Horticulture Magazine

All-Purpose Compost

compost and plants in a garden centre

What Is All Purpose Compost?

All-purpose compost is a multi-purpose compost that will suit a wide range of applications in your garden. When people talk about a multi-purpose or all purpose compost, they are usually referring to commercial composts that you can use in your garden in a range of different ways.

These commercial composts are specially formulated with a range of different ingredients. They can provide nutrients, and the right growing environment for a wide range of plants, at all stages of their growth, right through from seed sowing to maturity. All purpose composts can be used as mulch to enrich beds, borders and other growing areas. And can also be suitable for filling planters, containers and pots for houseplants and for an outdoors container garden.

While multi-purpose composts can be purchased, it is also possible to make your own multi-purpose compost at home. The compost that is made in a home composting system could also be an all purpose compost with the addition of some other ingredients such as leaf mold/ shredded wood etc… If you are trying to make your gardening efforts as sustainable and eco-friendly as possible, making your own multi-purpose compost at home can be an excellent idea.

Of course, if you are just starting out, it will take time to establish a successful composting system. So you may well decide to buy in some multi-purpose compost to get started with making new growing areas.

You might also need some to fill containers for houseplants, or for indoors or outdoors small-space food production. Another reason you might buy some multi-purpose compost is to enrich areas of your garden prior to planting or sowing.

Since all purpose composts are ostensibly formulated for use in a huge range of different ways, this means that they can often be a good choice for new gardeners.

It is important to understand, however, that all purpose composts vary significantly in quality. While these composts can often be cheaper than other more specific use composts, results can be variable. Even bags of compost from the same company have been found to vary significantly in quality.

It is also important to recognise that all purpose composts can vary in how eco-friendly and sustainable they are. Their credentials can vary quite considerably in this regard depending on what ingredients are in them. Some come with non-organic and potentially harmful synthetic fertilizers mixed in.

What Is It Made Of?

A general purpose compost is made from biodegraded (or rather partially biodegraded) organic material. But which materials went into making the compost will depend on the formulation of the commercial compost you choose (or what you put into your composting system if you made it yourself.)

Many all purpose compost brands contain peat. But there are other peat-free alternatives to consider, and you should do so. Peat free multi-purpose composts can be wood based, wool based, or coir based, for example. Commercial brands of all purpose compost often also include other ingredients intended to promote healthy and strong root formation and plant growth.

For example, all purpose compost often includes materials designed to help in aeration, such as vermiculite or perlite. Vermiculite is a light, spongy material made from mica, and holds more water as well as aerating the mix. Perlite is expanded volcanic glass and gives a compost that is more free-draining. Though these can be helpful for gardeners, it is worth noting that neither is a particularly eco-friendly option.

Some all-purpose or multi-purpose compost brands will also incorporate some controlled release synthetic fertilizer capsules that will slowly release nutrients over a matter of weeks or months. If you wish to garden organically then these are, of course, options that should be avoided.

What Are Its Benefits?

A good quality all purpose compost is usually the cheapest sort of compost that you can get. Short of creating your own compost at home, of course, this is the most affordable option.

A good quality all purpose compost also makes things easy for new gardeners, as they do not have to think too deeply about which compost they need for specific uses in their gardens or containers.

How To Use General Purpose Compost

As mentioned above, a general purpose compost can be used for a range of different garden applications. While all purpose composts can ostensibly be used for seed sowing and for plants at all stages of their growth, some general purpose composts are much finer grained than others. And the nutrient composition of different all purpose composts can vary significantly.

In general, a good all purpose compost is great for:

  • Topping new raised beds or growing areas (for example, those made with the no dig lasagna method) in your garden.
  • Mulching existing beds, borders or growing areas to replenish fertility and protect and improve the soil.
  • Filling containers for a range of indoors and outdoors grown plants. (Any that do not have more specific needs when it comes to their growing medium.)

What Plants Is All-Purpose Compost Good For?

An all purpose compost is good for placing as a mulch, or using as a growing medium for mature plants (some are also fine for seed sowing, seedlings and cuttings, though this depends on the particular brand and its formulation).

It can be very useful in growing a wide range of plants including many fruits and vegetables in a food producing garden, shrubs, trees, bedding plants and herbaceous perennials.

When To Avoid Using It

Avoid using an all-purpose compost for plants that have more specific requirements when it comes to their growing medium. For example, some plants are ericaceous and require an acidic compost growing medium or mulch. Others require better drainage than a typical all purpose compost provides.

We recommend that you avoid purchasing all purpose composts that contain peat, due to the environmental concerns. We also suggest that you look into making your own, so you can significantly reduce the amount of multi-purpose compost you must buy in future.

Frequently Asked Questions

Can You Use All Purpose Compost For Acidic Loving Plants?

Whether you bought it or made it yourself, the pH level of an all purpose compost can vary quite a lot. Usually, it is neutral to mildly acidic. It will have been formulated to be suitable for as wide a range of plants as possible. However, because it has been formulated to suit many plants, it will not be suitable for some – including plants that like acidic growing conditions.

For plants that require acidic conditions like, for example, azalias, many heathers, rhododendron, blueberries, etc.. you should use an ericaceous compost. This is an acidic compost that has been formulated to provide growing conditions with a lower (more acidic) pH. Ericaceous compost that you either buy or make yourself will be a better choice for growing these plants in containers, or for using as mulch around them.

How Long Does All-Purpose Compost Last?

How long all purpose compost will last before it is used depends to a large degree on how it is stored. If it is kept dry, and in a sealed container, then it should last indefinitely.

On the other hand, if the container is breached, or the compost is on the soil or open to rainfall, the nutrients within it will slowly start to leach out and the materials will continue to break down. The compost will usually have depleted to the point where it is no longer ideal for plant growth within a few months.

If you have used an all-purpose compost in containers, you should note that you’ll need to replenish the nutrients in it over the growing season to encourage plants to continue to grow strong. To give plants a boost, you can top dress or mulch around the tops of the containers with organic matter/ soil enriching materials. And you can use organic liquid plant feeds to give plants nutrients more quickly. With many plants, you should plan to replace the growing medium in the pots every 2-3 years.

If you are mulching around plants in your garden, compost is great as a slow release fertilizer and will also improve the soil. Micro-organisms will feed off organic matter in the compost that has not yet fully decomposed, and soil biota will help incorporate the compost and its nutrients into the soil below. You should plan on replenishing the growing areas with compost or other fertilisers/ soil amendments at least once a year.

Should You Use This Compost Type For Indoor Plants?

All purpose compost is fine for many houseplants. But certain groups of plants, like orchids, bromeliads, succulents and cacti will require more specific compost mixes and will not thrive in an all-purpose compost.

Can I Use All-Purpose Compost For Seeds?

Some general purpose composts will be fine for seed sowing, seedlings and cuttings. Others, however, may not be the best choice for these stages of plant growth. What it comes down to is the texture of the compost, and how fine-grained it is. If it is relatively fine grained, it will often be suitable for seed starting.

Remember, seeds need water, oxygen and the right temperatures for germination. But they do not yet need to take in nutrients from the soil. This means that special seed composts are sometimes used, which tend to be low in added nutrients, yet have a texture that helps seeds and young seedlings.

One benefit of using a more general compost (either an all purpose compost you have bought which has a fine enough texture, or a compost/ potting mix you have made yourself at home) is that the seeds can be left to grow on in this medium. So don’t necessarily have to be moved to different containers filled with a different growing medium for the next stage of their growth.

Do Mice Eat All-Purpose Compost?

Mice will not eat a potting mix or compost itself, unless it is a poor mix with non-decomposed organic material. However, they may enjoy the friable texture of the mix and use it to hide within, and as a place to store bits of found food.

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