Soils for Growing Marijuana Seedlings

Rambo December 7, 2011 4
Soils for Growing Marijuana Seedlings

Choosing the correct type of soil for germination and marijuana seedlings is a crucial step to growing marijuana and an easy first step to get wrong. This article will explain what you need to know to get your seeds germinated and plants growing strong for the first few weeks.

Before I get started I want to make two things very clear. First, you don’t have to use soil to germinate marijuana seeds; you can use rockwool, coco fiber or a number of other soilless mediums. Here I will only be sharing information on soils. Second, the soils you use to germinate seeds and grow your plants for the first week or two will not be desirable for later in the plant’s growth cycle. You will need to transplant into a soil that contains more nutrients within two weeks.

When choosing the right soil for germinating marijuana seeds, there are three things you need to get correct: pH, nutrients, and drainage.


Marijuana plants thrive in soil with a pH between about 5.5 and 6.5 but struggle when growing in soils outside of that pH range. As the soil gets further from the desired pH range, it becomes difficult, then impossible for marijuana plants to uptake certain important nutrients. This nutrient lockout not only deprives your plants of important nutrients which stall growth but leads to plant stress and eventually plant death. Additionally, a plant not receiving all of the important nutrients has a compromised immune system and is more susceptible to plant diseases and pest infestations.

Nurseries sell many different types of potting soils with a wide range of pH values. Each kind of plant prefers its own pH range, which is why you will see different soils marked for specific kinds of plants like geraniums, roses, and lawns. Make sure you start out with a soil in the pH range between 5.5 and 6.5 and you’ll be starting off in the right directions.


Finding a great soil for germination and marijuana seedlings also requires knowing a bit about the nutrients potting soils contain. The reasons you might choose to use soil in the first place instead of a soilless medium is that the soil already contains some of the important nutrients that your plants require. Regardless of whether you are using an organic or non-organic potting soil, most quality soils will be pre-fertilized.

Remember that your seeds already contain enough energy to sprout and get them through the first week above ground. Marijuana seedlings are delicate at this stage and very susceptible to nutrient burn. It’s best to use potting soils marked as “light” or “lightweight formula,” meaning they contain very low nutrient levels. These “light” soils won’t have enough nutrients for the later stages of plant growth but are ideal before the first transplant.

Look for soils that suggest that you fertilize within the first week and continue to fertilize throughout the plants life as this indicates that the soil contains very low levels of nutrients.


Potting soil ideal for germination and seedlings will be light and loose to allow for excellent drainage while retaining both moisture and air. Because marijuana seedlings require constant and even moisture throughout the soil, it’s not uncommon for even experienced growers to over-water seedlings. A potting soil with good drainage will go a long way to help prevent any problems that a little over-watering may cause.  Look for soils with a fine fluffy consistency that won’t turn to mud when drenched or crust over when they begin to dry out.

  • Don’t use garden soil from outside for starting your seeds or any other kind of indoor growing. Outdoor soil always contains some kind of pests better left outside. While they are kept in check naturally outside, they often thrive inside where temperature and humidity is ideal for rapid growth in pest population and there exists no natural predators.
  • Don’t use potting soils with time-release fertilizers or high NPK values.
  • Don’t use potting soils for germination for seedlings that contain guano. Guano is a super strong fertilizer and can easily burn young plants. 
  • Don’t use potting soils with large amounts of non-composted materials like wood chips
  • Don’t use potting soils with strong harsh smells like sulfur or mold.

VN:F [1.9.22_1171]
Rating: 3.7/5 (67 votes cast)

Soils for Growing Marijuana Seedlings, 3.7 out of 5 based on 67 ratings



  1. Gary's Rig February 9, 2013 at 8:12 pm -

    Good stuff on soil, I am a old time “bio dynamic” farmer, it’s a shame people avoid learning the proper stewardship of taking care of Mother Earth.

    I appreciate how you talk to a level the a novice can follow, I love your style!

    Your Friend

    Uncle Gary Bio-dynamic RIg

  2. Kyle July 9, 2013 at 11:53 am -

    I planted a garden outside! Im germinating MY 15 seeds I planted in a staggered position half an inch in fluffy soil for air unfortunately its in mirecalgrow soil will it be ok

  3. colin Paterson November 5, 2013 at 10:00 am -

    Your. Site. Has learned me almost all I needed to get my 3 plants. Done correctly ESPECALLY My 1st Attempt and both grew amazingly SO I THANK U SO MUCH your website is EASILY 100 oout of 100 THANK U AGAIN + AGAIN+

  4. Felix July 19, 2014 at 2:41 am -

    very easy to understand. it’s been 35 years since i last cultivated. back then i done nothing special. threw ’em in the grown and hit ’em with othogrow and you know k-sir-ra sir-ra. this time i want to get it right. thanks