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Best Buy composts for containers

By Adele Dyer

You need a great compost to grow pots of bedding and bumper crops of veg. Which? tests find the best composts for pots and containers.

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The best composts that we recommend here are proven to grow plants that are covered in flowers non-stop throughout the summer and large, healthy vegetables. 

Best compost for containers

Pots and hanging baskets filled with flowers are the perfect way to brighten up your patio. Many types of veg are also happy to be grown in containers, so your patio can be productive as well as beautiful. Our tests over the years have shown us that choosing the right compost is vital as compost varies widely. 

You can't tell a good compost by looking at it, and big name brands are not always a sure bet. We test compost every year to find the best ones available for pots and containers. 

Last summer, we grew 12 pots of Begonia 'Bellconia Rose' and Potato 'Sarpo Mira'. We planted them in May and grew them on outside until early October. The plants were judged by an independent assessor, an expert in growing media, in July, August and October, for health, rate of growth, leaf colour and how well they flowered. 

See how all the composts scored by looking at the full results table and see which were Don't Buy composts for containers. 

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Compost Our verdict Begonias Potatoes Score
Compost non-member logo M **** ***** 86%

Best Buy compost for containers

Peat content: 0%

Price per litre: 14p

This compost is made from composted bark and coir. 

It was a Best Buy compost for containers last year and was a Best Buy compost for raising young plants this year. It also narrowly missed out on being a Best Buy compost for sowing seeds in the same trial. 

In the container-compost trial, the bedding pots were brimming over with bushy, lush growth and weighed down with flowers. The potatoes were the heaviest crop in the test and the tubers were large and free from blemishes.

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Compost non-member logo M **** **** 71%

Recommended compost: greatly improved

Peat content: 0%

This was a Don't Buy compost for sowing seeds and raising young plants in 2015, and didn't impress in last year's container-compost trial. However, it fared much better in the wet summer of 2015, when we carried out these tests. 

It's peat-free and contains 50% wood fibre. This helps with drainage, which is a useful quality when it rains a lot. The rest is made from coir and composted bark. 

The begonias were covered in flowers in August, although they were starting to go over by October. We also had a good crop of potatoes. 

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Compost non-member logo M **** **** 71%

Recommended compost: bargain price

Peat content: 50%

Like many of our recommended composts, this is a 50/50 mix of peat and peat alternatives. 

The bedding plants got off to a slow start, but, in August, they were covered with flowers and still giving a good show of blooms in October, which was later than other composts. 

The potatoes were smaller overall than those grown in other recommended composts, but were healthy and blemish-free. 

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Compost non-member logo M **** **** 71%

Recommended compost: large potatoes

Peat content: 50%

This is a 50/50 mix of peat and peat alternatives - in this case wood fibre, bark and green waste, which is now seen in far fewer composts.

We found this compost a good all-rounder. The bedding plants grew rapidly at the start of the season and flowered fantastically well through August, although they had faded a little by October. The potatoes were healthy and had lovely skins, while almost half the containers had large tubers. 

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Compost non-member logo M **** *** 71%

Recommended compost: brilliant bedding plants

Peat content: 80%

This compost was a Best Buy for both sowing seeds and raising young plants. It has a high peat content, at 80% peat, with added wood fibre, which suits seed, small plants and bedding. However, the compost is quite dear. 

The bedding plants were dazzling. They shot away, and were larger and flowered better than most other composts early in the season. They were also superb in August. The potatoes let it down. They looked lovely, but were small, giving a modest crop overall. 

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Compost non-member logo M **** **** 71%

Recommended compost: long-lasting bedding

Peat content: 50%

This compost is a 50% peat and 50% wood fibre mix, like many of the composts in this test. 

The bedding plants didn't romp away at the start of the season, but by mid-summer, the begonias had filled out and gave a great show of flowers. 

The potato crop had a pleasing appearance, but almost all of the tubers were medium in size, with only a few large ones.

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Compost non-member logo M *** **** 71%

Recommended compost: traditional mix

Peat content: 73%

John Innes mixes contain sterilised soil and grit. In this compost, these are added to a 73% dose of peat and wood fibre. 

In this mix, the bedding plants were slow to get established, but by August they were good-sized plants with plenty of flowers. They came into their own in October, when they were still going strong. 

If you prefer potatoes to bedding, this is the compost for you. The containers were laden with well-shaped tubers with unmarked skins. 

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