How to Grow Tomatoes

  Gardening chat about growing your own veg often turns to the wonders of home-grown potatoes and tomatoes, but the two are very different crops to grow. Potatoes are much easier, and need little attention, (see growing potatoes ) and tomatoes are the opposite; time-consuming and more difficult.  When growing Tomatoes they need attention throughout all of the growing season starting with potting on, removing side shoots, thinning out the leaves as the plant matures, and as the fruits form, regular feeding and watering. Come harvest it is so rewarding to pick fresh sweet tomatoes straight from the vine and eat them. To me, summer is the smell of tomato vines.

 One advantage when growing Tomatoes  is that they are ideal for growing in containers, in fact they are usually grown in pots and grow bags, although this can make it more difficult to leave them unattended for long periods, such as holidays. Tomatoes growing in containers like all container grown plants are prone to drying out if unattended. If you are thinking of growing tomatoes you need to work out how to keep them watered during summer holidays. It is very disappointing returning from a lovely holiday to find your tomatoes plants suffering from drought. In the summer, if it is warm, tomatoes need watering several times in a week and if hot, daily attention. A gardening friend or neighbour is good, also there are also some effective irrigation kits on the market.   

    When growing tomatoes outside you need a warm, sheltered spot  and if you don't have this in your garden Tomatoes are best grown in a greenhouse. Tomatoes are a very rewarding crop and fun if you like growing veg. In the growing guide below are helpful tips to ensure you have a successful, tasty crop of tomatoes. Tomatoes are not frost hardy so if you intend to grow tomatoes outside, only plant out when all risk of frost has passed. As a rule of thumb in the UK last frost will usually be at the end of May/first week of June. Even thought plants are sold in the garden centers from Feb - May do not plant out, treat them like a bedding plant and wait until the conditions are warm. Tomatoes grown under glass will fruit earlier and be less prone to blight.

Advice and tips on growing vegetables .

10 top tips on How to to grow tomatoes

There is more information about all these tips below;  here is a quick guide checklist:-
  1. Grow a variety of tomato most suited to your growing conditions. For example if growing tomatoes outdoors pick a variety which is blight resistant, beefsteak tomatoes take need a lot of sun and light whereas smaller cherry tomatoes will ripen sooner if you want an earlier crop. 
  2. Pot on 2/3 times during the growing season.
  3. Harden off before planting outside
  4. Most, most, most important feed and water regularly. 
  5. For upright tomatoes, these are tomatoes with one single stem as compared to bush tomatoes and are also know as  Cordon tomatoes,  remove the side shoots to ensure there is just one central branch.
  6. Also for upright tomatoes thin foliage throughout the season or the plant will be all leaf and less fruit.
  7. Start feeding when the flowers appear
  8. Once the plant has 3 sets of flowers stop off the top growth.
  9. Stake and tie the plant to support it especially the fruit
  10. At the end of the growing season cut off vines and bring indoors to ripen.


Success with tomatoes a detailed handy guide full to tips and information about growing tomatoes 

How to grow tomatoes from Seed

The growing season for tomatoes varies a little depending on where in the UK you are growing your crop. The season is longer in the south of the country, where you can often start germinating from seed as early as late February, with good light conditions and grow through until around late October/early November. Tomatoes need good light and heat to grow well so  if you are not sheltered it is best to start tomatoes off indoors. .   

Tomatoes are easy to get started from seed. Place two or three seeds into a small pot filled with fine compost, cover the seeds with a light sprinkling of compost and they will germinate quickly provided they are kept warm and covered (with polyethylene or propagator) until they have germinated. Tomatoes need a temperature of around 21 C to germinate.

Early in the year when conditions are cool, it is best to germinate in a propagator to create a warm, moist atmosphere. The seedlings will emerge after a few days and once the seedlings emerge, uncover and reduce heat. If seedlings (of any plants, not just tomatoes, ) are left too long in a propagator the heat and warm moist atmosphere will make the seedlings floppy. It is important as soon as the seedling has fully emerged to remove the pot from the propagator, and keep frost-free.

When deciding which variety of tomatoes to grow from seed, think about the size of the tomato. The large beefsteak varieties will need a longer, sunnier growing season to ripen than the smaller cherry type which, depending on where in the country you garden, and the amount of sun and light levels, may be an important factor in deciding which type to grow. This is particularly true if growing tomatoes outside, as opposed to in a greenhouse which provides a warmer more sheltered growing environment. As with all plants grown from seed they can become leggy if light levels are poor. This is because the seedlings stretch towards the light, and if the seedlings are in grown in conditions where the light is uneven, or low light conditions, it will produce poor seedlings for potting on. Early in the year tomatoes grown inside, and in particular on a window sill, can easily become leggy. If you do grow on a window sill where the light is predominately from one direction, turn the plant very regularly. If the seedling turns out leggy, don't throw it away, but when potting on plant it deeper to overcome the problem. 

Tomatoes seeding in early spring will come to fruit later in the summer, depending on the weather conditions producing fruit from late July on wards and will be finished by November when they should be composted. In our climate tomatoes are an annual plant growing for just one season.

Video advice and tips on successful germination from seed.

Potting on tomatoes

When growing tomatoes as the plant grows and matures, it will need to be " potted on" which means re potting into larger pots. In the growing season, you may need to do this about 3 times from the small plug plant stage, until the tomato plant reaches maturity, and is large enough to go into full size pot or grow bag. 

It's tempting to save time and put the tomato into a larger pot at the beginning, but this  not ideal.  If you put a small plant into a large pot or grow bag, it will not thrive. Pot the tomato plant into a slightly larger pot doing this 2/3 times until planted into its final large growing container. 

It is a good idea to plant tomatoes deep, especially if your seedling is a bit on the weedy side. The only exception is in respect of grafted plants.  The last pot into which you plant your tomatoes as the growing medium for the rest of the summer, should have a diameter of between 20- 30 cms, and the larger the better. If you are growing a grafted tomato plant it is really important to ensure when re-potting that graft union is above of the soil. 

Grow bags are often promoted as a good growing medium for tomatoes. Whilst they are convenient, the problem is the depth of compost is shallow. This causes problems when watering as the water has a tendency to run off. Also, the bag tends to flatten out as a result increasing the difficulty in watering. For tomatoes, regular watering is absolutely essential and irregular watering impairs the flavour and can cause the skins to split later in the season. It is important to get the water to the plants roots. To increase the soil depth which will help with the watering problem, use tape to strap up the bag, or supports as in the image left, to make it more rounded. You need to get the plants to a reasonable size before putting into a grow bag as in the image. 

You can grow tomatoes in a greenhouse or outside,  but tomatoes do need a warm, sunny sheltered spot and not all gardens or parts of the country enjoy these conditions. An alternative is to grow in a greenhouse or poly tunnel which creates an ideal growing environment for tomatoes, and offers protection from blight.  Blight can be a real problem and is a rare visitor on greenhouse grown tomatoes. If planting out side pick the most sheltered spot in your garden such as sheltered sunny patio.

When potting on a tomato plant is a good time to add a water bottle for effective watering, see below.

Short video showing how to pot on tomatoes 

Hardening off Tomatoes

  If you are going to grow your tomatoes outside you will need to "harden off" the plants, which means getting the plants used to the cooler, less clement conditions outside, as opposed to controlled conditions in a greenhouse, lean to or indoors where the seedlings have been previously grown. If you intend to grow outside, in late spring you will need to place the plants outside, starting on days when the weather is at its best placing the plant outside for increasingly longer periods. Only leave outside overnight once the risk of frost has passed. 

 Upright tomato plants get quite large, around 1.5 m (5 ft+ ) so they need plenty of support, especially later in the season when the branches are heavy with fruit and can easily to snap. All upright tomatoes need support and to be tied into canes to support the plant and the fruit. The image left illustrates the wrong way to tie in a tomato plant. When the tie was put on, it probably looked Ok but as the plant has grown, the tie has tightened and damaged the stem. To avoid this use soft ties, check regularly and loosen as the plant grows. I really like raffia as a plant tie, it's very strong and looks natural.   

Temperature wise tomatoes are less than happy below 15 C at night, and below 10 C could damage the plant. If it turns unexpectedly cold protect the plant with a fleece. Equally too hot and the plants are not happy ideally not above 35 C. This means on very warm days it is essential to ventilate the greenhouse and perhaps spray the floor with water if it is very hot to cool the greenhouse down.  It follows from this that  almost all conservatories in the summer months are too hot for growing tomatoes. 

Feeding and Watering Tomatoes

how not to water a tomato plant
effective watering using a cut down bottle

    It is essential for a good crop of sweet tomatoes that they are watered and feed regularly, and this is true whatever type of tomato you are growing. All types of tomato plants need to be watered regularly and increasingly as the tomatoes form and get larger. If you are growing under glass / greenhouse tomatoes will need watering daily on warm days to make sure plants do not dry out.If the plant dries out this can cause damage to the plant, and can cause the fruit to have tough split skins, and a less sweet flavour. One of the aims of growing your own tomatoes is to have sweet tasting fruit; irregular watering will impair the flavour. Regular feeding is equally important and feed with proprietary tomato feed as soon as the first flowers appear, and feed regularly throughout growing season. The bottle will give instructions to ensure the correct amount of feed to water ratio. 

The image left shows how not to water a tomato plant. It is important to try and avoid splashing feed or water the leaves which can raise the chances of disease.

The image right shows an effective way to ensure the water goes to the tomato roots. Cut the bottom off a plastic water bottle and sink it into the pot when you are potting on the tomato. This enables you to funnel the water down to the roots away from the leaves.

How often to water tomatoes? There is no rule of thumb, plants need less water when they are small so as the plant grows water more regularly. Do not let the compost dry out and the warmer it is the more water the plants need.

Growing Cordon Tomatoes the Upright types

Upright tomatoes are know as Cordon Tomatoes. As the name suggests they do not bush but grow upright with a single stem and they have additional requirements which include stopping off the growth, pinching out side shoots and thinning the foliage- detailed below.  

  Upright tomatoes need more attention mainly because they grow taller and are very vigorous. Later in the season, around September it is necessary to "stop off" the tomato plants. This means to pinch out the growing tips at the top of the plant and stop the plant growing up any further. If you don't stop the plant growing up wards, it will put all its energy into producing more growth and leaves at the cost of flowers, which become the fruit. 

 Stop off at the growth tips when the plant has 3-4 (outside grown) and 4-5 (greenhouse grown) trusses which are layers of flowers. Tomato plants are vigorous, and produce a lot of growth and leaf in full season. It is time-consuming but essential to take off some leaves and thin growth regularly. Continue taking out the growing points as the plant will strive to keep growing. This means once you have cut off the top of the plant to stop it growing you will need to do this again, and again, as it will keep trying to grow through the greenhouse ceiling.  

Because Cordon tomatoes grow so tall, they need support. There are commercial metal supports as show above the grow bags. However simple bamboo canes and wooden stakes will suffice. If the fruit is heavy or large you may need to support it with extra ties, and again raffia is very good for this. 

Pinch out tomato side shoots

  As the plant grows it is essential to remove all new side shoots, which appear at the junction between the upright stem and the branch. Look at the plant main stem and where the branches grow, any little growth appearing at the junction of the upright stem and the branch needs to be removed. 

In the image my finger is pointing at the side shoot which grows at the junction. During the growing season the plant will produce side shoots at the junction of the plant and stems; keep removing them. You are containing the plant's growth by the removal of these shoots. Otherwise the plant, which is very vigorous, will produce a mass of leaves and shoots. By restricting growth it will produce more fruits. 

Because it is really important here is a short video How to remove side shoots 

Thin out Foliage

  Later in the season, if you have time, it is a good idea to thin out the tomato foliage so the plant puts energy into fruits and not more and more leaves. This needs to be done as soon as the flowers appear and carrying on as it fruits. The plant shouldn't have a mass of leaves on it. Be bold, cut them off. In the peak of the growing season I remove lots of leaves each weekend when checking the tomatoes. This also aids ventilation, which helps to reduce the risk of diseases. By the time there are several trusses of fruit, the leaves should be well thinned out.  

Lack of flowers on Tomatoes

The flowers on tomatoes are very important as they become the fruit, i.e the tomatoes so the more flowers the better. A lack of tomatoes can be caused by poor pollination. The flowers need to be pollinated to produce the tomatoes, and this is more of a problem for tomatoes grown indoors in greenhouses and poly tunnels. Outside, nature does this by the presence of pollinating insects, bees. This means it is important to open up the greenhouse doors, windows and vents to let the bees in to do their work. Commercial growers with large poly tunnels and glass houses will import bees to do this job. I have seen commercial growers in Iceland growing tomatoes in the depths of winter, utilising the thermal underground heat, and importing boxes of bees to fly around and pollinate.  

A lack of fruit can also occur during poor summers, if it is persistently wet and cold and the pollinators are not able to fly around as much due to the adverse weather conditions. 

A foolproof way to ripen tomatoes

  There is a perception that tomatoes can be difficult to ripen once the main summer is past. Often in October as the nights are drawing in the light levels are dropping, the plant is slowing down and the fruit doesn't seem to ripen. The tomato plants still have loads of green tomatoes and chutney isn't the solution.When it's turning chilly, depending on Autumn weather, cut the tomatoes off the plant on the vine and lay them on cardboard/newspaper in a spare room, conservatory or a dish on sunny window sill and they will ripen. The Sunday Gardener has used this simple method to ripen tomatoes for several years without fail. The vines need to be somewhere warm, and the fruit will ripen . This method was found to be fool-proof when moving house one year in early Autumn and it was not practical to move the tomato plants, and so the tomato plants had to be cut down. The trusses of fruit were cut and left on cardboard in a warm place, and 80%+ ripened

Golden rules for Growing Tomatoes

  Watering is really crucial: do not let the plants dry out. For best results feed regularly as soon as the first flowers appear. Keep an eye on the plants, thin out leaves and take off side shoots. Don't give up on them: Tomatoes will crop in greenhouse until November after which cut the vines and leave somewhere warm to ripen. To avoid diseases, if growing under glass make sure there is good ventilation and air circulation, and avoid splashing the leaves when watering. Click here for  More information about growing tomatoes including different types to grow and tomato diseases, and blight. 


The Sunday Gardener has written  a comprehensive guide to growing tomatoes " Success with Tomatoes" 55 pages, and 23 illustrations. Each chapter is full of information, tips and a step by step guide to growing tomatoes with a key point summary and checklist.  Available in e book format and paperback, you can keep it on your phone or tablet for easy reference when in the garden or greenhouse. It is available on Amazon and you can look inside before you buy; £1.99 as  an e book £4.99 in paperback.