Picture of Medwyn Williams

Medwyn Williams

Hello. I'm Medwyn Williams – eleven times Gold medal winner at the Chelsea Flower Show, Past Chairman of the Royal Horticultural Society Fruit Vegetable and Herb Committee and President of the National Vegetable Society.

Growing Your Own Vegetables – Tomatoes


Tomatoes must be about the most popular greenhouse crop of all, nearly everyone I know with a greenhouse grows a few plants. The main reason we grow our own is to try and achieve that flavour that still lingers on the pallet from years back.

Tomatoes must be about the most popular greenhouse crop of all, nearly everyone I know with a greenhouse grows a few plants. The main reason we grow our own is to try and achieve that flavour that still lingers on the pallet from years back. I can easily remember when I was a child being allowed by my father to pick a small tomato myself from a plant. The smell and the warmth of the  tomato in my hand, never mind the superb flavour, still lingers today and the only way I can really manage to get that taste back is to grow my own.

Planting in a Cold Greenhouse

Now is perfect timing to be planting your own in a cold greenhouse, in other words a greenhouse that has no heat at all in it. Tomatoes are a close relative to the potato, both are susceptible to frost so planting too early in a cold house can be extremely risky. Of course we may still get some frost even now but the thickness of the glass should be sufficient protection at this time of year to prevent a catastrophe. If you live in a mild area and have no greenhouse at all and you still fancy the taste and flavour of your own home grown tomatoes, then wait a few weeks until Mid May to early June when you can plant directly outside.

Planting Outside

You have two options that you can use when planting outside, if you are prepared to use some protection such as cloches, then you can plant out from Mid May but without any protection whatsoever it’s advisable to wait until the end of May to early June. Initially however tune in to the weather forecast and should ground frost be promised have a piece of fleece at the ready to cover them over. Always remember that only few of the varieties that you grow under glass are suitable for growing outside. Even though the Isle of Anglesey where I live is on the Gulf stream, we are susceptible to some really strong winds so I always recommend growing the bush varieties that need little if any support Tornado F1 is a round fruited high yielding thin skinned variety that has been bred for the British climate and Incas F1 is an early ripening continental type with plum shaped fruits.

Container Growing

Another type to grow outdoors, either in pots or containers, on your patio or in hanging baskets, are the small fruited types such as Tumbler and the newer Tumbling Tom Red and Tumbling Tom Yellow.  I can really vouch for the latter two as I grew them last year for my Chelsea display and was impressed with their vigour which makes cultivation easy. One word of warning however, don”t leave the hanging basket anywhere near you letter box, my postman took such a liking to the fruit that I had to move it elsewhere!


If you do have a go at growing them in containers or baskets, always use the right compost for the job such as the ready bagged tub and container compost. This type of compost will often have some gel incorporated as well as slow release nutrients to sustain growth through the early part of Summer. However I do like to feed my plants for optimum results and, Ideally, a liquid high potash tomato feed once the fruit are well set and turning colour will continue to maintain a high yield of fruit. It’s very important to remember that container grown plants will very quickly fill their pot, tub or basket with masses of roots so do water regularly. On hot sunny days at least twice a day is a must and even three time if the plant is in direct sunlight.

Growing from Seed or buying Plants

If you want to grow your own tomatoes then sowing them yourself will give you the most pleasure as well as the best plants. You can pot them on just when they need doing as well as giving them sufficient space on the greenhouse bench to prevent them from growing “leggy’. If you are going to purchase some plants do make sure they are sturdy and strong with a nice deep fresh green colour and about 9 inches tall. I have grown my tomatoes in various ways over the years and currently the one that gives me the best overall crop is by constructing a simple box on the greenhouse concrete floor. This consist of some old scaffold planks which allows a depth of compost of around 8 inches, this gives the tomato roots a good free run.


Plant the tomatoes reasonably deep so that extra roots will soon develop from the stem further enhancing the plant which in turn will reward you with increased yields. Don’t be tempted to plant them too near to each other they need plenty of room to develop properly. More importantly though they need plenty of air movement around them, when a tomato plant is in full stride it certainly has a lot of foliage restricting a god flow of air through the house. One of the main disease problem with tomatoes is Botrytis which manifests itself very often as small ghost spots on the fruit. Allowing plenty of air to get at the plants by opening up the roof and side lights as well as leaving the door fully open will go a long way to prevent this happening. As they grow the plants will need supporting, either by some strong twine suspended loosely from a taut wire to which you can wind the plant around or by using canes. I prefer strong canes which are pushed into the compost immediately after planting to which the main stem is tied loosely at regular intervals.

Gro Bags

Gro bags on their own are perfectly fine but they will need regular attention to watering right through the growing season. If you fail to carry out this task regularly and properly, then your tomatoes will almost certainly respond adversly to this at a later date when a black leathery patch appears underneath several fruits. This is called blossom end rot, a cultural problem which is a lack of calcium at the fruit end, rather than a disease; so after slicing the black bit off, you can still eat the tomato.  When you actually notice it for the first time, the plant would have been under stress three weeks prior.

Tomatoes easily move most nutrients around the plants, particulalry Nitrogen and Potassium; Calcium however, an essential element of tomato growing, is a different ball game. If tomatoes are not watered properly and get dry around the roots when in flower, the critical period being between 16 and 21 days after pollination or in other words after the little tomato has formed, the problem kick starts. When the plant is left dry it struggles to move calcium around to the fruit and will take it instead to the foliage first, leaving a lack of calcium within the fruit, hence the problem.

One of the problems with Gro bags is that you are enticed to grow three plants per bag and that in my opinion is too much, two per bag will give you a better crop. You can also grow them well in pots, in the past I have grown mine in second hand florist buckets which you can pick up cheaply, sometimes even for free, from most of the big florist outlets, particularly after Easter, Christams etc. Take them home and drill a few holes in the bottom and fill them with Gro bag compost. 


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