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How to Grow Greenhouse Tomatoes

Tomatoes can be grown in the greenhouse using several different methods. The majority of them attempt to get round the major problem of growing tomatoes in a greenhouse year on year - pests and diseases in the soil.

It only takes a couple of years growing tomatoes in the greenhouse for the soil to become "sick". The only solution is to remove and replace the soil or sterilise it using heat. Both are expensive and time-consuming. For this reason different cultural methods have evolved which only use a small amount of disposable soil / compost or none at all.


Possibly the commonest method of growing tomatoes in greenhouses is to use grow bags. These are simply plastic bags filled with a compost mixture. Cut two holes in the top and grow your tomatoes in the bags. This method certainly gets rounds the soil contamination problems because at the end of the season the grow bags are disposed of and new ones bought for the next season

Costs are on the low side; new grow bags cost relatively little and the cost of liquid fertilise is minimal. Given the amount of tomatoes produced using this method, it is also financially sensible, and the tomatoes produced are of course home grown and better tasting compared to shop bought tomatoes. Other main advantages and disadvantages are listed below.


Compost warms up quickly. Requires very frequent watering. Holidays will be a real problem.

Only small amounts of compost required. Salts can build up in the compost.

Eliminates many pests and diseases from the compost. Getting the amount of watering correct can be difficult. Plants can easily be waterlogged.

Nutrients and water levels can be well-controlled  

One variant of growing tomatoes in grow bags is to puncture the lower part of the plastic container. If the grow bag is on soil the longer tap roots of tomatoes which search out water may well then grow into the soil below and find a good supply of water. In some of the examples we have seen, this is repeated year after year with little or no introduction of pest and disease into the soil below. In essence, this method then becomes a variant of ring culture (see below).

One word of warning though about the above. If the depth of the grow bag is small, some of the fibrous roots may find their way into the soil below and this has the distinct possibility of introducing pests and disease into the soil. Keep this in mind if your grow bag tomatoes show signs of disease.


The key advantage of growing tomatoes directly in the soil is that you simply plant them without much preparation. The key disadvantage is that within a very short time pest and diseases will build up. The only solutions are to either remove the top soil annually and replace it with new sterile soil, or, to heat sterilise the soil each year.

The key good and bad points are summarised below:



Tomatoes grown this way taste better compared to other methods. Pests and diseases will be a problem after the first year. Soil should be replaced or sterilised annually. This is expensive.

The soil retains moisture well and therefore requires less watering. Soil is slower to warm up compared to other methods.

Other than growing tomatoes directly in the soil for the first year of a greenhouse, we do not recommend this method. Pest and disease accumulations in the soil will quickly become unmanageable.



Ring culure of tomatoes in a greenhouse This is not complicated and many greenhouse gardeners use this method, or a variant of it, without realising. Large plastic pots have their base cut out, and they are then placed directly on the soil, grit or gravel. Click the picture on the left to see an an enlarged version.

When the tomato plants are ready to be transplanted and all danger of frost is passed, the bottomless pots are filled with compost and the tomato plants are transplanted into them.

The theory behind ring culture of tomato plants in greenhouses is based on an understanding of their root system. Tomato plants have two types of roots: the roots near the surface search out primarily food and nutrients; the lower tap root searches out water. Click here for more information on tomato plant roots.

The standard method of greenhouse using bottomless pots (ring culture), tomatoes or other vegetables, is as follows:

1. Dig out the top 15cm / 6in of soil from the bed.

2. Replace the removed soil with 15cm / 6in of grit, gravel or similar material.

3. Place the bottomless pots on the gravel

4 Water the bottomless pots with liquid tomato feed twice a week

5. Water the grit (without liquid feed) at least every other day, more often in warm conditions.

6. At the end of the season, wash the grit well in running water and then store it dry for use next year.

The standard method above uses a 15cm / 6in layer of grit between the bottomless pot and the ground below the grit. The taproots will grow through the grit to reach the moisture in the soil below. Many gardeners have been using the above ring culture but without the layer of grit. The bottomless pot is simply placed directly on the soil. I know several greenhouse gardeners who have been doing this for many years with great results. It saves buying the grit, washing it each year and then storing it for next year. The choice is yours.

The advantages and disadvantages to bottomless pots (ring culture) are summarised in the table below:


Much cheaper than growing directly in the soil. Frequent watering is required.

Over-watering is unlikely to be a problem. Getting the correct level of nutrients can be tricky.

Compost warms up early in the year.  

Pest and disease problems will be avoided compared to growing directly in the soil.  



The above three methods cover the most common methods of growing tomatoes but there are others. Hydroponics, grafted and disease resistant plants, straw bale culture
are nut a few. However, the the main ones in the main article above are probably the only ones worth considering for the amateur gardener.