Compost is organic material that can be added to plants to improve their health. Whilst making your own compost is a great option for reducing food waste, pre-bought bags can help anyone get started with composting. Given its popularity for gardening, there are many multipurpose composts available, which unfortunately also means there are lots of cheap products worth avoiding! On top of this, universal composts are usually cheaper compared to those designed for specific use. Their economic value only increases once you realise that you can use them for all your plants; from seeds to grown shrubs. Key Features and Considerations When Buying Multi-Purpose Compost i. Fine Texture

In J Arthur Bower’s Multi-purpose Compost we found the chloride levels were more than twice as high as they should be. Chlorides reduce nitrogen, which is vital for green, leafy growth, and this explained why our plants didn’t flourish. The four bags of the Westland Multipurpose Compost we tested had very low levels of fertiliser producing spindly plants that failed to grow as we’d expected. A little more detail to answer the questions above - The survey appears in the current Jan/Feb 2013 Which? garden magazine. The survey was conducted from spring 2012 to find the best buy composts for growing seeds and young plants. Seeing as compost is made up of decayed organic material, it has a lot of great nutrients in it. The three main nutrients, which are often present in shop-bought fertilisers as well, are nitrogen, phosphorous and potassium.In contrast, Vital Earth’s Chelsea Mix All Purpose Compost had very high nitrogen levels. However this is also bad, leading to lifeless plants as high fertiliser levels cause water to be drawn out of plants’ feeding roots, damaging the roots and the plant. Choosing the right compost can be a finely balanced decision, considering the complex blend of minerals, nutrients and organic matter, judged so that plants perform at their best. To avoid too much soil compaction, choose compost with a mixture of large and small particles in it . Wood fibres are good to look out for, acting as a natural component that will allow for soil aeration. Sometimes manufactures will use a mix of materials, including stones and ceramic, which you may or may not want in your garden.

A lot of gardeners find 50 L bags a lot more manageable, although of course they may not offer such good value for money.

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Multi-purpose composts contain a range of nutrients and minerals to help plants thrive. However, you should note how long the compost will continue to nourish your plant for. Most multi-purpose composts will provide nutritional value for around three months. Finally, whether or not compost contains peat is a matter of interest, and contention, for many gardeners. Given that it’s such a polemic issue, you’ll find that the next section is dedicated to the pros and cons of peat-based compost. Peat vs Peat-Free Compost Of course, the big benefit it being multipurpose means that its probably going to be fine for most plants even if the pH requirement is off a little – some plants may not thrive as much as they could with a specific compost but the multipurpose won’t kill them. Volume

Soil-based composts: heavier soil-based blends are usually mixed to the John Innes formulae in 3 grades from John Innes No1 for seedlings, to John Innes No 3 for mature shrubs. It can be used at any stage of a plant’s development, including seed sowing, and the large bag is sufficient for filling approximately 70 small pots (12 cm diameter), or 14 medium pots (22 cm in diameter). They state that although grow bags are not intended for using to raise seeds they tested them as some people do use them for this purpose as they are so cheap. When peat is dug up, to be used as compost (or for other reasons), the store of carbon is disturbed and released into the atmosphere. This is the first downside of harvesting peat – especially on a commercial scale. It can be used for virtually all types of plant and the slightly coarse texture is perfect for all your potting needs as it promotes healthy root growth and resists compaction.Store your John Innes compost from one season to another as the nutrient content may become unbalanced 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. Most universal composts contain a traditional blend of green compost, lime, peat, and materials like bark or wood bits. Cheaper brands will usually add in lots of bark and wood which can be a problem for delicate seeds i.e. leek and carrots. However, you can always sieve out the large bits for your seed bed. ii. Proper Storage J. Arthur Bower’s John Innes are traditional, superior quality soil-based composts. John Innes composts have been widely used by gardeners for over 60 years and are valued for their consistently good performance. J. Arthur Bower’s John Innes No. 2 compost has a nutrient level ideally matched to the needs of most houseplants and vegetables being re-potted into medium sized containers. Now you have the facts, you can make your own informed decision about compost. How Much Compost to Buy