Best peat-free composts for pots of summer bedding in 2023

A pot full to the brim with bright, cheerful flowers is a great way to cheer up any patio. Or you may prefer to harvest from veg from your containers – dwarf tomato plants and peppers can look just as attractive. 

But for great plants you need a great compost. Which? Gardening has been testing compost for almost 40 years,, so we know how variable they can be and the difference a Best Buy can make. 

We tested 25 peat-free composts that are meant to be used in pots. Peat-free compost is the most sustainable option, so you can do your bit to reduce the release of CO2 by making the switch. 

Peat composts will be banned in the UK by the end of 2024, and in our past trials we've found there's little to be gained from peat when growing in containers. Large pots hold a lot of compost, so filling them with peat is particularly wasteful. 

Find out which composts are Best Buys for patio pots this year.  

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Best Buy composts for containers

We tested 25 peat-free composts from a wide range of manufacturers and retailers. From these we found five Best Buys that will grow pots full of flowers and veg. 

Several of our Best Buys also scored very well in our trial of composts for young plants –  that's seedlings and plug plants. This means that by choosing carefully you can buy a compost that can be used to pot up your plug plants and then plant them out into large containers. It will, in short, help to nurture your plants from when you first get them at the garden centre to the first frosts. 

Peat-free composts are made from a wide variety of different materials and so aren't as uniform as peat composts. The composts in our trials are made from wood fibre, composted bark, coir, wool, bracken, green compost created from green bin collections, and anaerobic digestate (the left-over material from green energy production). 

Some gardeners struggle to adapt to using composts that are fundamentally different to peat, particularly when there are so many mixes on sale. Which? Gardening only uses peat-free compost in its growing trials, so we know the stumbling blocks. Look at our expert guide to peat-free compost for everything you need to know about what's in your compost and how to get the best results from it. 

Getting started with summer pots

Now is the time to start thinking about what you want to grow in your pots this year. If you want to grow from seed, you can start your bedding plants from now onwards, including sweet peas, marigolds, dwarf sunflowers and smaller cosmos varieties. There are also some great veg plants that do well in containers, such as tomatoes, peppers, cucumbers, potatoes and chillies. Alternatively, you can get hold of some dahlia tubers and pot them up ready to go outside after the last frost. Our guides to grow your own and the best plants are a great place to start choosing. 

You might already see plants for sale in the garden centre, but unless you have a greenhouse or a lot of window sills, it's worth delaying your shopping for a few weeks. There is a huge choice of plants you can grow and a vast number of varieties. Garden centres have a good choice, but if you want to pick from a wider selection, it's worth taking a look at online retailers. 

Which? Gardening asked its members to review and rate the best seed and plant suppliers, so you can buy with confidence. 

You needn't limit yourself to greenhouse-raised annuals, either, as there are some great perennials that look good in pots, such as lavenders, half-hardy salvias and heucheras.

Looking after your plants

Plant up your pots outside from mid-May onwards, depending on where you live. Some parts of the country are prone to late frosts that might kill your tender plants. 

Feeding your plants is crucial if you want plenty of flowers and a good harvest of veg. While most composts contain enough feed to last four to six weeks, you need to supplement this. The easiest was to do this is with a controlled-release fertiliser. These granules slowly dissolve, releasing nutrients as the weather gets warmer and when the soil is moist and are a great way to feed your plants for months on end. Choose a Best Buy controlled-release feed and mix it into your compost when you pot up your plants. 

Towards the end of the summer you may notice your plants starting to run out of steam. This is probably because the controlled-release feed has run out. At this point you need to liquid feed your plants, around once a week using a Best Buy liquid feed. This should ensure your plants continue flowering right up until the first frosts arrive in November. 

Of course, regular watering is a must, but you might also want to think about being water-wise. Some councils and water companies offer discounts on water butts, and a good watering can helps you to be aware of exactly how much water you're putting on your plants. An automatic watering system can save time and it can also be water efficient if you're careful to set it to water just as much as your plants need and no more. 

Finally, remember to deadhead your plants for the best results. Some, such as the modern varieties of petunias, will keep flowering without this, but others give a better show if you remove spent flowers. Our recent trials have shown that cosmos, marigolds and bidens all benefit from regular deadheading.