendment is any material added to soil to improve its physical properties. They aerate the soil, allowing water and nutrients to circulate more easily and reach plant roots. Some soil additions also add nutrients to the soil, aid in moisture retention, and help maintain the proper pH balance.

Amendments can be organic, like compost or manure, or inorganic, like limestone or gypsum. Most indoor cannabis growers use some soil amendment to improve the quality of their grow medium and provide nutrients for their plants. If you are looking for soil additives or amendments that will help with indoor cannabis growing, check out some of our top picks below!


Perlite is most commonly used as a soil amendment because of its high water retention and porosity. Perlite is a lightweight, volcanic rock heated to a high temperature until it pops like popcorn. The resulting particles are white and have a porous, spongy texture. Perlite can absorb up to four times its weight in water, making it an ideal amendment for soils that need help retaining moisture.

Add 10-15% perlite to your soil to improve it. You can add more, but your soil will become too light, and nutrients will drain. Perlite is frequently added to high-quality commercial soils.

When perlite is added to soil, it helps to keep the soil moist and improve drainage. Additionally, perlite helps to aerate the soil and reduce compaction.

Coco Coir

Coco coir is a soil amendment made from the husks of coconuts. It is an organic material that is environmentally friendly and sustainable. Coco coir is an excellent alternative to peat moss and other soil amendments.

It has a high water holding capacity and is excellent at aerating and drainage. Coco coir also has a high cation-exchange ability, which means it can hold onto nutrients and make them available to plants. Cannabis plants grown in coco coir soil tend to be taller and stronger than those grown in soil without coco coir.

Some grow their cannabis in a pure coco substrate with specific nutrients. However, depending on the makeup of your base soil, adding up to 30% coco coir to existing soil is an excellent idea.

Coco coir is a good choice for cannabis growers looking for an organic amendment that can help improve the quality of their soil. It is also a good option for those who want to avoid using synthetic fertilizers or pesticides. Coco coir can be used in both indoor and outdoor cannabis gardens.

Bat Guano

Bat guano is a soil amendment that can be used in cannabis soil. It is rich in nitrogen and phosphorus, which can help to improve plant growth. Bat guano can also help improve the soil’s drainage and aeration. Additionally, it can help to increase the amount of organic matter in the soil.

Bat guano is available in powder or pellet form and can be applied to the soil before planting or during the growing season. When using bat guano, it is vital to ensure that the soil is wet before adding the amendment, as it will not activate if it is dry. Growers should use it in conjunction with other soil amendments and fertilizers for it to work more effectively.

Worm Castings

Worm castings are made from the excrement of earthworms. They are an excellent source of nutrients and organic matter for plants. Worm castings can help improve the quality of your cannabis soil and can also help increase yields. They are a natural and organic way to amend your soil and are safe for humans and the environment.

Worm castings can also help to aerate the soil and improve its drainage. In addition, they can help to control the growth of fungi and bacteria in the soil.

Growers should apply them on time and at a rate appropriate for the soil amendment’s size. Worm castings can help to improve the growth of cannabis plants, but growers should not use them in place of regular fertilization.

Homemade Soil for Cannabis

It usually involves starting with a base of 70-80% peat moss based on individual preference. It is critical to select the best base soil for your cannabis plants. Remember that cannabis prefers well-aerated, porous, and somewhat acidic soil.

Choose an organic soil with natural materials such as worm castings, compost, coco coir, sand, and others if possible. While these soils are often more expensive, they will significantly improve the health of your plants as well as the quality and quantity of your harvest.

Add 20% perlite or 15% each of perlite and Coco Coir to the peat moss since they’re essential in improving the physical properties of your cannabis soil. Then add a POWDERED SLOW-RELEASE 4-4-4 all-purpose fertilizer. You can optionally add worm castings and bat guano as well to the mix if not already included. You will need to top dress every 3-4 weeks with these same powdered amendments.

You can also use the same method above, but use only peat moss, perlite, and coco coir for the soil and add LIQUID FAST-RELEASE synthetic nutrients throughout the grow.

Premade Soil for Cannabis

Premade soil for cannabis is an excellent option for those looking for a quick and easy way to start growing their plants. This type of soil is typically made with a mix of organic matter and nutrients, making it ideal for cannabis plants.

Also, premade soil is often pre-fertilized, which can help your plants get the nutrients they need to grow quickly and healthily. Because of its convenience and benefits, premade soil is a popular choice among cannabis growers. Premade soil is an excellent option if you want to grow cannabis.

FoxFarm Happy Frog

FoxFarm Happy Frog is a premium potting soil used to grow cannabis indoors. This soil is made from a blend of organic ingredients that give your plants the nutrients they need to thrive.

Happy Frog is also enhanced with mycorrhizae, a beneficial fungus that helps roots absorb nutrients and water more efficiently. It is also pH-adjusted soil to facilitate the utmost nutrient intake. This soil is also aerated and drained well, which helps to promote healthy root growth.

This soil is perfect for growing cannabis in containers, and it will help your plants produce healthy, vibrant flowers. When growing cannabis with Happy Frog potting soil, you can be sure that your plants will receive the best possible care.
FoxFarm Happy Frog works best when used on plants that are already established.

FoxFarm Ocean Forest

The FoxFarm Ocean Forest garden potting soil mix is great for cannabis plants. Each pack contains all that your marijuana plant requires for healthy germination. It comprises earthworm castings, sea-going fish and crab meals, moss, bat guano, forest humus, and other ingredients. All of these imitate the qualities of the best naturally occurring soils.

The soil mix also has sandy loam, indicating clay and silt. The soil mix enables good water drainage with this particular composition. To achieve adequate germination, ensure it reaches all portions of the soil.

This soil is wonderful since it has been pH corrected to be between 6.3 and 6.8. This means that the soil allows for maximal fertilizer uptake. This also promotes vigorous branching, which leads to healthy and quick growth.

FoxFarm Coco Loco

As the name implies, Fox Farm’s Coco Loco formula primarily comprises the inert medium coco coir. Unlike regular potting soil, coco coir contains only trace amounts of potassium. Coco coir is sometimes regarded as a “stepping stone” medium for growers shifting from soil to hydroponics.

While not every grower prefers coco coir, it has various advantages, such as moisture retention and pest resistance. Furthermore, nutrient deficiencies are less likely because Fox Farm’s Coco Loco contains substances such as kelp, bat guano, and earthworm castings.

With Coco Loco, you get the advantage of growing in coco coir without needing to change your feeding plan significantly. You may need to adjust your watering schedule, especially if you don’t use perlite, which aids in aeration and allows more oxygen to reach the roots. Because coco coir maintains moisture better than other mediums, avoid the temptation to overwater!

Roots Organics Original

Roots Organics is a potting soil suitable for fast-growing plants that demand attention and care. Because of its excellent water retention, it is the finest choice for cannabis.

The mixture contains perlite and coco fiber, two of the most critical components for plant growth. It also contains pumice, peat moss, and composted forest stuff; these compounds improve water retention and decrease the need to water the plant. The soil includes coco coir, perlite, vermiculite, and composted chicken manure.

Roots Organics is also a living soil. It contains living mycorrhizal fungus, Funneliformis mosseae, and Rhizophagus intraradices that improve the ability of your plant’s roots to absorb water.

This organic potting soil differs from others in that it is ready to use right out of the bag. Simply cut the bag’s top and plant your seeds. You might even put the ingredients in a container garden.


When growing weed indoors, it is vital to use the best soil possible to achieve the best results. Indoor cannabis grows operations must be carefully monitored and managed to produce the best possible output. The soil you use can make a big difference in the quality of your weed.

A few things to consider when choosing the best soil for weed indoors exist. The first is the pH level. The ideal pH level for cannabis is between 5.5 and 6.0. The soil also needs to be well-drained since marijuana plants are susceptible to root rot and other problems when the soil is wet. Lastly, the soil must have good aeration. Poor air circulation can lead to over-fertilization and respiratory issues for your plants.

There are a few types of soil that are ideal for cannabis cultivation. You can buy premade soil from garden stores or prepare your cannabis soil with the necessary ingredients. You can further improve the physical properties of your cannabis soil using amendments.

Weed needs the best soil to grow indoors to get the right amount of nutrients. With the right soil, you can grow healthy and strong weed that will produce great results. If you’re growing marijuana indoors, choose a suitable soil! It will make a massive difference in the quality of your weed.

Rocky Horton Avatar

Rocky Horton


Rocky Horton is an experienced cannabis grower and the founder of IndoGrow. The IndoGrow editorial team has over four decades of combined growing experience. Learn more.