Two further components are added after the elements have been mixed: ground chalk (5g) and superphosphate (20g). John Innes Soil Mix

A base fertiliser then needs to be mixed in at a rate of 3.25kg/m3. You can buy a commercial standard base fertiliser from a garden centre or you can mix your own using equal weights of superphosphate, hoof and horn (or any other slow release nitrogen-rich fertiliser) and potassium sulphate (sulphate of potash). Base fertiliser can also be substituted with a granular controlled release fertiliser. Again, an organic fertiliser could be substituted here. No. 3 contains the highest nutrient levels, and is used for growing mature plants such as shrubs and trees. [1] The base soil is amended with:

Give your seeds a running start with our pick of the best peat-free, coir and perlite seed composts

For those of us who are crazy about growing tomatoes, it’s rather nice to be able to travel both ways.

I’ve mentioned in previous newsletters that a plant that receives everything it needs, and is growing in a well aerated medium, grows a smaller root system – a root system that is better able to cope with the limited space of a container.Issues with drainage and aeration may arise. So generally, it is best either to buy and rely on existing formulations, or to take an entirely DIY approach, as mentioned above. Does Multi-Purpose Compost Contain Loam? 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. 1 John Innes potting compost. (n.d.). Royal Horticultural Society. Retrieved March 20, 2023, from https://www.rhs.org.uk/soil-composts-mulches/john-innes-compost Recommended especially for vegetable seeds and cuttings, this compost’s solid but malleable structure makes it suitable for potting and modular containers as well as ground planting. With so many different types of compost to choose from, sometimes it can be a little difficult to know which is the right compost to buy for your plants. The best way to think of it is by breaking it down into the life cycle of a plant. Seeds and seedlings Before John Innes formulas were developed in the 1930s, all growing media were mixed locally, often from secret recipes held by growers and based on mixtures of composted material and soil. As a consequence, mixes varied widely between growers. Plus, as the soil was not always sterilised, they often contained lots of weed seeds. To overcome these issues The John Innes Centee in Norwich standardised contents and quality for growing media and produced a number of recipes for growing media that producers could follow.

It is worth noting that the common John Innes loam-based composts contain soil ingredients that are not necessarily loam in their modern formulations. This is exactly what it says, sharp grit which can be used in a variety of ways. Use it mixed with compost to improve drainage for taking cuttings and especially when planting alpines either in the ground or in containers. It can also be used to top dress plants, again especially alpines, to stop the soil splashing up and marking the delicate blooms. When used as a top dressing it also stops the delicate plants from rotting at soil level. As the small stones are quite angular it makes an excellent slug barrier, just put a circle around vulnerable plants or stand containers on a layer of the grit. PEAT– Sphagnum Moss Peat in the John Innes Compost increases the total porosity and improves both the aeration and the water-retaining capacity. Peat decomposes slowly into humus.This type of compost can also be combined with peat-based composts and even with peat-free composts. These are used to improve aeration and drainage in heavy clay soil and add body to light sandy soil to help retain moisture and nutrients. It also boosts the soil fertility by adding nutrients to encourage healthy foliage, flowers and root growth. To make your own loam based compost, and we will tell you how later, you need to know two rules. These rules include the quantities of materials and the ingredients of each John Innes loam based compost. Loam is the most important ingredient as it provides a natural reservoir of plant foods, trace elements and contains some organic matter which releases nitrogen slowly to the plant. The loam in J. Arthur Bower’s John Innes is screened and sterilised to avoid any soil-borne diseases and insects. Barks: Mulches and barks are common compost amendments, and provide a range of benefits. They suppress the growth of weeds, regulate soil temperature and help retain moisture. Their natural decomposition also helps release nutrients, increasing soil fertility.

While not exhaustive in terms of compost ingredients and soil amendments, this list below covers notable additions that appear in the products in our roundup.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. You can certainly re-use them but it’s best to tip out all of the old compost and then give your pots a clean to minimise risk of pests and disease. If you have a really large container then you can re fresh the top few inches of old compost with fresh and remember to keep feeding. Why shouldn't I use my own garden soil to pot up plants?