Planting and Growing Tomatoes in Grow Bags

In the UK there are some varieties of tomato plants that do well outside, however, lots of tomato plants are better suited to being in a greenhouse. You can, however, grow tomatoes successfully, inside and outside by planting them in grow bags. Grow bags are perfect for all different varieties of tomato and are great when you want to grow tomatoes on a patio or balcony too.

I often daydream about having one of those huge polytunnels that you see at garden nurseries and growing rows and rows tomatoes inside. Maybe one day, who knows. But for now, we are sticking to the smaller space version for growing our tomatoes using grow bags to plant them.

Pre-filled Grow bags or growing bags as they are sometimes called, are a long, shallow, rectangular shaped bag filled with compost and fertiliser. You can also purchase plastic of fibrous ones that are empty, they act like pots and can be filled with your own variety of compost to suit your needs.

Tomatoes are a delicate plant, and aren’t as forgiving as other fruit and vegetables such as beetroot or potatoes. But, with the right conditions, you can be harvesting your own tomatoes to make many different recipes, such as this Autumn chutney or the creamy tomato sauce for these mozzarella frittas. Ensure you provide them with the right conditions and you will be fine.

I just love the smell of a tomato plant. To me, greenhouses always feel like they are missing something without a tomato plant growing inside.

There are many varieties of tomato plants which you can buy or grow from seed. All are suited to varying conditions. You can get outdoor varieties, which are a little more hardy to British weather. Bush tomatoes, often do well on patios and in pots. Tumbling cherry tomatoes, are suited to handing baskets. Indoor greenhouse tomatoes, are more delicate than other types, but offer up the most choice for variety.

What You Need to Plant Tomatoes in Growing Bags

tomato plants, grow bag and supportive canes
  • A Grow bag
  • A Grow Bag tray (optional)
  • 2-3 Tomato Plants (depending on the size of your grow bag)
  • A supportive cane for each plant
  • Tomato plant feed
  • Garden Twine
  • A Sharp Knife or Scissors
  • A small Trowel

How to Plant Tomatoes

Whether you have purchased the tomato plants or grown them from seed, it is ideal to wait for them to produce their first flowers before transferring them to a growing bag.

Before you start planting your tomatoes, it is a good idea to give them a good soak in water for an hour. This prepares the young plants for the shock of being transferred and helps support them through the transition.

When you have purchased your grow bags, you may find that the contents are rather compact, so before cutting the bag open, move it around and give it a shake to loosen up the soil inside. This will make it easier to plant up and will also help the roots of the tomato plants find their way easily.

Make a few small holes in the base of the bag for drainage and place it in a tray (if you choose to use one) in the destination place. It won’t be as easy to maneuver the bag once it is planted up.

tomato plants being planted in a grow bag

Using a sharp knife or scissors, cut holes in the top of the bag to expose the soil inside ready for planting. You will usually find that commercial grow bags will show you some pre-made markings to give you an idea of where to make your holes.

Remove enough compost to make room for the plants and carefully remove the plants from their pots. Place the plant gently into the hole. The root ball should sit just below the top of the bag. Cover it with some of the dug out compost and compress the compost slightly, using your hands, around the base of the plant.

Insert the bamboo canes or support system next to each plant and loosely tie the tomato stem to the cane using some garden twine. Ideally, make the twine into a figure of 8 when you tie it as it creates less pressure on the stem as it grows.

close up example of the figure of 8 twine

Feeding and Watering Tomato Plants

When it comes to watering your grow bag, be sure to do it regularly to stop it from drying out. If you water inconsistently, you will find that as the fruits begin to grow, they will have splits on the skins. If you are worried about forgetting to water or not doing it right, an option is to buy a product that does it for you.

You can purchase a self-watering grow bag tray, which you add water to. The tray has spikes which pierce the bottom of the bag and deliver water directly to the roots at an optimal rate. If you choose to water the plants yourself, don’t drown them, but instead, provide them a steady supply every day when it is particularly hot, or every other day, if it is cooler.

Remember, grow bags will dry out more quickly than when you plant in the ground, so it’s important to check your plants daily and decide what they need.

Tomato plants like a high potash feed in order to grow the best fruit. You should feed your plants weekly once the tomato flowers have begun to grow. Many garden centre will sell an appropriate tomato feed, that has everything your plants need to thrive.

Caring for Tomato Plants

As well as feeding your plants weekly, keep tying the plant to the cane using the figure of 8 pattern, as it grows up to make sure it’s well supported.

If you are growing a cordon variety of tomato plant, which is usually the case if you aren’t growing bush or cherry tomatoes. You will need to create a main stem with 7 flowering beams.  To do this, remove any little side shoots that you find growing in the joint between the stem and the flowering beams.

Once you have grown 7 flowering beams, pinch away the leaves at the top of the plant, leaving a height of 2 leaves above the last beam to prevent further growth. Cordon varieties are a little more work than their bushier counterparts.

Bush varieties do not need to be pinched out, so are much less maintenance than the cordon variety. If you are a beginner and would prefer to start with something easier, bush tomatoes are the way to go.

If you don’t have a greenhouse, fear not. There are plenty of outdoor varieties, small patio varieties and even cherry tomatoes that you can grow in hanging baskets and will produce an abundance of tiny little fruits if you look after them properly. Tomatoes like a sunny, sheltered area so be sure to place them away from areas which are exposed to the elements.


What month should I plant tomatoes?

You start your seeds indoors in Spring. The tomato plants should be planted out after the risk of frost has passed in the summer. Warmth is most important for tomato plants, to allow the tomatoes to ripen.

Do tomatoes need full sun?

Tomatoes thrive in full sun, but you can still get a decent crop of partial sunlight, providing they receive at least 6 hours of sun a day.

Can I plant tomatoes if I don’t have much space?

Tomatoes are great plants for balconies, hanging baskets or even window boxes. There are varieties you can buy that are perfect for pots, patios and small spaces.

What plant feed should I use for growing tomatoes?

A plant food with high potash content is ideal. You can buy specific tomato plant feeds from most garden centres. Feed plants weekly as they grow.

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