compost fertilizer soilless mixes

(Part 3) Compost vs. Fertilizer: 6 Ingredients for Easy Soilless Mixes

The 6 Ingredients of a Soilless Mix, Part 3: Compost vs. Fertilizer

Most soil mixes for a container plant contain little to no soil at all, which is why they are called soilless mixtures. They are usually comprised of a combination of organic matter, like peat moss, and inorganic material, like perlite or vermiculite. Indoor plants can thrive in actual soil from your backyard – just make sure you know what your plant needs and what type of soil you have!

Many of the ingredients for these soil mixes can be confusing for a first time DIY-er, so I’ve compiled a short list of the main components and how they differ. For this third (and final) installment, I compare the advantages and disadvantages of compost and fertilizer so you can decide which is best for you and your plants.

soilless mix
ingredients for a soilless mix

Compost vs. Fertilizer

While some may say that compost and fertilizer are interchangeable additives for your soilless mix, they are not. Even though both help create a healthy growing environment for your plants, each provides nutrients in different ways. Compost – also called ‘black gold’ – is organic, and you can either make or buy your own. Though fertilizers can be quick fixes to feed your plants, some contain synthetic chemicals.


Compost is a dark, crumbly form of decomposed organic matter. Most plant material – such as fallen leaves, pine needles, and the remains of your annual herbs – can be used for compost, as long as it has not been treated with herbicides or pesticides. You can also add all of your food waste to your compost– including, but not limited to, fruits and vegetables, eggshells, coffee grounds and filters, tea bags, nut shells, shredded newspaper, dryer and vacuum lint.

However, do not compost dairy products and eggs; fats, grease, lards, or oils; meat or fish bones or scraps; or pet wastes. These materials can create odor problems and attract pests like rodents or flies. In more serious cases, they might contain parasites, bacteria, and germs that are harmful to you and the soilless mix you are creating.

  • Advantages
    • Enhances the nutrients and microbes within the soil
    • Retains water and nutrients
    • Helps aerate the soil while also keeping it moist
    • Loosens dense, compact soils – like clay – when added
    • If you create your own, you’re recycling your food waste and lowering your carbon footprint!
  • Disadvantages
    • Potential for soil-borne pathogens to infest, damage, and kill healthy plants
      • Lix’s Pro Tip: When creating your own compost, destroy any plant remnants that could be infested with disease instead of adding them 

There are two types – organic and inorganic (aka, chemical) – that provide your plants with key nutrients that the soil may lack. These nutrients are separated into three categories: primary, secondary, and micronutrients. Primary nutrients are nitrogen (N), phosphorus (P), and potassium (K); they are needed in large quantities compared to the other two categories of nutrients. Calcium (Ca), magnesium (Mg), and sulfur (S) are considered secondary nutrients, but are still incredibly essential for your plant’s health. Micronutrients include zinc (Zn), manganese (Mn), iron Fe), boron (B), copper (Cu), molybdenum (Mo), and chlorine (Cl), and your plant requires these in very small amounts.

Some organic solutions feed the soil and the plant. They tend to be slow-release and feed your plants over time; however, sometimes they may not release enough of the nutrients at a time to give your plant what it needs to grow.

Inorganic/chemical fertilizers tend to be more cost effective and composed of the primary nutrients in forms that are easily utilized by your plant. However, because the nitrogen is in such a soluble form, it tends to leach (aka the loss of water-soluble plant nutrients from the soil, due to rain or irrigation) from the point of application. Moreover, water-soluble chemical fertilizers tend to injure plants if not properly applied or rinsed off from the leaves.

  • Advantages
    • Targets specific plant nutrient deficiencies
    • Can be a quick fix
      • There are slow-release formulas that will feed your plants over time
    • Disadvantages
In conclusion…
  • Use compost if you want to feed your soil
  • Use fertilizer if you want to feed your plants

Images of Compost & Fertilizer Usage