Tomatoes are so easy to grow that even a novice gardener can be successful! Growing tomatoes in a planter box will increase your chances of success, as this provides them with enough warmth and nutrition to last a whole growing season.
Whether you’re growing your tomatoes in pots on a window-sill, in a grow bag, a greenhouse, or alongside herbs on a sunny balcony, the basic principles will be the same. Tomato seeds are available for every taste, colour, and size you can imagine.
So what’s the best way to achieve a huge crop in a tomato planter box and how can you build one? Read on!
What conditions give a good crop of tomatoes?
- Good seeds. Buy your tomato seeds from a recognised supplier and try to buy organic seeds if you can. Sow them in pots indoors in spring and transfer them into your planter box as soon as the weather improves and there is no danger of frost.
- Good soil. Tomatoes are super-hungry plants and love rich, deep soil where they can spread their roots and grow side branches. Add homemade compost, manure if you can get some, and extras like wood ash, comfrey leaves and well-rotted leaf mould, to provide a balanced soil to feed the tomato plants.
- Sunlight. This is an absolute must for tomatoes so make sure your planter box is in a location where it has direct sunlight for as much of the day as possible.
- Water. Tomatoes get very thirsty so water them as part of your daily routine or even better, set up a watering system so that even if you forget, your plants still get a drink.
- Support. If you’ve never heard of “tying in” plants, you have now! This means tying the stem of a branch onto a support like bamboo stakes or a trellis so that the tomato can climb as high as it likes. This way you can also provide support for a bunch of tomatoes, as sometimes the weight tends to make the whole branch drop.
What size planter box will suit tomatoes?
You know by now that tomato plants need rich, deep soil so your planter box must be at least 1 foot deep and preferably deeper. Think of the size of a grow bag and this is for 3 plants. So if you have only 3 tomato plants, then a planter that will fit 3 plants would need to be at least 3 feet wide and 1 foot deep.
If you empty a grow bag into this planter box size, you may need to top up with compost and garden soil and other additions like sand, some manure or ash, and a handful of comfrey leaves.
See also: How To Fill A Wooden Planter Box
What material suits a planter box for tomatoes?
The nice thing about tomato plants is that they aren’t too fussy. I’ve grown tomatoes in plastic pots, ceramic planters, wooden planter boxes and grow bags, in any space I can find in a greenhouse beside cucumbers and herbs.
So if you are really new to this, choose any planter that suits your budget and try it out. Try growing different varieties of tomatoes to find out which ones you like best. You will never go back to the dull taste of shop-bought tomatoes again!
Some gardeners swear by the taste of Gardener’s Delight and others like huge plum tomatoes, which originated in Italy or Spain. In my experience, the smaller tomatoes are generally sweeter but if you’re planning on using them for pizza sauce, then the large ones do very well.
Tomatoes can be grown which are resistant to tomato blight and this is very useful in the UK summer weather. See more on diseases and pests below.
Do I need to waterproof a tomato planter box?
Yes, it’s essential to have good drainage but you’ll also want to stop water leaking from your planter box after watering. It’s also important that the planter box material doesn’t rot if it’s made from wood.
See some ideas for how to make your planter box waterproof here.
DIY tomato planter box
Tomatoes aren’t particularly fussy plants and it’s easy to build a tomato planter box that they will thrive in.
Make a planter box from a cardboard box
- Drainage. Make a hole to fit a water adapter which you can buy in any hardware shop. You will need a male and female part, which fit together.
- Tape the end of the box with masking tape, sellotape or stronger duct tape.
- Line the box. Use a plastic bag (or 2 for strength) to line the box, and staple these in place.
- Fill the box with soil and get planting!
Make a planter box from pallets
You can make a fantastic pallet box planter for your tomato plant.
Make a planter box from used plastic containers
We all have old containers lying around that used to hold various paints, chicken pellets, pet food and so on. Make a hole in the base of an old pot using a drill and then line it in the same way as the cardboard box above.
Now your tomato planter box is constructed, waterproof, and full of soil, all you need to do is choose your seeds.
What kinds of tomatoes can I grow in the UK?
There are many excellent seed suppliers in the UK like Fothergills and Thompson and Morgan, and gardening centres offer a wide range of seeds from which to choose. Some tomatoes grow well outside but certain varieties of tomatoes prefer the warmth of a greenhouse so check the packet before you buy.
- Gardener’s Delight – a classic favourite with small tasty fruits.
- Marmande – larger tomatoes that can be pureed, frozen, etc.
- Marbella – large tomatoes, and these plants are heavy fruiters.
- Plum – Italian-style tomatoes with an elongated shape.
- Garden Pearl – rich, red colour, small with several to a vine.
- Sungold – unusual orange-yellow coloured tomatoes when ripe.
What should I plant with my tomatoes in a planter box?
Tomatoes are very hungry plants but they do grow well with herbs so put some basil, chives, coriander with your tomato and you have a ready-made Italian salad to pick.
Diseases and pests that affect tomatoes
This is every tomato grower’s nightmare and it spreads like wildfire so remember to use sterilised soil if you can to avoid this. It can spread from potatoes so try not to grow these plants together.
It happens in wet conditions so if it is a really dry summer you probably won’t encounter it. The leaves turn brown and die and when you look at the roots, they are brown instead of creamy white. The tomatoes will have green spots and look diseased.
How to fix it: Get your gloves on and bag up the whole plant without spreading the fungus to plants close by. Wash your hands thoroughly after touching any diseased plants.
Pests include mainly slugs and snails, which eat the young plants. Remove them to a new location!
Red spider mites
Red spider mites attack the leaves of tomatoes in a warm dry area like a greenhouse.
How to fix it: Make a solution of washing up liquid and water and spray the plants. Rinse with fresh water and then wait to see if the little red pests have moved on. They hate damp conditions so keep that spray handy for future use.
Caterpillars may munch the leaves and snails may try to eat developing fruit so keep your eyes open and move them to a different part of the garden or compost heap if you have one.
Tomato box planter plans
You’ll need basic carpentry skills for these designs: