Extend the Tomato Growing Season
13 February 2023
Extend the Tomato season
Tomatoes are the Number 1 vegetable grown by gardeners across the UK. Any gardener who has a small greenhouse, polytunnel or even a sunny spot outside can grow tomatoes. You can even grow them in containers on the patio or in a hanging basket.
One of the main reasons for growing your own tomatoes has to be flavour. The taste of a homegrown tomato is miles apart from one purchased in a supermarket. How many times have you had the misfortune of buying tomatoes at a supermarket and when you get them home, they are tough and tasteless. The reason for this is simple, supermarket customers all want to pick out their own fruit these days, so the tomatoes they sell have to have thick skins and as a consequence they have very little flavour. Some are so tough you would need teeth like razor blades to bite into them. This is why growing your own is so important, and many of the modern varieties selected by seed companies for the home gardener are selected for their thinner skins, excellent flavour and high yields, plus the choice is endless.
With a little planning and a few extra sowings, it is possible to become almost self-sufficient in tomatoes throughout the year, which will limit the times you will have to sharpen your dentures and endure another dreaded supermarket toughie.
Let’s sort the Jargon
When you look though the various seed catalogue there always seems to be a lot of jargon or terminology when sorting out which tomato to grow. Here is a simple guide to what it all means.
Cordon (indeterminate) varieties mean they require supporting and their side shoots removed. Cordons are usually grown outdoors and stopped after 5-6 trusses.
Indeterminate growing makes more trusses when grown under glass.
Semi-Determinate varieties mean they make a vigorous bush, which requires some trimming.
Determinate (Bush Varieties) are predominantly self-stopping and require no side shooting.
Hybrids mean these varieties are F1 hybrids with good vigour, and usually some good pest and disease resistance bred into them, and are often commercial varieties or their cousins. You cannot save your own seed from a hybrid, as these varieties need 2 parent lines. Own saved seed will not come true to type.
Non-Hybrids means they are Open pollinated varieties, often quite old, although many amateurs are still selecting new ones. Seed saved from a non-Hybrid will grow the same as the original plant grown.
You will also see fruit sizes described as Cherry (small), Medium to Large fruits, Plums (oval shaped) and Beefsteaks (very large fruits).
When to sow tomato seeds?
It is possible to sow tomatoes at various times of year to extend the growing season, provided you have the correct growing conditions they require. Sowing little an often of as many varieties as you can accommodate in your glasshouse or on your plot will give you a wide choice or colours tastes and textures to enjoy throughout the year.
If you want an early crop for growing on in a heated glasshouse, then the best time to sow your seeds is the first 2 weeks of February. This early sowing can be
made with many of the greenhouse varieties including large fruited and cherry types. Remember you should only sow early if you have the right conditions to keep the young seedlings growing, so they don’t get any form of check. You will need both a heated glasshouse at a minimum temperature of 10C (50F) and heated propagator if you want to give it a try.
Mid-March to Early April
If you only have a cold Glasshouse to grow your tomatoes in then it is advisable to delay any sowings until now. But remember to get good germination you will still need to sow the seeds in some gentle heat in a propagator or on a windowsill indoors.
If you like growing Tomatoes outside on the allotment then they shouldn’t be sown too early, I find sowing the seed under glass in mid-April is ideal because the plants won’t get too big and start to spoil or suffer in their pots before they are planted outside. In most parts of the country, it is not safe to plant any tomatoes outside before the first week of June. When choosing outdoor varieties, some will perform better than others, I have always had success with Gardeners Delight
. However, with the treat of blight being more often these days it can also pay to grow an early maturing variety like Red Alert
as this matures before blight is around. Another alternative is to grow a blight resistant variety like Mountain Magic F1, Cocktail Crush F1 or Crokini F1
; all have become proven winners with the home gardener in recent years.
You may think this sowing is quite late, but in recent trials I have found that early maturing varieties can be sown this late. The best variety have I found is Sungold F1
, not only can you sow this variety for early indoors, a cold glasshouse or outside but sown at this time of year you will have fresh tomatoes ready to pick in early October often going on until the end of November, sometimes December. Obviously if you are making this late sowing, you must have a heated glasshouse for them to grow in through the end of the colder months of the year. Ideally your glasshouse should drop no lower than 10C (50F).
Hanging Basket Tomatoes
I love growing these varieties as they can give you an early crop and a wonderful display in a basket or container. Provided you have space to plant them up into their final container, once the plants are big enough, and you can keep them under cover in a heated or cold glasshouse, then you can sow these basket types anytime from February onwards. An early February sowing will grow well in a heated glasshouse and will have green fruit on the plants when you hang them outside in early June. These fruits will quickly start to ripen giving you an early outdoor crop.
I have sown these types as late as the 30th
of June. The plants will grow quickly and you can plant up baskets that can be hung outside in the summer then moved back under glass in the autumn. These will give you fresh fruits to harvest from the end of September until early October. I have had great success with early and late sowings from the varieties Cherry Falls, Micro Cherry, Tumbling Red and Tumbling Yellow.
How to Sow Tomato Seeds?
I like to sow my Tomato seed into 9cm (3in) Square flowerpots of moist seed sowing compost. I fill the pots with compost, then lightly firm it using a piece of wood the same size as the inner of the square pot. This leaves a small rim around the top of the tray, making a space to sow the seeds. I then water the compost so it is fully charged with water, using a fine rose on my watering can. Once watered I leave the pots to drain for approximately ½ an hour. The pots are now ready to be sown with seed. Tomato seed is quite large and easy to handle so it is important to try and sow the seed as evenly as possible. As a general rule I can sow up to 15 or 20 seeds per 3in(9cm) pot.
Once sown I lightly cover the seeds with a layer of fine grade Vermiculite, so the seed is covered to its own depth. I prefer to use Vermiculite rather than sieved compost as germination is better and you get a clean seedling, and less chance of the seedlings damping off.
Once sown I place the square pots into a heated propagator at 18-21C(65-70F), and I find under these conditions germination usually takes 7-10 days.
I find sowing in pots is a good idea, because often you only want a few seeds of each variety, plus it takes up less space in your propagator.
How to Grow Tomatoes?
Once the seedlings have germinated, I like to prick them out (transplant) before they get too large. I like to prick (transplant) my plants out into individual 4in (10cm) pots. The pots are filled with multipurpose compost, with a little Osmocote slow-release fertiliser added (at the manufacturers recommended dose).
When handling seedlings it is important to always handle them by their seed leaf and never by their stems. I always like to prick out my seedlings at the seed leaf stage, and I put them into the pots of compost so the seed leaves are just touching the surface of the compost. Some gardeners may think this is too deep, but if you follow this method, you will notice overnight the seedling will naturally lift slightly, making them sit slightly higher than the compost. Another reason for pricking out in this way is you will get a sturdier plant, as extra roots will also grow out of the tomato seedlings stem.
Young seedlings and plants should be grown on in a warm greenhouse at a minimum temperature of 50-60F(10-15C). Once the seedlings have become established and have two pairs of true leaves it is important to be careful with the watering. I will only water my young tomato plants when they really need it, otherwise you will end up with a monster. Tomatoes grow very quickly and if they have too much water as they grow when young they will soon become long and straggly plants rather than short and sturdy. I always like to keep my plants ‘on the rag’, which means I wait until the plants are hanging like a rag before I water them. Many a time I have had a visitor to my garden and they look in the greenhouse and say, I think your tomatoes need a drink, little do they know that’s the way I grow them to get strong sturdy plants ready for planting out.
The main reason I grow in this way in the early stages is to get a really strong sturdy plant, with its leaf joints close together. Remember the shorter your plants are when you plant them, the more trusses you will be able to carry on your plants before they reach the top of the greenhouse roof. Whereas a tall straggly plant won’t be as productive as it cannot carry as many trusses, before hitting the glass.
Whether growing under glass or outside my aim is to have a sturdy plant that is 9-12in (23-30cm) tall ready for planting into their final position.
If growing under glass either early in the season in a heated glasshouse or in a cold glasshouse later on
, the method I use for planting is the same. I am sure many of you will be surprised that I like to grow my plants in growing-bags.
I can here you all taking a sharp intake of breath and saying ‘Growing-bags’, surely not to get the best crop. Well yes, I do, but I slightly adapt my growing- bags. What I do is I flatten out each bag, after shaking it first to loosen up the compost. Then I cut out three holes in the top of each bag, using a bottomless 10in (25cm) pot as a template. Then the bottomless 10in pot is pushed into each hole in the bag about 2in(5cm) deep, and then each of the pots is filled with more compost from another growing-bag. I then plant a tomato into the top of each pot.
I plant them so the bottom 2 leaves are just above the compost. Then I take a 4in (10cm) flowerpot and cut two small holes in-between the three flowerpots in the growing-bag, this pot is then pushed into the bag on a slight angle. This pot allows you to water and feed your plants at the bottom of the bag, as well as being able to water and feed in the top of the 10in flowerpots.
The reason I use this growing method is because, you get a good depth of compost for your plants to root into. Your plants will produce roots from the top of the pots, and eventually filling the whole bag with roots, and the more roots your plants make, the stronger they will be, and the heavier the crop you should harvest. For many years I grew 4 Growing Bags (12 Tomatoes) in an (2.4m by1.8m) 8ft x 6ft greenhouse and had an excellent crop.
Once all my Tomatoes are planted, I tie a string loosely around the base of each plant and take it up to a pole that is fixed to the greenhouse roof and the strings are tied to the pole. This string is a quick and easy way to support your plants, and as they grow, I twist the plants around the string, so they support themselves. This method of support is a lot easier way of supporting tomatoes under glass, than tying them to canes.
Ideally your greenhouse should be kept at a temperature of 60F(15C) when plants are growing. As the plants grow remove any side shoots and twist them around the strings until you reach the top of the glasshouse. Then you can pinch the top out of the plant. This is usually after 4-6 trusses.
When the first truss has set, I like to give my plants a general liquid feed, something like Liquinure, to help build up a strong growing plant. After this initial feed I then change to high potash Tomato feed, which is given to the plants once a week from then on throughout the fruiting season.
It is also important to water your plants regularly in-between feeding so they are kept constantly moist, but not too wet or dry.
The plants I grow outdoors are grown in the same way in their young stages from the later sowing date. Then they are planted outside once all risk of late frosts have passed, which is usually the first week of June.
I like to plant into a well-prepared soil in open ground on the allotment, with each plant tied securely to a cane or stake. Tomatoes can be quite hungry so, if possible, the soil you have chosen should have had plenty of organic matter added to it last autumn. Prior to planting I like to give the soil a dressing of Growmore fertiliser at 60gm per sq. m (2oz per square yard).
If you have a sunny spot in your garden and you wish to grow some tomatoes outside you can grow them in large 10in (26cm) pots filled with growing-bag compost. Then put a cane to each plant, and tie each plant to it. This way you can grow a successful outdoor crop of Tomatoes without taking up valuable garden soil.
You can then side shoot and feed your plants in the same way as if grown under glass.
For Bush Tomatoes
, these can be grown very successfully on the allotment or in pots or large containers on the patio. The thing to remember with bush varieties is they require no side shooting, so are ideal if you are always short of time or space, as they do not take up as much room but are still very productive.
Hanging Basket Varieties
grow very well in pots or baskets and are treated like bush varieties, again with no side shooting necessary. I like to plant 3 plants in a 14in (36cm) basket filled with growing-bag compost. Remember to always hang your baskets in a sunny position to get the best crop. Tomatoes grown in Baskets and large pots will need regular watering and feeding as they can dry out very quickly on hot days. Growing Tomatoes in Baskets is great for those gardeners who are limited for space or if you want a very early crop.
What can go wrong?
The Most Common pest for Tomatoes is glasshouse whitefly. This can be controlled by spraying with a suitable insecticide that can be used on tomatoes (always check the label on the bottle). Another method of control is the biological
Control. You can introduce the minute wasp called Encarsia formosa that will feed on your Whitefly eggs. This will keep the whitefly down to a manageable level. For this method of control to work successfully you have to accept, that you will have a small percentage of whitefly still in your glasshouse, but not enough to cause any problems. If you don’t have any whitefly the wasp has nothing to feed on and will die. Encarsia formosa are available from many mail order companies and are sent out at set times of year to help you get the best possible crop protection.
Tomatoes sometimes get fungal diseases like grey mould and leaf mould. These are most common in humid, poor ventilated glasshouses. Botrytis also occurs if leaves or stems are damaged or scared whilst side shooting. Always remove damaged or yellowing leaves immediately. If you get bad attacks of Botrytis then you can spray with a suitable fungicide, but in most cases is unnecessary.
Another common problem in recent years has been potato blight that attacks tomato leaves in the same way, as they are both the same family. This is often more common on crops grown outside, but can occasionally also affect indoor grown crops. Blight usually appears when the weather conditions are very warm and humid. Blight shows their symptoms on their foliage first in the form of brown or pale spots, and then eventually the fruits turn brown and unsightly as well. Prevention is better than cure with blight, so spraying with a suitable fungicide when blight conditions are around helps. If you are growing Tomatoes outside, you can put up a plastic cover over the top of your plants this will help stop any water splash on your plants as this can accelerate the spread blight during blight conditions. You could also grow one of the Blight Resistant varieties like Mountain Magic F1.
Lots of gardeners find their crop suffers with Blossom end rot on their fruits, especially if growing the larger fruited or beefsteak types. Poor watering of your plants often causes this, because if your plants are allowed to become very dry, then wet then dry again, instead of being kept evenly moist, this blackening at the base of the fruit may occur. This happens because the lack of water stops your plants from
taking up enough Calcium, and calcium is very important to the development of your fruit.
Sometimes if you are growing one of the thinner-skinned Cherry tomatoes you can get a lot of fruits that develop split skins. This is also often caused by infrequent or over watering, so it is important to get the correct balance otherwise you will be using these split fruits in soups or drinks rather than in your salads.
Occasionally you get fruits with Green back on the shoulders of the fruit. This is more common on older varieties like Ailsa Craig. It is often caused when the fruits get to warm when grown under glass in small greenhouses. The way to help prevent this problem is to give your glasshouse a light shading with coolglass or fine green netting to soften the sunlight rays or grow a more modern green back resistant variety like Shirley F1.
Less common problems are Magnesium deficiency, which is shown up by a yellowing mark in-between the leaf veins, on leaves near the base of the plant. Giving each of your plants a pinch of Epsom salts and watering it into the compost can soon overcome this problem.
Tomato Mosaic virus is very rarely seen these days, as you can grow TMV resistant varieties now.
Good enough to eat
When growing tomatoes, I am always amazed how quick fruits ripen. One day you will see just a few fruits starting to change colour, the next there will be a basket full ready to harvest. As the fruits ripen gently twist the fruits, so they come away cleanly from the trusses with the calyx still attached. Once picked wash your fruits in cool water and place them in the bottom of the fridge, you can’t beat the flavour of home-grown tomatoes, their delicious!
Sungold F1 -
produces a heavy crop of thin-skinned rich orange fruits of the sweetest flavour and suitable for sowing and growing early or late under glass or as an outside crop.
Sweet Million F1
– a heavy crop on long trusses with juicy sweet shiny red, bite sized fruits. Best-grown under glass.
- An RHS AGM winner, British Bred, heavy cropper with long trusses of super sweet bitesize fruits.
– An old favourite produces long trusses with sweet tangy red fruits. Grows well under glass or outside.
- Unusual dark chocolate-coloured fruits on long trusses with a cross between a sweet and Smokey flavour. Grows under glass or outdoors.
– a Unique deep pink, very aromatic cherry tomato, tasting of a blend of summer fruits.
– A vigorous red cherry that not only holds well without splitting but also shows good Blight resistance.
– Produces Several large trusses of deep red fruits, best grown under glass.
– Ideal variety for beginners, producing a heavy crop of high quality well flavoured fruits. Suitable for growing under glass or outdoors.
– A very early cropping variety with unusual brightly coloured striped fruits and a rich tangy flavour. Suitable for indoor or outdoor growing.
Mountain Magic F1
– One of the best for Blight Resistance, medium size fruits, full of flavour. Superb outdoors
Y Ddraig Goch F1 (Red Dragon)
– Outstanding quality rich red fruits with a large calyx, good flavour and long-standing ability. Good for Exhibition.
– a Tasty big beefsteak with fruits up to 425g. Large and meaty with few seeds, perfect size sliced for a sandwich.
Orange Wellington F1
– Unusual Orange fruits, bursting with flavour.
– Possible the largest tomato ever, capable of producing 700g -1kg fruits with excellent flavour.
– Nearly seedless with a pleasantly different flavour, bred for ketchup and soup. Best crop under glass.
– Large Plum shape fruits ideal for cooking or making sauces.
– A long Plum with good resistance to blossom end rot. Supper flavour and virtually no seeds in the fruits.
– The earliest maturing outdoor bush with fruits that often ripen before blight appears. Superb flavour.
– Dwarf stocky plants produce many trusses of crimson fruit. Excellent grown in containers.
Tumbling Tom Red
– Perfect for baskets or containers producing a heavy crop of red cherry fruits.
Tumbling Tom Yellow
. The same habit as Tumbling tom Red but has attractive golden yellow fruits with a slightly sharper taste.
– Stunning in a basket, capable of producing hundreds to thousands of teeny super sweet red fruits.
– Early fruiting Deep red cherry fruits of exceptional flavour. Very prolific in baskets or containers.
By Andrew Tokely
Back to the Blog