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16 Mar 2021

Compost for patio pots of flowers and veg

Which? reveals Best Buy composts for colourful containers this summer

A great compost helps your plants to thrive, but poor ones leave your plants struggling to grow. Which? Gardening magazine tests composts every year to make sure your pots will burst with life all summer long.

We tested 25 composts by growing bedding geraniums and potatoes, as many gardeners do up and down the country.

Find out which are the best composts for containers.

Best composts for containers

When we trial composts for containers, we assess the size and health of our plants all summer long, as well as counting the number of flowers on the geraniums and the number and weight of the potatoes. We look for large potatoes that are easy to clean for cooking.

Our trials have shown that peat-free composts grow great plants and so the two highest scoring in our test have been named as Best Buys. In fact, we don't think it's necessary to use peat-based composts at all for patio pots.

For the reasons why it's best not use peat, look at our guide to peat-free compost.

What to grow

We've found petunias, fuchsias, pelargoniums, begonias and diascia flower all summer with very little time spent deadheading. Choose trailing varieties for hanging baskets, but for pots pick a mix of upright plants for the centre of your pot and trailing varieties to cascade over the sides.

Veg also do well in pots and baskets. As well as potatoes, you can grow carrots, lettuce, courgettes and many other veg in pots, and salads like tomatoes, peppers and chillies are very happy in containers on a sunny patio.

Take a look at our advice on how to grow tomatoes and the best varietes for hanging baskets.

You'll need a good size pot, or hanging basket for impressive displays. Which? Gardening has found ideal hanging baskets are around 35cm wide at the top and a conical shape as this retains moisture, so you don't have to water so often.

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

Looking after your pots

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

All plants need fertiliser and most composts only contain enough feed for a few weeks, so you'll need to add some extra yourself. The easiest way to do this is with controlled-release fertiliser, which releases feed over many months, when the plants need it. Mix it into the compost when you plant up your pots and baskets.

Alternatively you can use a liquid feed, which you apply every week. Mix it into your watering can when you're giving your pots and baskets a drink.

Where to buy plants

Bedding and young veg plants usually arrive in garden centres from Easter onwards. If you're lucky enough to have a greenhouse you can start buying them early, but keep them under cover until the weather warms up. If you don't have a greenhouse, delay buying for a few weeks until all chance of frost has passed, as they can easily be killed by frosts.

You can buy plants online and Which? Gardening has found huge differences in the quality of plants and service.

Take a look at our plug plant suppliers recommendations to find reliable companies.