​Buying quantities of bagged

Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own.

Here's what you’ll need to make your own compost mix: 

Tools 

• A shovel 

• A garden sieve (or metal colander)  

• Gloves 

• An old compost bag to store leftover mixture 

Ingredients 

• Garden soil – adds stability to your mix and its particles hold on to water and

  To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key plant nutrients usually derived from soil are nitrogen, phosphorus and potassium, while carbon, oxygen and hydrogen are absorbed from the air. Other vital soil nutrients include magnesium, calcium and sulphur. Gardeners can add nutrients by applying fertilisers (either artificial or naturally derived) to boost plant growth and improve flowering and fruiting.

  nutrients

• Organic matter, like homemade garden compost, leafmould or well-rotted manure – adds nutrients as its broken down and creates air spaces so roots can breathe

• ​Sharp sand or grit – to improve drainage

1. Collect and prepare some garden soil to use as a base for your compost mix 

   Taking spadefuls from around your garden prevents you lowering the soil level in just one area. Remove any weeds from the soil, sieve it to remove stones and debris and set aside.

2. Gather some organic matter to enrich your mix

   Materials like homemade garden compost, leafmould or well-rotted manure can be made at home or locally sourced. Sieve to remove any large clumps and set aside.

3. Mix the ingredients 

   A mixture of 70% garden soil and 30% organic matter creates a good general potting mix for planting up trees, shrubs, perennials and fruit. If your garden soil is heavy, reduce the soil content by around 10% and add some sharp sand, grit, or bulky organic matter in its place to improve drainage.

4. Fill your containers for planting

   Store any leftover mixture in an old compost bag, labelling it so you know what’s inside. Keep this somewhere cool and dry until you next need to use it.

Garden soil is the main ingredient of homemade compost, but it varies considerably from garden to garden, with different proportions of clay, sand and loam and therefore different water and nutrient-holding abilities.

It’s important to bear in mind the type of soil you have when using it as a base for compost mixes, adjusting the ratio of ingredients accordingly: 

• Clay soils are fertile but often slow-draining, so mixes based on clay soil will need more sand, grit or bulky organic matter adding for drainage 

• Sandy soils tend to drain well but don’t hold on to nutrients, so mixes based on sandy soil need a higher proportion of rich organic matter like well-rotted manure.

The different soil types found at RHS Garden Wisley

The plants you are intending to grow will also determine what the compost mix consists of. Trees and shrubs in pots, being long-term plantings, need a good amount of garden soil in their mixes, while short-term bedding plants need a higher proportion of organic matter to provide the nutrients for a dazzling display.

Tweaking your mix, by adding a bit more of some ingredients and a bit less of others, will help you find one that works for you.