The best compost will provide all the nutrients and support needed for seeds and veg to grow and thrive, while the worst will leave you with meagre crops and feeble plants.
But the only way to know if a compost is good or bad is to grow plants in it and compare them – something we’ve been doing for more than 30 years.
You are viewing: Which Is The Best Compost
Many people no longer want to buy peat compost as it’s believed to damage the environment and add considerably to global warming. However, peat composts are still the most widely available type in garden centres and are preferred by many gardeners.
This year, we chose to test only peat-free compost. From late 2024, you will only be able to buy peat-free compost in garden centres and DIY stores when the government introduces a ban on peat composts. We firmly believe you can get great results from peat-free composts and we haven’t used peat in our own trials for many years. We have also included Moorland Gold composts which use peat recovered from lakes and dams after being naturally washed from peat heathland by rainwater.
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Best peat-free compost for sowing seeds
The results are updated in mid-January each year.
Read more : Which Of The Following Represents The Different Information Levels
Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.
Best peat-free compost for raising young plants
The results are updated in mid-January each year.
Read more : Which Of The Following Represents The Different Information Levels
Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.
Best peat-free compost for containers
The results are updated in mid-February each year.
Read more : Which Of The Following Represents The Different Information Levels
Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.
What are the different types of compost?
There are two main types of compost: multipurpose and composts for specific use, such as raising plants from seed or growing plants in patio containers.
Multipurpose and all-purpose composts
- Claimed to be suitable for germinating seeds, small seedlings and plants in patio containers, it’s a good general compost, but our tests show that not all are great for all jobs. Look carefully at our results table to find one that is good for all your garden tasks.
- Multipurpose composts are often cheaper than specific-use composts, but check our Best Buys as some specialist composts can give great results.
Seed, potting and specialist composts
- Formulated to optimise plant growth by providing the right conditions to suit the plant at a particular stage in its life, or for certain types of plants such as orchids, cacti or ericaceous plants.
- They often contain a different mix of ingredients to those found in multipurpose composts. These include small amounts of sand, grit or vermiculite in seed and potting composts, bark in orchid compost and mostly gravel and sand in cacti composts.
- The fertiliser may have been adapted, too. Seeds need very little fertiliser to germinate so like the low nutrient levels of seed composts. Young plants need more to fuel rapid growth, and so a multipurpose compost can be a better choice when you prick out your seedlings.
- Ericaceous compost is used for acid-loving plants such as azaleas, camellias and heathers when you grow them in pots. Many have a high peat content. Remember to use an ericaceous feed to keep your plants healthy.
- You may see composts formulated for veg growing. These are very similar to multipurpose composts, but may have a slightly different balance of nutrients. Some are excellent, some are less good.
- Specific-use composts tend to be more expensive than multipurpose composts, but in some cases it’s worth paying a little more.
Tub and basket composts
- Tub and basket composts are formulated to give the right conditions for pots of summer bedding to grow well.
- Some contain a controlled-release feed and/or water-storing granules.
- Tub and basket composts tend to be more expensive than multipurpose compost, but using a multipurpose compost with a Best Buy controlled-release fertiliser and regular watering will also give good results.
Try our Best Buy controlled-release feeds
How much do I need to pay for a good compost?
Compost can be as little as 99p and as much as £25, it all just depends on the type and how many litres of compost you get in the bag. It’s important to remember that a high price doesn’t guarantee quality, though.
In fact, our testing shows really variable results for both cheap and expensive compost. The only way to really know what you’re getting is to look at our results.
Things to look for when buying compost
It’s hard to know if a compost is good or bad just by looking at the packaging, but there are a few things to look out for:
- Dry, clean bags that aren’t torn or faded – in the garden centre choose bags that look new as the contents contain fresh compost. Bags that are faded or are heavy have been hanging around, getting too hot in the sun or soaking up rain, which will damage the compost in the bag. If possible, buy from a garden centre that keeps its compost in a covered area.
- A medium-crumbly texture – is ideal. Composts that are too fine are prone to water logging, while those that are too coarse tend to need more frequent watering. A crumbly structure will allow excess water to drain through, while holding enough water and air for roots to thrive.
- The right balance of nutrients – a good seed or potting compost should have the right balance of nutrients to grow a range of plants during this stage of their development, whereas a multipurpose compost should be able to support plants at all growth stages. Remember that most composts only have enough fertiliser to last around four weeks, so after this you will need to add liquid feed or one of our Best controlled-release fertilisers.
Getting the best from compost
It’s best to buy only the amount of compost you need, and use it up as soon as possible. Store compost in a shed or garage where it will be cool and dry, or undercover, especially through wet weather. If you can’t use up peat-free compost within three months of buying it, use it as a mulch on your borders.
Read more : Which Is Better 45-70 Or 30-30
When you swap to using peat-free compost, you may notice a few differences from using peat. You will need to water carefully as the top of the compost can often look dry or wet, but the rest of the pot could be wet or dry. Get used to putting your finger into the compost to feel below the top layer. You can also pick up your pots. A light pot will need watering, while a heavy one is probably wet enough. Check your pots regularly as they can dry out quickly.
You may need to feed your plants more frequently if you use peat-free composts. Some don’t contain any fertiliser at all and others have fertiliser that runs out quickly. As soon as the growth of your plants slows down, start to give them a liquid feed, including seedlings and small young plants. For more information, look at our reviews of liquid feeds and tomato feeds.
Find out more about why you should buy peat-free compost.
Is it true that I can catch Legionnaires’ disease from compost?
The bacterium responsible for the potentially fatal Legionnaires’ disease has been found in some composts sold in the UK. The chances of you becoming infected are very low, but it makes sense to take the following precautions when handling compost:
- Use compost in a well-ventilated place; keep the greenhouse or potting shed door open and avoid breathing in dust.
- Wear gloves (and no smoking or snacking!) and wash your hands after use.
Want to go peat-free? Here’s our guide on everything you need to know about Peat-free compost: expert guide.
Why Which? compost reviews are better
We test compost for three different tasks; sowing seeds, raising young plants and for use in containers.
- Sowing seeds – we use 25 different composts to grow tomatoes and petunias from seed.
- Raising young plants – we use 25 different composts to grow tomatoes and marigolds, sown as seed and transplanted when they have two non-seed leaves.
- Containers – we use 25 different composts to grow pelargoniums and potatoes.
All three tests are carried out by an expert at a horticultural institute, and the compost for seeds and young plants test takes place in a temperature and humidity-controlled greenhouse. The composts for containers are tested outside once the nights are frost-free. The results are compiled by an independent assessor who’s an expert in compost and plant health.
Our trials have also found these useful facts:
- Quality isn’t guaranteed – our compost trials reveal which composts are consistently good and which can be variable. Choose a Best Buy to be sure you’re buying a reliable compost.
- Growing bags don’t compare – these used to be filled with peat and were cheap, making them an excellent alternative. However, they are now mostly peat-reduced or peat-free and have fertilisers meant for growing veg.
- Watch out for reformulated compost – manufacturers frequently change the mix of ingredients they use and the fertiliser, and this is speeding up as the ban on using peat comes ever closer. We can’t recommend reformulated brands because there’s no guarantee the new product will perform as well as the one we tested. Always use the images above to make sure the Best Buy compost you are buying is the one we have tested.
- Old compost is often on sale – we send secret shoppers to buy our composts, who tell us if they find old compost on sale. It’s a very common problem. We also know from our testing that old compost doesn’t perform as well as fresh compost. To avoid this, buy bags that look new and aren’t faded or heavy, which suggests they have been sitting around in bright sunshine for too long, or have been rained on regularly.
Find out more in our guide on how we test compost. Alternatively, jump straight to our round-up of the best controlled release fertilisers.
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Category: WHICH
