Top Tips for Trouble-Free Tomatoes

, written by Benedict Vanheems gb flag


If you could grow just one crop, what would it be? For me it would be tomatoes because only by growing your own can you get the very best-tasting varieties and have the privilege of picking the fruits at their most delicious.

To ensure a trouble-free crop, we need to show our tomatoes a little love and put them in the strongest position possible for a bountiful harvest. Let me show you how!

Supporting Tomatoes

Making sure your tomatoes are correctly supported is one of the most important things you can do to prevent disease and rotting fruit. The best time to get the supports in position is at planting time.

The type of support tomatoes need depends on the kind of tomato you’re growing:

A stout cane or stake is needed to keep tomatoes up off the ground

Vining (Indeterminate) Tomatoes

Left to their own devices, vining (or indeterminate) tomatoes would sprawl along the ground, but it’s better grow them vertically to make the most of space, improve air circulation, and minimize the transmission of soil-borne diseases such as septoria leaf spot.

Tie plants to sturdy canes or stakes. You can also use string supports for greenhouse-grown tomatoes. Suspend stout string from your greenhouse’s roof, and tie or loop the other end around the rootball of the plant when planting. Weave the stem around the string as it grows. Weaving stems into position is best done in the afternoon or early evening, when stems are more supple after warming up during the course of the day.

Another option is to use cattle panels or square mesh stock fencing. Cut it to form a tube then secure the ends together, and pop in place over your tomato – a simple but very effective tomato cage.

Tomato cages help support the heavy fruit trusses

Bush (Determinate) Tomatoes

Bush (or determinate) tomatoes don’t need nearly as much attention as vining varieties. They are much shorter and stockier than vining tomatoes, but even these types will benefit from some sort of support, particularly as the plants get laden with heavy fruits – canes, stakes, or tomato cages all work well.

Pruning Tomatoes - Foliage, Tips and Sideshoots

It’s tempting to let tomato plants just grow as big as possible – after all, more plant means more tomatoes, right? But it can actually cause problems if you let tomato plants grow unchecked.

Ideally, we don’t want any leaves to come into contact with the soil, so prune out leaves to keep them well clear of the soil surface. Once plants are more established you can remove all the leaves up to the first flower or fruit truss. Doing this also helps with airflow, reducing stagnant air which is a prime breeding ground for air-borne diseases such as blight.

Remove unproductive sideshoots to improve fruiting and maximize airflow

Vining tomatoes will need any sideshoots removing. Also known as ‘suckers’, they will appear where the branches join the main stem and it’s important to pinch or snip them off in order to concentrate more of the plant’s energy on fruit production and to avoid issues with overcrowding and reduced airflow. So long suckers!

Pruning leaves and sideshoots is best done in the morning as plants are more swollen after the cool of the night. This way they should snap off neatly, giving a clean break.

In areas with shorter growing seasons it’s a good idea to ‘stop’, or pinch out, the leading shoot of vining tomatoes, because this redirects the plant’s energies into producing fruits sooner, reducing the amount of unripened tomatoes left at the end of the growing season. Stop plants once four fruit trusses have formed on outdoor tomatoes, and once the main stem reaches the greenhouse roof for tomatoes grown inside.

Keeping the soil covered with organic matter preserves soil moisture and helps to top up fertility

Cover the Soil

Where do tomatoes get the nutrients they need to grow well and fight off disease? The soil, of course! Consistent nutrients and moisture at the roots is essential to a healthy crop. Before planting your tomatoes, add an inch (3cm) layer of compost, and then you shouldn’t need to add any more compost over the course of the growing season. However, adding a layer of mulch such as shredded bark or grass clippings will always be welcome.

Mulches have lots of benefits, including reducing weeds, shading soil to keep roots cooler in hot climates, moisture retention for more efficient use of water, and as a barrier between the soil and the foliage on your tomatoes, again reducing the disease risk. When you water there is less chance of soil splashing back onto the plants and, since mulches reduce soil evaporation, you won’t have to water as often.

Mulches will promote more even soil moisture, helping avoid issues such as fruits splitting, and blossom end rot, when calcium fails to reach the fruits due to a lack of water flowing through the plant.

Wet foliage is more prone to disease, so target your watering carefully

Watering and Feeding Tomatoes

So how often should you be watering? The answer is: it depends!

In my temperate climate I might water tomatoes in containers once a day during a warm, dry spell, dropping to maybe twice a week in cooler, cloudier weather. If you’re growing in a hot climate then you’ll probably find you need to water more often than this. Tomatoes grown in beds and borders will usually need watering less often than those grown in containers.

It’s important to avoid over-watering, especially after a dry spell, as this can cause the fruits to suddenly swell and the skins to split open under the resulting pressure. Overwatered tomatoes are also less tasty.

If in doubt about whether to water, do the finger test. Stick a finger down where the roots are – perhaps an inch or so beneath the soil surface, beneath any mulch - and assess how damp it is down there. If it’s dry, water. If it’s damp, don’t. Over time you’ll get a sense for how moist it’s likely to be.

When you water, avoid wetting the leaves to reduce the chances for diseases to get a foothold. Try not to splash back soil or potting mix onto the leaves.

Tomatoes in containers need careful management to keep them evenly moist and well fed

Tomatoes are hungry plants. Tomatoes grown in soil improved with plenty of compost may not need additional feeding, but plants in containers, growbags and straw bales certainly will. Use a liquid tomato fertilizer for this because it will have a good balance of nutrients specifically suited to tomatoes and other fruiting vegetables. Water it on at the rates and frequency recommended on the packet.

Never let container plants dry out. Potting mix is a pain to rewet after it’s dried out, so try to prevent this from happening in the first place. An irrigation system can help, as will growing in larger containers, which are slower to dry out. And remember you can also mulch the surface of potting mix in the same way as the soil. If your potting mix does dry out, rewet it by sitting it in a reservoir of water to slowly and completely rehydrate.

Comfrey can be processed into a nutritious tomato feed

Plants can also be fed with a homemade comfrey feed. Avoid growing wild comfrey in your garden, as it can become very invasive. ‘Bocking 14’ is a well-behaved, garden-friendly variety.

To make a comfrey feed, stuff comfrey leaves into a bucket and weigh them down with a brick. Collect the liquid that oozes out as the leaves break down. Drain off and store the comfrey liquid. Top up the bucket with fresh leaves as they break down. The comfrey should be dissolved around one part comfrey liquid to ten parts water.

Blight is a devastating disease of tomatoes which is hard to avoid

Reduce the Risk of Tomato Blight

Late blight is the most widespread threat to our tomatoes. It’s notorious for cutting down plants in their prime, dashing hopes of summer-long harvests. This disease is carried on the wind, so it’s very difficult to avoid, but there are precautions you can take. Make sure to water carefully – taking care not to wet the leaves – and water in the morning if you can, so the soil surface has a chance to dry off during the course of the day.

As I mentioned earlier, cut off the lowest leaves so there is no foliage in contact with the soil, and soil can’t splash up onto the leaves when you water.

Keep greenhouses well-ventilated to reduce the risk of disease

Encourage that all-important airflow. Pruning off those lower leaves and sideshoots will help, but make sure plants are properly spaced too. If you’re growing in a greenhouse or tunnel, open up the doors, vents and windows as wide as they go to encourage good ventilation. Tomatoes grown under cover will be less susceptible to blight, but they are no means immune, so watch out! Inspect plants regularly and remove infected material the very moment you spot it – act fast as blight spreads quickly.

If possible, avoid growing tomatoes near potatoes because blight can pass between them, affecting both crops. Remove all traces of tomato and potato crops, including tubers, at the end of the growing season.

If blight is a consistent problem in your area then growing tomatoes under protection such as a greenhouse or tunnel is often the best solution.

Tomatoes can also suffer from early blight, which isn’t usually as serious, but it’s important to remove infected leaves when you see them.

Hornworms can be tricky to spot!

Tomato Hornworms

The tomato hornworm is one of the most common tomato pests for North American gardeners. Hornworms weaken plants by eating the foliage. Being green in color, they don’t exactly stand out against the leaves, but a little tip is to head out at night and shine a blacklight or UV light on your plants. Incredibly the hornworms glow in the light, making them easy to spot and pick off.

Taken together, these simple steps should power your tomatoes through the growing season, giving you truly trouble-free plants and a delicious harvest!

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Show Comments


"My tomato bushes are 1.6 meters tall, are they too tall"
Ken on Tuesday 3 January 2023
"This year I have lost my complete crop of San Marzano tomatoes due to blossom end rot. All were grown in grow bags each bag was in a self watering wick fed tray, so never drying out. However this year I had changed to a 100% peat free compost medium. I wonder if these peat free mediums do not evenly soak through. I have also grown many cherry type tomatoes, these seem to be growing successfully without any diseases or fruit splitting - a sign of uneven watering. All grown under glass What success have others had with different peat free mediums?"
John Clarke on Sunday 3 September 2023
"Thanks for sharing your experiences John. I think you are right that peat-free composts do require more consistent watering to avoid problems, but a good peat-free compost should be just as good a peat-containing one. I would also check how much/often you are feeding your tomatoes to make sure they are getting a good, regular supplier of what they need, using an organic tomato feed of course. Will be interesting to read others' experiences."
Ben Vanheems on Tuesday 5 September 2023

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