Potting Soil Mix for Flowers – Preparation Method

Introduction: Hello flower gardeners would you like to prepare and apply your own potting soil mix for flowers, let us do it. Soil mix can hold moisture and nutrients for plants to take up whenever they need it, so they don’t require constant watering and fertilizing. And while keeping the pH level of the nutrient solution in the recommended range is always important, the range is wider for the soil than in hydro and soil is more forgiving when the solution falls slightly out of the range.

A guide to prparing and applying potting soil mix for flowers

Standard potting soil is normally comprised of three things;

  • Composted tree bark
  • Sphagnum peat moss
  • Vermiculite or perlite

While there can be many more ingredients, these are the base three that make up the bulk of most potting soil mixes. These three ingredients are meant to hold nutrients and moisture while still giving plants plenty of air.

Different things make a good potting soil


Quality potting soil will have all of the nutrients that your flower plants need to thrive. They will include humus, finished compost, or gypsum and other ingredients to ensure optimal nutrition.


High-quality potting soil mix will be light, fluffy, and not compact easily. It will allow the roots to access air and oxygen so they can increase optimally.​

Moisture Retention

While aeration is very important, the best potting soils must balance aeration with water retention. They require to drain well to avoid mold or rot but hold on to some moisture so your plant’s roots can drink.​


Good potting soil mix will have a consistency that makes it easy for plants to anchor their roots. It provides stability for a flower plant’s root system, preventing them from falling over or being torn out by the wind.

Slow Release

If a potting soil mix says that it has “slow-release” fertilizer, this means that it contains slightly more fertilizer, but only enough for approximately a month. Again, you will have to eventually add own fertilizer, but the slow release will last for at least a few weeks.

Maintaining Moisture

In addition to fertilizer, many potting soils will contain added chemicals or ingredients that are meant to help retain moisture. This is a great feature, and it allows you to water your flower plants a little less often than normal. You still will need to keep an eye on everything and make sure that you do not leave the garden for too long, but it does give you some breathing space.

An important thing to keep in mind with potting soil that has water-retaining features is that you should avoid overwatering. Because the soil holds more water than normal, you will have to make sure that normal watering patterns do not leave it too saturated.

Potting soil mix needs to drain well but still hold moisture

One of the most important things a potting soil mix needs to do is provide roots access to the air by letting water drain away from them. In the ground, the soil is generally deep enough to let the excess water drain beyond root zones. In pots, water tends to accumulate at the bottom, despite drainage holes. The smaller the pore spaces of the soil in the pot or container, the higher that water layer will reach. Larger pores, formed by adding mineral aggregates to potting soils, readily admit water into the soil and then carry it through the medium and out the bottom. Then, all those very large, empty spaces can fill with air.

Perlite, vermiculite, calcined clay or kitty litter, and sand are the mineral aggregates most commonly used in potting soils. Prefer perlite over the others because it does not decompose with time nor lose its aerating ability if the potting soil mix is compressed. Vermiculite is a valuable additive as it prevents some nutrients from leaching away, and it even provides a bit of potassium and magnesium. In addition to peat moss, vermiculite, and perlite, commercial mixes often have sawdust or various grades of shredded bark. Lime can be added to help balance the acidity of the peat moss and a small dose of fertilizer can often make up for the lack of nutrients.

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The formula of potting soil mix for flowers

Formula for Potting Soil Mix.
Formula for Potting Soil Mix.

To create your own perfect potting soil mix, thoroughly blend 1 part peat or coir, 1 part perlite or vermiculite, one-half part composted bark, and one-half part worm castings. You can grow just your flower indoor garden with this mix. After each grows cycle, dump the contents of each container and begin with a fresh mix.

Qualities of a good mix – Poor performance in a potting soil mix is costly since greenhouse space is expensive and so is having to toss out some seedlings or replant entirely. Optimal mix characteristics include the right density and porosity to give good aeration and also good water holding capacity; proper pH level and enough available nutrients to get plants off to a good start, and the absence of excess salts and plant pathogens.

Common potting soil mix ingredients

  • Sphagnum peat moss is a stable organic material that holds 15 to 30 times its weight in water and decomposes slowly. It contains about 1% Nitrogen but little is released because it breaks down so slowly. It has a pH of about 4 so lime should be added to the mix to along with sphagnum peat, at the rate of 8.5 lb. per cubic yard of peat to neutralize the acidity.
  • Peat moss is a dead fibrous material that forms when mosses and other living material decompose in peat bogs. Peat moss is an excellent soil amendment for acid-loving plants. Peat moss is also known as a dead fibrous material of sphagnum species, forms when moss and other living materials become decomposed in peat bogs. Peat moss has a low pH level, so if you use much, lime should be added as well. Plants that do well in acidic soils, termed “ericaceous” such as blueberries and rhododendrons, advantage from peat moss.  Compost generally has a neutral (pH 7) or slightly alkaline soil reaction.
  • Coir mainly comes from coconut husks and is a waste product of the coco fiber industry. It has physical properties much like peat but a higher pH level of about 6. It holds up to 9 times its weight in water. Coir can have a high salt content.
  • Limestone is calcitic (high calcium) or dolomitic (high magnesium). Both are used to increase the pH level of a soil mix but dolomite is preferable for supplying both Ca and Mg.
  • Vermiculite helps hold water and fertilizer in the potting soil mix, and it also contains some calcium and magnesium. It has a pH level near neutral. Vermiculite comes in different grades; the medium grade is generally used for starting seeds, a coarse grade may be used for larger plants.
  • Perlite is a volcanic rock that has been heated and then expanded. Perlite is lightweight, sterile and has a neutral pH. It can be used to improve reduce the weight of a potting soil mix and increase its aeration and drainage. Perlite and Vermiculite are both volcanic in origin and both are put into the potting mix to give additional air space and to lighten things up so a potting mix is not too dense and heavy. Perlite does not give any nutritional benefit and can collect fluoride if water containing it.
  • Coarse washed sand also called the builder’s sand can be used to add air space to the potting soil mix and increase its weight. It has a neutral pH level and provides almost no fertility to plants. Sand can be used when added weight is needed for growing tall or top-heavy plants that might fall over if grown in a lightweight mix.

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Main functions of a potting soil mix for flowers

Potting soil is also called as potting compost or potting mix. It’s a medium in which you can grow flowers in a pot or a container.

Functions of Potting Soil Mix.
Functions of Potting Soil Mix.
  • To hold moisture and nutrients around your flower plants roots, acting as a reservoir for these critical elements of life in your container garden.
  • Potting soil provides enough air for growing roots to be able to breathe and not rot once you plant your container. Most people don’t think about this, but it is critical to have a good amount of air in the garden soil. Not enough and generally the plant roots have a hard time surviving.
  • To support your flower plant, providing anchorage for the roots. A soil mix needs to settle around the roots of the plant and help hold it in place so that it doesn’t blow over from the first wind. However, it needs to be light enough to allow water and air to always be present under the soil surface so your plant’s roots have a balanced atmosphere to grow in.

Rules for choosing a potting soil mix for flowers

  • Potting soil used in containers must be light and fluffy.
  • Look for a potting soil mix made up of peat moss, pine bark, and perlite or vermiculite
  • Fertilizer can be added in the form of a “starter charge” or slow-release formulation. Adjust fertilization practices accordingly.
  • Potting soil may use moisture-retaining treatments, watering patterns may require to be altered if you use a potting soil containing these substances.

Fungal growth on potting soil mix 

Most prepared potting soils that are bagged and sold at garden centers and home supply stores have been prepared months in advance of the actual sale. Generally, these mixed soils are composed, sterilized or at least heat-treated to eliminate any diseases, weed seeds and other pathogens that could ultimately impact what you are going to pot and grow in the soil. When you use the mix, you are exposing that sterile soil to a huge assortment of native fungi spores that are ambient in the home and garden.

The sterile soil is a perfect home for these fungi or mildews since there is no competition for the organic material that makes up the soil mix. These fungi grow fast, particularly when given the ideal growing conditions. Under normal outdoor growing conditions, the fungi are generally short-lived. Drying the potting soil mix out, exposure to sunlight and simply being exposed to other competitive organisms, the mildew disappears through rapid attrition.

Homemade potting soil mix for flowers

Potting soil is different than soilless potting mix; the latter is used to germinate seeds. The best homemade potting mixes have three ingredients they are growing medium, something to help retain moisture and nutrients, and something to promote drainage.

There are several recipes to make homemade potting soil mix. To closely mimic pre-packaged potting soil, you will need;

Growing medium – Garden soil from a home center, this is pre-sterilized to remove weeds or disease.

Moisture retention – Spaghnum peat moss. It is harvested from bogs that have been drained, so the peat moss has dried and turned a light brown color; you may need to lightly moisten before mixing the potting soil.

Drainage – Perlite, vermiculite, or sand. Perlite is normally made by heating bits of a glasslike mineral until it expands into puffy, lightweight particles. And it holds no water, aside from the little that clings to the surface of each particle.

Mix those three ingredients in equal proportions, adding more of any ingredients until you have a loose, but clump-able, mix.

How to Choose the best potting soil mix for flowers

Most people generally prefer using organic soil for their plants. In most cases, this is because organic soil doesn’t have genetically engineered pesticides and chemicals. Organic material is more beneficial than regular soil. In this potting soil mix, natural materials ensure that your plants will be provided with the nutrients they need to flourish.

You can also consider to read the Preparing Soil for Vegetable Garden.

How to Choose Best Potting Soil.
How to Choose Best Potting Soil.

Different organic soil mixes will have different ingredients. Some of the common ingredients are compost, seaweed, soybean meal, humus, mushroom compost, fish meal, bat guano, and bone meal.

Depending on the plant you want to grow, the exact potting mix you must use will vary. Therefore, using the proper organic potting soil will ensure that your flower plants will grow naturally and that their rooting systems will be healthy.

On the other hand, non-organic soil doesn’t have any organic matter. And, you won’t find any common ingredients that are used in natural soil mixes. This soil is something that people like to call “regular potting mix,” and it’s a combination of bark, peat moss, and perlite or vermiculite. You will get these ingredients in most of the non-organic potting mixes, but different products will have different combinations, and some will even have extra nutrients and minerals.

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