Can You Grow Plants In Compost Only?

Compost is one of the best things to add to your garden because it provides texture, nutrients, and beneficial organisms. But could you grow plants in compost alone?

You cannot grow plants in compost only because the material is too light and will cause the water to drain too fast. The soft and crumbly texture will not provide good support to the plant’s roots and cause it to topple over. The compost can lead to excess nutrients making it toxic for the plants.

I’ve written details below on why you should not use compost alone in your garden. I’ve also mentioned the best way to use compost in your garden and its benefits.

Compost will dry out fast

The biggest issue with using only compost to grow your plant is the light and crumbly texture. This will cause the water to drain out fast and your plant to dry out quicker.

If you mix in some soil together with the compost, the texture will be better and your plants will not dry out as fast.

If the soil contains too much sand, the water will drain out fast. If the soil contains too much clay, it will hold the moisture for longer.

When you mix compost with such soil, it helps improve the texture and the water-holding capacity. This makes it easier for it to hold the moisture for the required time and not too long.

Compost tends to be expensive

The compost tends to be expensive, especially when you buy it at a store. You can save some money if you make it yourself, but it will cost you time and effort.

That’s why it’s best not to only use compost to grow plants because you’ll need to either make or purchase a lot of it. 

You should mix topsoil with a few inches of compost to help you save money and get the best texture for the soil. Compost is best for improving the soil texture, but topsoil is more beneficial to plants in terms of structure and water retention.

Compost will not provide stable support

The texture of compost is soft and crumbly. If you try to grow plants directly in the compost, the roots don’t get the required support.

When the plant grows to a bigger size, the compost won’t be able to support the plant. There is a risk that the plant will fall down as a result.

It’s best to mix soil with the compost so the roots and the base of the plant can get the required support.

Compost will compact quickly

The soft and crumbly texture of the compost means that it will compact very fast. The more water you add to the compost, the more it will start to shrink.

This is a problem because the compaction will reduce the pores in the soil and the roots will struggle to get access to air. The roots also won’t be able to get nutrients and moisture from the compost.

The compact texture also means there will be water collecting in the compost. This will cause the roots to drown and lead to fungal diseases and root rot.

If you add soil to the compost, you won’t face this problem. The texture will be just right so the soil can retain sufficient moisture but drain out the excess. The soil won’t compact after you give it good watering.

Compost will lead to excess nutrients

One of the benefits of compost is it can add a lot of beneficial nutrients to your soil. This includes macronutrients like nitrogen, potassium, and phosphorus.

It also includes micronutrients like calcium, iron, boron, magnesium, manganese, sodium, and zinc.

If you grow the plant only in compost, there is a risk that the nutrients are more than what the plant needs. This excess will cause toxic buildup in the soil.

This can end up killing the plant or causing problems such as yellowing foliage, blooms, or damaged fruit.

Mixing the compost with soil will give the right balance of nutrients to the plant. This will help the plant develop healthy roots, foliage, flowers, and fruits.

How to add compost to your garden?

Now that you know it’s not good to only use compost to grow your plants, I’ll show you how to mix compost with soil and use it for your plants.

The simplest way to use compost is to add 2-4 inches of compost to your garden bed. You can place it on top of the bed and mix it in with a rake.

You should add compost to your soil depending on the area of your garden. If you have a 40-foot by 100-foot area, you can add 4,000 cubic feet of compost.

If you are growing the plant in a container, you can add 25% compost to the potting soil when preparing it.

Once the plant has matured, you can add a 1-2 inch layer of compost every month or two to the soil and mix it in with a rake. This will help the soil get a consistent supply of nutrients as the plant is growing.

Can you start seeds in compost?

If you start seeds indoors, you just need a little bit of soil for your seed-starting tray or container. I would not suggest using compost to start your seeds because the excess nutrients can burn the roots.

The seeds have all the required nutrients till they time they germinate and develop their first leaves. So you don’t need to provide them with additional nutrients during this growth phase.

It’s much better to use a sterile potting mix that does not contain any nutrients and is free from any pathogens.