A good compost will help your plants thrive, but the poor will make your plants difficult to grow. Which? The gardening magazine tests compost every year to make sure your pots are full of life all summer long.

We tested 25 composts by growing geraniums and potatoes as many gardeners across the country do.

Find out which composts are best for containers.

Best composts for containers

Throughout the summer, when we test composts for bins, we evaluate the size and health of our plants, as well as the number of flowers on the geraniums and the number and weight of potatoes. We are looking for large potatoes that are easy to clean for cooking.

Our trials have shown that peat-free composts produce great plants. Therefore, the two highest ratings in our test were awarded as Best Buys. In fact, we don’t think it’s necessary to use peat-based compost for patio pots.

For the reasons why it’s best not to use peat, check out our guide to peat-free compost.

What to grow

We found petunias, fuchsias, pelargoniums, begonias and diascia flowers all summer. Choose trailing varieties for hanging baskets, but for pots, choose a mix of upright plants for the center of your pot and trailing varieties that cascade across the sides.

Vegetables also work well in pots and baskets. In addition to potatoes, you can also grow carrots, lettuce, zucchini and many other vegetables in pots. Salads like tomatoes, peppers, and chili peppers are very happy in containers on a sunny patio.

Check out our advice on growing tomatoes and the best varieties for hanging baskets.

For impressive displays, you need a good sized pot or hanging basket. Which? Gardening has found that ideal hanging baskets are about 14 inches wide and tapered at the top, as this will retain moisture so you don’t have to water as often.

For more help and advice, see our guide to planting a hanging basket.

Take care of your pots

Remember to water regularly. Most pots and baskets need to be watered every day in summer and more on very hot days.

All plants need fertilizer, and most composts only contain enough feed for a few weeks. So you have to add a little more yourself. The easiest way to do this is with a controlled release fertilizer that releases feed over many months when the plants need it. Mix it with the compost when you set up your pots and baskets.

Alternatively, you can use a liquid feed that you apply every week. Mix it in your watering can when adding something to your pots and baskets to drink.

Where can I buy plants?

Litter and young vegetables usually arrive in garden centers from Easter. If you are lucky enough to have a greenhouse you can start buying it early, but keep it under cover until the weather warms up. If you don’t have a greenhouse, postpone buying a few weeks until the chance of frost has passed, as frost can easily kill them.

Can you buy plants online and which ones? Gardening has found wide variations in plant quality and service.

Check out the recommendations of our plug plant suppliers to find reliable companies.