Tomato Growing Masterclass: My Blueprint to Success Every Time!

Everyone deserves homegrown tomatoes, freshly picked from the vine! So I’m going to cover all you need to know to grow fabulous tomatoes, from starting seeds through to harvesting armfuls of those glorious fruits – and everything in between!

How to Sow Tomatoes

And it all starts with sowing of course! The best time to get seeds started is about six to eight weeks before your expected last frost date, so they remain a manageable size right up to planting time. But they can’t cope with cold temperatures, and certainly not frosts, so that means they’ll need to be started off indoors in most areas.

There’s no need to buy a specialist seed-starting mix – I just use a standard all-purpose potting mix, sifted to remove any lumps. Fill a small pot with your potting mix and pat down to get it nice and level. Sow the seeds thinly across the top, then cover them over with a bit more potting mix.

Tomatoes need a temperature of around 70ºF (21ºC) to germinate, so anywhere warm indoors would do just fine. To keep the environment around the seeds cozy and moist you can either pop them under a propagator dome or secure clear plastic over individual pots until the first seedlings push through. If you can provide them with bottom heat – perhaps using a heat mat or even just by popping them on a warm household appliance – this will really speed things up, but a sunny windowsill will do the job.

Pricking Out and Transplanting Tomato Seedlings

Once the seedlings come up it’s important to keep them in a bright, warm spot. I use grow lights early in the year, when natural light levels are still quite weak. If you don’t have grow lights, a sunny windowsill would suffice to begin with, but try to move them to a space with more light as soon as possible to avoid the seedlings leaning to one side. One way to mitigate this is to turn pots daily to help the seedlings grow nice and straight, but it’s best to move plants into a greenhouse or other protected space outside as soon as it’s warm enough.

The next stage is ‘pricking out’ or transferring seedlings into their own individual pots of all-purpose potting mix (no need to screen it this time). I like to get my pots filled and ready before working with the seedlings so the roots aren’t exposed for too long. Tip the seedlings out of the pot carefully onto their sides, then gently pull them apart. Handle the seedling by its leaves, never the delicate stem. Use a pencil, chopstick or similar to make a hole in the potting mix then carefully lower the seedling in, using the stick to coax the roots down if necessary. I like to transfer seedlings while they’re very young because the roots are still small and easier to get into the hole.

Tomatoes can actually produce roots all the way up the length of their stems so it’s worth replanting them a little deeper, up to their first ‘true’ leaves – that’s the adult leaves with their distinctive leaf shape, rather than the first two ‘seedling’ leaves, which are smaller and smoother. This creates a stronger, more vigorous plant because more roots sprout right up the length of the buried stem. It also means that if you do find yourself with tall, lanky seedlings – perhaps because they’ve been leaning towards the light – you can just replant them a bit lower to compensate and get everything back on track. Tomato seedlings are very forgiving like that!

Finish by watering to settle your transplanted seedlings in. Don’t worry if they look a bit bedraggled at first – they’ll quickly perk up. Once the weather warms up and there’s no danger of plants being frosted you can leave tomatoes out in a greenhouse, cold frame, plant house or a warm, sheltered spot, so long as you bring them in on colder nights. I find that tomatoes are pretty resilient and can cope with the occasional cool night, but just don’t push your luck – you definitely don’t want them to freeze!

Potting on Tomato Seedlings

If conditions are not yet right to plant your tomatoes but the roots have filled the pot, you can just keep potting them on into a larger container until it’s safe to transplant them into their final positions. It’s very simple to do – just remove the pot from your tomato and set it down into the bottom of the new, slightly larger pot, then fill in around the sides and top with fresh potting mix. You can bury the stem up to the lowest true leaves at every stage of the potting on or transplanting process to create a bigger, stronger root system.

Hardening Off Tomatoes

If you’re growing your tomatoes outside, it’s essential that the plants are 'hardened off' before you plant them, which just means introducing them to outdoor conditions gradually. Start this on a mild day with little or no wind – there’s no quicker way to kill beautiful tomato plants than by putting them in a cold draught! At first, place them in a sheltered spot or cold frame for an hour or two before bringing them back indoors, then gradually lengthen the time they spend outdoors each day over the course of a week or so until they’re properly acclimatized. If you’re planting your tomatoes into a greenhouse or hoop house, they can be hardened off more quickly.

Determinate vs Indeterminate Tomatoes

Indeterminate (vining) tomatoes keep on growing until colder weather ends play in the autumn – they don’t have a pre-determined final size. They will produce fruits steadily throughout the summer. In the wild, tomatoes would naturally sprawl, but we want them to grow upright for the best results, which means we’ll need good supports.

Determinate (bush) tomatoes on the other hand do grow to a predetermined size – hence the name – which is usually up to around three feet (1m) or so. These more compact tomatoes are a great option for anyone growing tomatoes for the first time. Because determinate tomatoes aren’t vining, they’ll naturally bush out, which makes them lower maintenance. There’s no pruning required – just plant and leave them to do their thing!

Determinates also produce their fruits in more of a concentrated period, which is ideal if you’re hoping to gather a bumper harvest, all at once, to batch-cook sauces for the freezer or store cupboard.

How to Plant Tomatoes

Soil prep couldn’t be simpler – just spread a layer of well-rotted manure or garden compost to a depth of at least an inch (3cm) on the soil surface. You can do this any time in winter through to planting time. This will feed plants gradually over the growing season and does a lot of the heavy lifting to fuel all that growth. Plant tomatoes about 18in (45cm) apart in your prepared soil.

I’ve also had great success growing tomatoes and other fruiting vegetables in straw bales. It was like alchemy – transforming a lifeless, crisp-crunch dry bale into the perfect raised bed for crops. Great fun!

Tomatoes also grow well in containers filled with good-quality, all-purpose potting mix, perhaps given an extra boost with a small handful of a balanced organic fertilizer. Hanging baskets are fantastic, but you’ll need to watch them like a hawk to prevent them from drying out, so if you’re gardening in a hot, windy or dry climate they may be more bother than they’re worth.

With their demands for a warm, sunny position and well-drained soil met, you can bet your tomatoes will soon take off and put on rapid growth. Recent transplants can sometimes sulk – the leaves might roll up and even go a bit purple if the weather is less than balmy – but as soon as it’s consistently warm, they’ll soon recover and get on with the business of growing.

Staking and Supporting Tomatoes

Supporting or staking tomatoes is essential: it keeps plants upright, making the best use of space; it’ll dramatically reduce the chances of soil-borne diseases or fruits rotting on damp ground; there’ll be fewer pest problems; and looking after the plants is so much easier.

I use string supports for indeterminate tomatoes in the greenhouse because it’s convenient and very quick to set up – just suspend strong string from horizontal wires high up in the greenhouse roof. Weave the string support around the main stem from time to time as it grows to prevent the plant from flopping over.

Alternatively, or you’re growing outdoors, you could tie them to strong posts or battens. Bamboo canes can work but there’s a risk of them snapping under the weight of plants in full fruit, so proceed with caution! Tie the plant in at regular intervals so it’s well supported along the length of the stem. This will reduce the risk of weak spots and plants potentially snapping under the weight. You can use any soft material for this - twine, special twists, or even just strips of old rag.

Determinate tomatoes will need to be tied to a sturdy cane or stake as a minimum, driven down at least a foot into the soil to really anchor it in place, but they’ll also benefit from being grown in a tomato cage. That way, if they lean to one side under the weight of their fruits, they’ll be nicely supported by the cage and won’t suffer broken branches.

You can buy tomato cages, but it’s easy and cheap to make your own using cattle panels flexed into shape to give a diameter somewhere in the region of 18in-2ft (45-60cm). Use bamboo canes or sturdy prunings (e.g. hazel poles) as securing stakes to pin the cage to the ground.

How to Prune Tomatoes

Indeterminate varieties need to be pruned to get the best from them. It’s really quite simple - find the sideshoots, also called suckers, that form in the leaf axils (where the leaves emerge from main stem - shown in the picture above), and just nip them off between your finger and thumb. Inspect vines every few days so you catch the sideshoots while they’re still young and easy to remove. If they get a bit bigger, use a very sharp knife or pruners to cut them out to avoid the risk of tearing the main stem.

Removing sideshoots keeps vining tomatoes neat and tidy, so they’re easier to manage. And, because it removes excess foliage, it will also improve airflow around your plants, which is an important consideration to reduce the risk of disease.

When indeterminate tomatoes reach the top of their supports, cut or pinch out the very top growing point to stop plants growing any taller. This keeps plants manageable and focuses their efforts on developing and ripening those fruits. And it prevents plants from getting top-heavy and potentially snapping under the weight of all that extra growth.

However tall your plants are, pinch out the tips of plants a month before your first expected frost date to give them enough time to finish ripening before the cold stops them dead.

Determinate or bush tomatoes need little to no pruning because they grow to a specific size, then crop all at once. They won’t continue growing throughout the season, so they never really get out of hand. All that foliage gives plants maximum energy, which means maximum fruits – nice!

The only additional pruning I like to do – for both determinate and indeterminate tomatoes – is remove the lowest leaves. That’s because water hitting the soil can splash back up onto the leaves, and if they’re damp and congested with not much airflow they can act as an entry point to disease. By removing them, this leaves lovely clean and clear stems that allow air to move about more freely. It's also worth removing any damaged, diseased or yellowed foliage to keep plants neat, clean and tidy.

Improve Tomato Pollination

Tomatoes are technically self-pollinating, which is a big advantage when you’re growing them in a greenhouse or hoop house where there may be fewer bees about. Nevertheless, bumblebees can really help flowers to produce fruits, so do all you can to attract them.

Leave greenhouse doors and windows open as much as possible so bumblebees can get in and out, and entice them in by including flowers. French marigolds make a great companion flower to tomatoes thanks to their attractiveness to many pest predators too.

Too much heat can be another reason behind poor pollination, so opening windows and doors on very warm days will also help to moderate temperatures. If you find it gets too hot you could also try greenhouse shading to keep things cooler. Keep plants well-watered and mulched to preserve soil moisture.

I find that the simplest way to guarantee better pollination is to mimic the low, rumbling vibrations of the bumblebee by twanging on the supporting strings every time I’m in the greenhouse. If you’re growing tomatoes up canes, just tappety-tap on the canes to shake free the pollen. If you’re really keen you can rest an electric toothbrush on the back of each truss of flowers once they’ve opened to closely simulate buzz-pollination.

Watering Tomatoes

Recently planted tomatoes need a good soak to settle them in. Bathed in warm sunshine, tomatoes will quickly get going and grow strongly. At this point, plants will need between around one to two inches (up to 5cm) of water each week. You’ll almost certainly need to water your tomatoes – how much depends on where you’re growing them, what stage of growth they’re at and, of course, the weather.

Your mission, should you choose to accept it, is to keep the soil consistently moist, but never waterlogged. If in doubt, do the ever-dependable finger test – thrust a finger a few inches down into the soil and check how moist it is. If it feels dry, water. If it’s starting to get dry, give them a thorough soaking to make sure the water penetrates deep into the soil, rather than just wetting the surface. It's a good idea to use a watering can fitted with a rose to avoid blasting the soil away from around the rootzone. The important thing to aim for here is consistency to prevent problems with fruits splitting and blossom end rot.

Aim for consistency. Steady moisture helps plants grow without stalling, and prevents issues like fruit split, where a sudden rush of water after a prolonged dry spell can cause the fruits to quickly swell and the skin to split because it can’t keep up. Consistent watering also helps prevent blossom end rot, which is a common problem in erratically watered plants.

Using ollas can help provide this consistent soil moisture, even in hot weather. Plug up the hole in an unglazed terracotta pot then bury the pot in the soil next to a tomato plant. Fill it with water, and the water will gradually seep out to hydrate the soil as and when it needs it.

I like to mulch around plants to help conserve moisture too. Mulches also help to suppress weeds while preventing the soil from splashing back up onto the lower leaves. Dried grass clippings make a great mulch and readily available, but I’ve also used straw, which has worked beautifully.

Tomato leaves often curl up in very hot weather – that’s pretty normal, but if leaves are wilted in the morning, after the cool of the night, this is a sign that plants almost certainly need a good drink.

Feeding Tomatoes

Once plants come into flower it’s time to break out the liquid fertilizer. Good nutrition not only supports healthy plant growth, it will result in better tasting fruits too. Any product sold as a tomato feed will be great for this.

Having said that, a thrifty, money-saving tip that uses the power of nature is to make your own liquid feed using comfrey. Stuff lots of cut leaves into a bucket, fill with water – rainwater ideally – then cover and leave to stew for around a month. Dilute one part of the potent brew to two parts water. It’s beautiful stuff and is so easy to make – I thoroughly recommend it!

Preventing Late Blight on Tomatoes

As I said, try to keep the foliage dry when you water. Wet leaves can be a big risk for late blight, a disease I can only describe as ‘infamous’, and one that results in the catastrophic collapse of plants within a matter of days. Proper spacing, keeping plants dry, and choosing more blight-tolerant varieties will all help to prevent this devastating fungal foe.

I’ve chosen a blight-resistant variety for my outdoor tomatoes. Outdoor tomatoes will tend to get wet more often of course – you can’t prevent rain! – and they are more exposed to spores blowing in on the wind, so going blight-resistant’s a smart move.

Top Blight-Resistant Tomatoes

• Burlesque
• Cocktail Crush
• Consuelo F1
• Crimson Cherry
• Crimson Crush
• Lizzano
• Losetto
• Mountain Magic

Tomato Pests

Tomato hornworms are a nuisance for North American gardeners. These hungry caterpillars eat the foliage, weakening plants, so inspect your tomatoes regularly and pick off any that you find. You can add them to the compost heap where they won’t trouble your plants any more. They can’t sting or bite, so hand-picking is quite safe. If they’re a mega problem where you are, consider investing in a UV light because this makes them very easy to spot! Borage is also said to deter tomato hornworms, so it’s worth growing some. Borage is also a big bumblebee attractant, so this stunning bloomer offers a double-whammy of goodness!

Sap-sucking whitefly can sometimes prove a pest, especially when growing under cover. Flowers like French marigolds will help to attract pest predators such as hoverflies. But where whiteflies persist, try using a small hand-held vacuum to remove the worst of them every few days. You can also buy biological controls, like the tiny parasitic was Encarsia formosa, to hang up in enclosed environments like a greenhouse.

Harvesting Tomatoes

Relish the unbridled joy of perfectly ripe tomatoes – something that’s achingly elusive with shop-bought toms! Pick fruits only once they are fully ripe for the very best flavor and texture. You can often smell the aroma coming off your sun-ripened fruits, and cutting or pulling them free from the vine is nothing short of exhilarating!

Water plants in the morning then harvest your tomatoes in the evening if you can. By this time moisture levels in the fruits will have dropped a bit, further concentrating their flavor.

Try to pick fruits as close to eating as you can. If you need to pick a few days in advance, keep them on the kitchen counter rather than in the fridge – they’ll taste better that way. If you need to keep them for more than a few days, pop them into the fridge where they’ll store for at least a week, but be sure to bring them up to room temperature before enjoying them to give those lovely complex aromas a chance to recover.

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