Best grow bags

Grow bags are popular among gardeners – and with good reason. You don't need a pot, as you can plant directly into the bag, and for tender crops they're a great alternative to planting in a greenhouse border. They're a bargain option, too, as they often cost less than bags of multipurpose compost.

Not every bag is as great as it sounds, though, which is why we test them for you. Our Best Buys are perfect for growing summer veg, such as cucumbers, tomatoes, aubergines, chillies, peppers and melons. The best produced lots of large, healthy summer vegetables, while the worst made inadequate yields with pale leaves.

Check out our guides to growing veg

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Best grow bags

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USING THE TABLE The more stars the better. OVERALL SCORE Ignores price and is based on: yield 50%; quantity 20%; cucumber weight 20%; plant vigour after seven weeks 10%. 

Not found the right product for you? Browse all our compost reviews.

Why you can trust our grow bag reviews 

Before testing, we send four secret shoppers to buy all our grow bags in garden centres, DIY stores or online. They buy two of each, making a total of eight of each brand, to see if there is any variation in the quality of each bag.

We use cucumber plants in this trial because they grow quickly, and those in good bags produce an excellent harvest. We have found tomatoes take a long time to mature, as the plants rely heavily on liquid feed, which hides the true results of the grow bags' performance. 

In late May, when the plants each have five leaves, we plant two into each of our grow bags. We grow them in a greenhouse, where they're trained up wires, and we remove sideshoots below the fruit.

We link each grow bag to an automatic watering system, so all the bags receive the same amount of water, and we feed those that require it with a liquid fertiliser. Some of our bags already contain enough fertiliser to last through our trial. 

We pick the cucumbers twice a week, weighing and counting the harvest from each bag over an eight-week period, noting if any are bendy, bulbous or have rough skins. At the end of the test, we harvest, weigh and grade the remaining cucumbers for size.

To find out more, head to how we test compost. Alternatively, take a look at our Best Buy pop-up plastic greenhouses

How to use grow bags

1. Sow your seeds in pots around March time; keep them inside on a sunny windowsill until they are large enough (around 15cm) to plant in your bag  and the last frost has passed. 
2. Put your grow bag in its final position and gently roll it to fluff up the compost.
3. Make some cuts in the bottom of the bag to allow excess water to drain out.
4. Cut along the marked lines on the top of the grow bag to position your plants. 
5. If you only want to put two plants in each bag, use the two outer positions.

Watering plants in a grow bag

• Water regularly so the bag doesn’t dry out. In hot weather, this may need to be up to three times a day.
• An automatic watering system with a timer will help to avoid dry plants.
• Most summer veg will be in the bags for several weeks, so you’ll need to feed them. Add controlled-release feed before you plant by mixing it into the compost where you have cut holes, or add a liquid feed twice a week once the first fruits have formed. Follow the dosage and frequency advice on the bottle.

For more advice on choosing the best compost for you, head to our compost testing results.