Tomatoes, named by the Aztecs, tomati, have been bred from some 10 wild species native
to Ecuador and Peru. Brought to Europe by the “Conquistadors” in the 16th century,
many of the tomatoes were yellow. Nowadays, they come in all shapes, sizes and colours,
from green through to black. There could be thousands of varieties in existence,
though there are probably only hundreds available commercially.
They contain lycopene, which helps to protect against heart disease. If you have
arthritis, it is suggested that the yellow types are better for you.
Easy and rewarding to grow in a cool greenhouse, if you choose the right varieties.
I generally prefer to grow the “cherry” types, as they fruit earlier and they can
have fabulous flavour, better than anything you can buy. Not only do different varieties
of tomato taste completely different, but personal taste preferences come into play.
The taste of tomatoes, is made up of various components such as Sweetness, Acidity,
and whether they have a clear and clean taste or a “muddy” taste. My preference is
for high sweetness, high acidity, combined with a clean and clear taste, such as
in “Sungold”, a regular winner of taste tests.
Start your chosen seeds in heat in March in small pots filled with any good compost.
Reduce the heat and grow them on in a well lit position to prevent them getting too
leggy. Plant out in a cool greenhouse towards the end of April, provided the weather
Tomatoes grown in a greenhouse will probably be planted into grow bags, when 2 plants
to a growbag is ample. There are other methods used such as ring culture, and growing
in large pots filled with compost. See Greenhouse Crops for specific cultivation
Most tomatoes grown in a Greenhouse will be indeterminate, and require to have all
side shoots pinched out, leaving the flower shoots of course! Pinch out the leading
shoot when it reaches the roof of the greenhouse, or when some 6 flower trusses have
formed. Train the leading shoot up a cane or a length of twine, attached to both
the roof of the greenhouse and tied underneath the grow bag. As the tomato trusses
swell, the total weight of tomatoes on the plant can become so large that the tomato
main stem can buckle or break. To avoid this happening, tie additional twine round
the top of the stem and support it from the greenhouse roof.
For growing tomatoes outside, I would choose quick maturing, bush types, to try and
reduce the problem of blight, but do not transplant them outside until all danger
of frost is over in your area, in June. Even then, continue to provide cloche protection
in the North for the rest of the month.
Warning. On no account plant out these sub-tropical plants before the last expected
date for frost in your area. This could be mid May for the mildest areas such as
Southern coastal areas, and early June in the North of the UK. Even then, provide
cloche or fleece protection for the first few weeks as cold nights and winds will
cause plant damage. Gardeners are regularly caught out by late frosts occurring during
the traditional cold period known as “The Ice Saints”, usually just before mid May.
Remember, one night of a late frost will kill your sub-tropical plants!!
Tomatoes require a high potash fertilizer which is usually provided by a proprietary
liquid preparation. Some gardeners make up their own organic concoctions, but the
difficulty is knowing how much dilution of the liquid in water is required. It would
be quite easy to burn the roots of the tomato plant if the concentration is too strong.
Pests and diseases.
The worst disease is blight, especially for outdoor tomatoes, where you are quite
likely to suddenly loose all your plants if the conditions of temperature and humidity
are suitable for Blight. If you see your potatoes being attacked by Blight, assume
that any outdoor tomatoes will be affected as well.
The weather conditions that are likely to lead to an outbreak of Blight, are known
as “Smith Days”. This is when there are two consecutive days where the minimum temperature
is 10 C or above. In addition, for at least 11 hours each day the relative humidity
is greater than 90%. In other words, two days of particularly hot and sweaty weather!
You may have no alternative but to spray against blight with “Dithane 945”, though
I am not keen on its use. Some degree of control can be obtained by erecting a shelter
above the tomato plants by using a polythene cover, which prevents Blight spore laden
rain water from falling onto the tomatoes.
It can also affect indoor tomatoes if the humidity and the temperatures are too high,
especially in the late Summer and Autumn. In the greenhouse, remove any affected
leaves to try and limit its spread.
Mildew can be a problem in greenhouse culture. An increase in ventilation can help
to control it, or spray with a fungicide. Also snap off any leaves that are affected
to stop the spores spreading in the air currents.
Splitting of the fruits is usually caused by erratic watering. It is important to
make sure that the compost is not allowed to dry out and then made very wet. As home
gardeners are more likely to grow choice varieties of tomatoes with thinner skins,
this can be a problem.
Blossom end rot, where the blossom end of the fruit starts to rot, has a similar
cause. However, some varieties of Tomato seem to be particularly prone to this problem.
For instance, the variety “Black Russian” is prone to Blossom end rot, while I have
never seen it on “Sungold”.
Greenfly, red spider mite and whitefly are all serious pests on tomatoes, sucking
the sap and spreading virus diseases. Pay particular attention when bringing young
tomato plants into your greenhouse and make sure that they are not already infested
with these pests. If you see any signs of infestation, spray the plants thoroughly
with a suitable insecticide. See Greenhouse Pests for suitable treatments for the
control of such pests.
Tomatoes are best used fresh, and should be picked when each fruit is ripe and just
starting to soften. Depending on the variety, in addition there will usually be a
colour change in the fruits. To minimise the danger of the fruit splitting, the individual
tomatoes should be gently snapped off their stem at the first knuckle joint above
the fruit, leaving the green calyx and about a cm of stalk attached to the tomato.
This works well for cherry tomatoes, but you may well have to cut off bigger tomatoes,
to minimise splitting.
You may be surprised to learn that a bunch of Tomatoes does not naturally ripen all
at once, as sold in shops as “vine tomatoes”. They achieve this affect by using a
variety that has tough skin, and has an ability to prevent the ripe tomatoes from
going soft. Even so, they usually have to cut off and waste the green end tomatoes.
Naturally, tomatoes ripen in sequence from the main stem to the end of the bunch,
and need to be picked in sequence, as and when they are ready.
In times of a glut in the Autumn, consider bottling or freezing them as a puree,
using them for soup or making a tomato pickle or chutney.
At the end of the growing season, say November in the cold greenhouse, you are quite
likely to have quantities of green or semi-ripe tomatoes still on tomato plants,
that are never going to ripen in those conditions. However, if they are carefully
picked and placed on shallow trays in a sunny windowsill in your house, most will
eventually ripen, even if it takes till January. Nothing like your own tomatoes in
the middle of Winter! You can use the same trick to try and improve those ghastly,
insipid, shop-bought tomatoes available in the Winter.