These Are The Benefits Of Loam-Based Compost (And How You Can Make Your Own)
Elizabeth is a Permaculture Garden Designer, Sustainability Consultant and Professional Writer, working as an advocate for positive change. She graduated from the University of St. Andrews with an MA in English and Philosophy and obtained a Diploma in Applied Permaculture Design from the Permaculture Association.
Reviewed By DAN ORI
Dan has over 27 years’ under his belt caring for plants and gardens. Working as a Horticultural Instructor and Consultant, he draws on a diverse range of experience that includes working as a Head Gardener, Tree Surgeon, Garden Centre Trouble Shooter, and writer of academic papers. Dan has a Level 3 Diploma in Horticulture and is currently a candidate for the RHS’s most prestigious award – The Master of Horticulture.
IN THIS GUIDE
John Innes composts are popular here in the UK, and in other countries.
What Is Loam-Based Compost?
A loam-based compost is a compost that contains a certain proportion of loam soil.
Most potting composts do not contain any soil at all. But there are some – most notably the John Innes composts, that do have some ‘soil’ in their composition.
It is worth noting that the common John Innes loam-based composts contain soil ingredients that are not necessarily loam in their modern formulations.
Loam is the name given to soils that are balanced mixtures of mineral components of different sizes: clay, sand and silt. They also have an organic matter component.
These soils are the best soils for gardeners. They combine the best qualities of different soil types and are great for plant growth.
The loam in loam-based composts is sterilised to get rid of weeds, pests and diseases.
This means that the gardener should encounter fewer problems than they would with a non-sterilized soil-based growing medium.
There are several different common John Innes composts, or potting media that are on the market today. These are:
- John Innes Seed Compost – for seeds and cuttings
- John Innes Potting Composts (Soil Mix and Fertiliser Base) – best for established plants and general use
- John Innes Compost No. 1 – for seedlings and cuttings
- John Innes Compost No. 2 – for transplanting young plants or plants that don’t thrive in rich soil like thyme
- John Innes Compost No. 3 – for established plants
- John Innes Ericaceous Compost – for acid-loving plants
There are also peat-based and peat-free composts/ growing media with ‘added John Innes’.
“I strongly suggest trying the peat-free mixes of John Innes,” says Horticulturist Dan Ori, “they perform well and manufacturers are not having to harvest from peat bogs to make them.
“It will take a little adjustment to understand when to water, as it is different to compost containing peat; if you use a moisture meter to help you judge when to water, you will find it an easy transition.”
Read on to learn what exactly goes into each of these different soil-based growing media mixes.
What Is It Made Of?
The various types of loam-based John Innes compost have different ingredients and contain materials in differing quantities.
Here are some details to help you understand what is in John Innes loam-based composts, and how to make these products yourself following their recipes.1John Innes potting compost. (n.d.). Royal Horticultural Society. Retrieved March 20, 2023, from https://www.rhs.org.uk/soil-composts-mulches/john-innes-compost
John Innes Seed Compost is used for sowing seeds, and for cuttings, and seedlings can be grown on in it until they are ready for pricking out. It comprises:
- 2 parts loose bulk medium sterilized loam.
- 1 part peat or peat substitute. (Peat is often replaced with other materials and this is a more eco-friendly choice.)
- 1 part coarse horticultural sand.
John Innes soil mix is:
- 7 parts sterilized loam.
- 3 parts peat or peat substitute.
- 2 parts loose sand.
And John Innes fertiliser mix (also known as John Innes base) is:
- 2 parts by weight of hoof and horn meal.
- 2 parts by weight of superphosphate.
- 1 part by weight of sulphate of potash.
John Innes Compost No.2 is used to grow many houseplants, and vegetable plants in containers. For each 2 gallon bucket of soil mix, add 56g of fertiliser mix, and 10g ground chalk.
John Innes Compost No.3 has even more nutrients. It is used for established trees, shrubs and other mature plants, and mature indoors plants that will remain in their containers for a long time. This mix is also good for particularly ‘hungry’ plants like tomatoes, for example. Add 84g of fertiliser mix and 15g of ground chalk.
What Are Its Benefits?
Loam based composts can be beneficial because the loam helps to avoid fluctuations in water and nutrient content in the growing medium.
Since the soil part of the media is very stable, this can be especially useful in situations where plants are placed for the long term.
How To Make Loam-Based Compost
It is important to note that you can make your own loam-based compost mixes at home. And you do not necessarily have to stick to, or remain close to, the formulations described above.
One option if you have a good quality loam soil in your garden is simply to use some of that. You can also make a good loam by stacking turfs of grass upside down until it breaks down.
As mentioned above, all commercial loam-based composts use sterilised loam.
The sterilisation process is undertaken because soil or loam that has not been sterilised can contain weeds, pests and diseases.
It is not especially easy to sterilise loam at home, but it is possible to do so in your oven.
Personally, I use a mix of 1/3 loam (from the garden), 1/3 homemade compost (with well-rotted manure and bedding from our chickens) and 1/3 leaf mould (from autumn leaves) to make a mix that works well for mulching around vegetables and placing in containers.
I do not bother with sterilisation and while there will be the odd weed here and there, and the odd problem, these are not too much of an issue in my organic garden.
What Plants Is Loam-Based Compost Good For?
A loam-based compost can be good for a wide range of different plants. The right loam-based formulation can be used at all stages of plant growth.
But it is important to remember that there are certain plants that need a different formulation, that is more free draining or which contains a specific mix of nutrients.
Loam based composts are generally excellent for the vegetable garden, and for mature plants that will remain in place for longer periods of time.
They can be used for indoors or outdoors container gardens. And can often be the best choices when plants are not grown in contact with the natural soil.
When To Avoid Using It
Commercial composts of this type, either John Innes composts, or composts with ‘added John Innes’ should have been specially formulated to allow for good drainage, aeration, fertility and optimal plant health and plant growth.
It is always important to note that as with other composts, the quality of these commercial composts can vary considerably. Some are much better than others.
The texture of store-bought compost with loam will vary considerably depending on the exact composition of the loam and where the material came from.
Those who are trying to avoid harmful practices and want to garden as sustainably as possible should aim to avoid choosing products that contain peat, non-sustainably sourced loam, and any non-organic fertilisers or other problematic ingredients.
If possible, in order to make your gardening efforts as sustainable as possible, you should try to take a DIY approach, using materials sourced from your own home and garden, or as locally as possible.
