My easy tips for growing the best tomatoes, with expert Holly Farrell

Tomatoes are a staple of the British garden, tempting us each spring with the promise of heavy trusses and sun-warmed fruits. Yet, for many, growing tomatoes can feel like guesswork.

To cut through the confusion, we invited Holly Farrell, author of The Tomato Grower’s Handbook, onto the BBC Gardeners’ World Magazine Podcast to give us her secrets to a bumper crop. Here's an edited transcript of exactly what she had to say.

Oliver Parsons (OP): Are tomatoes a good crop for beginners?

Holly Farrell (HP): Absolutely. If you’ve never grown anything before to eat, you are not going to start with cauliflower – it’s a bit complicated. But tomatoes, you can pick them, you can eat them straight off the plant, and they really are pretty straightforward and trouble-free to grow.

OP: What’s the difference between growing tomatoes indoors and outdoors?

HP: There is a difference, although with the caveat that your ‘outdoors’ varies hugely depending on where you are in the country.

An outdoor balcony or courtyard in the middle of a city is going to be very different from an outdoor plot on a windswept hillside in the Lake District or in Scotland. If you’re growing in the middle of a city, it’s almost the same as growing in a greenhouse sometimes. There are some varieties that will do better outdoors and some that will do better undercover.

Tomatoes come from South America originally, so they like a long, warm, sunny growing season to do well. If you can give them a sunny spot that’s nice and warm, that has good air circulation, and obviously water them, then really you should be laughing and picking loads of tomatoes.

Holly's top tomatoes…

#1: Gardener’s Delight

Type: cordon, cherry

“The nostalgia tomato. It does have quite a lot of side shoots, but it performs reliably, with lovely tangy, slightly sweet, red cherry tomatoes.”

OP: What equipment do you need to get started?

HP: The bare minimum would be to buy a packet of seeds and grow them in the ground, but obviously, lots of people don’t have ground these days. Sometimes it’s actually easier to grow things in pots, or you might want to grow your tomatoes in your courtyard or on your patio, which is sunnier and warmer than in your main bit of garden.

But really, you need some seeds, some compost or soil to grow them in, and a cane or stake of some description to tie them into if you are growing a cordon variety.

OP: What’s the difference between cordon and bush tomatoes?

HP: Cordon varieties, which are also sometimes called indeterminate varieties, are the ones that are going to grow tall and in a straight line upwards. They need tying in, and they won’t stop growing upwards until you stop them, and they are the ones that basically you grow them as a single stem. Those are the ones where you have to do the pinching out of the side shoots.

Bush or determinate are the ones that will basically have a few more stems and be a bit floppier. These ones are suitable for sprawling over the top of a pot, or even growing in a hanging basket, where the fruits can drape down the side of the basket.

Holly's top tomatoes…

#2: Crimson Plum F1

Type: cordon, Roma

“Plum tomatoes are the classic tomato used in tinned tomatoes that are sold in supermarkets. They have very few seeds and lots of flesh, and so they will cook down well into making a nice smooth sauce. It's a good blight-resistant plant as well.”

OP: Which type is best for growing outside?

HP: Bush varieties tend to be slightly hardier, a bit more blight-resistant on average. Also, they’re easier to cover outdoors because you can then put a cloche or a tunnel or something over the top of them to protect them from frost or heavy rainfall.

OP: Are beefsteaks and other varieties with larger fruits harder to grow in the UK?

HP: Yes, absolutely. If you’re going to try growing tomatoes for the first time, I would definitely recommend choosing a cherry tomato variety rather than the beefsteak ones, which are the big, ribbed, delicious-looking heirloom types.

Cherry varieties are the smaller ones. They’ll ripen faster, and you’ll get much more picking off them overall as well. If you are in a cooler, damper area, cherries are the best ones to go for.

OP: What are the essentials for sowing tomatoes?

HP: You need to start them off somewhere warm indoors. The first thing is to make sure that you’ve got enough space to sow your own seeds, because you can’t plant out your tomatoes until after the last frost, so you’re going to need a windowsill in order to first sow the seeds and then prick them out into larger pots and grow them on in larger pots.

If you haven’t got that space, think about whether you can grow seeds this year or whether it’s actually better to buy young plants from the garden centre or nursery.

Holly's top tomatoes…

#3: Tigerella

Type: cordon, bicoloured salad

“You can see the stripes from very early on the skin, then as they ripen, they end up as red and orange stripes. It has a really good tangy flavour to it, and also an AGM (Award of Garden Merit). This means the RHS have trialed it and found it to have performed really well in average garden conditions.”  

OP: What’s the best way to sow and grow on tomato seedlings?

HP: You can use multipurpose compost to start off. Just make sure you give it a sieve first, so you haven’t got any big lumpy bits. They’re a very small seed, so sow them at a very shallow depth and then cover it with a sheet of glass or a plastic cover just to keep the humidity and keep them warm and moist until they’ve germinated.

If you haven’t sown them in individual little pots, you need to be very careful when pricking them out. Hold onto a leaf, not the stem, and lever up from underneath the roots with a pencil or a plant label.

OP: When should you plant out tomatoes?

HP: Watch the weather forecast. There is really no substitute for just paying attention to your local weather. And of course, you’re going to harden them off before you plant them out anyway.

You will give them a chance to get used to the conditions outdoors, just by putting them outdoors for the daytime to start with, bringing them back in overnight, do that for a few days, then leave them outdoors overnight, and then you can plant them out.

Holly's Top Tomatoes…

#4: Sungold

Type: cordon, cherry

“Generally known as the cherry tomato to which all other cherry tomatoes are compared. The sweetness and the flavour of it are, they're just unparalleled. It's delicious.”

OP: What are the key tasks once the plants are growing?

HP: When you plant them out, you need to make sure you put your stake in at the same time. The two things now that you need to be doing are tying it into the stake, and also to be taking out any side shoots of cordon varieties. If you don’t take off those side shoots, you are going to end up with a really, really heavy plant that’s just going to fall over with stake and all. It’s diverting all that energy to those side shoots to grow new foliage when you want it focused on making those lovely tomatoes nice and ripe.

OP: How do you improve the flavour of home-grown tomatoes?

HP: The one thing that will stop you getting watery tomatoes when you pick them is to not overwater them. As the fruits start to ripen, you want to be tailing off your watering. So all throughout the growing season, you’ve kept a nice, even regular watering regime because that’s going to stop your fruit from splitting. At the end of the summer, when you’ve got those last lots of fruit ripening on the vine, that’s when you start tailing off your watering. That’s then going to really concentrate the sugars and the flavour in those tomatoes.

OP: Is there a trick to finishing off the crop as the season ends?

HP: A plant is going to keep on growing until it can’t grow any more, and it’s going to think, ‘I’ll just put out another truss.’ But we, the gardener, know different. We know that the end of summer is coming, and it’s not going to have time to ripen these new trusses of tomatoes that it’s putting on at the top. You need to be taking the top of the plant off completely. When it gets to the top of the cane, two metres thereabouts, sometimes three, but certainly no taller than that, because then all of the energy that it had been putting into growing will then go into ripening the existing fruit.

OP: What about pests and diseases?

HP: Tomatoes are remarkably trouble-free as a crop compared to many other fruit and veg crops that you can grow. They really don’t suffer that much from pest infestations or diseases, apart from blight.

I would just grow plenty of colourful flowers around them, especially if you’re growing cordons. Grow some marigolds; the roots exude a toxin, which puts off any soilborne pests from coming in. The flowers will attract pest predators such as hoverflies and ladybirds, and they will come in and they’ll munch up any aphids or whitefly that might be hovering around your crops.

OP: How do you know when to pick tomatoes?

HP: A tomato has got a little joint where it joins onto the truss, like a knuckle. If you lift the tomato with your thumb on the knuckle and lift up the tomato, it should snap away nice and easily. That’s a really good sign that it’s ripe to eat. If you are growing a variety that’s red, orange or yellow, wait until it’s developed the fullest colour before you pick it, because that’s when it’s going to be its most flavourful.

Holly's Top Tomatoes…

#5: Yellow Pear

Type: cordon, cherry/salad

“Apparently, the oldest tomato variety in existence today. A really vigorous plant. Grows well outdoors or indoors. And they're delicious as well.”

OP: And what can you do with unripe fruit?

HP: You can pick the truss or even the whole plant and hang them inside in a nice, warm place, and they should ripen. Ripening fruits like bananas and apples will help the tomatoes ripen if you put them close by. Even just on a sunny windowsill, they should ripen eventually. Or, of course, you can use them green and make chutney, or even green tomato jam.

OP: Should gardeners try saving their own tomato seed?

HP: If you save seed from the best-performing plants on your plot year after year, what you are essentially doing is a bit of natural selection. You are creating a particular strain of that variety that is particularly suited to your plot. You can only save seed from heirloom or heritage varieties.

To save tomato seed, scoop out the seedy innards into a glass of water, let them ferment on a windowsill for about three days, then wash them through a sieve, get rid of all the goo and the gunk, tip them onto a piece of kitchen paper, leave them to dry until they’re completely dry, and then you can store them for next year.

Holly Farrell’s The Tomato Grower’s Handbook is published by Bloomsbury, RRP £14.99.
To hear the whole podcast, click here.