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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.

Maximising your crop of Tomatoes and Cucumbers


There are two crops inside the greenhouse that need regular attention now if you are to get the optimum crop from them -Tomatoes and Cucumbers. Most gardening books will tell you that to grow tomatoes and cucumbers well they should be grown in separate greenhouses as they require different conditions.

Two crops inside the greenhouse that need regular attention now if you are to get the optimum crop from them are Tomatoes and Cucumbers. Most gardening books will tell you that to grow tomatoes and cucumbers well they should be grown in separate greenhouses. The theory behind this is that the cucumber grows superbly well in a moist warm damp climate, so humid that when you walk into the greenhouse on a nice sunny day, your spectacles will steam up. Also, cucumbers are prone to attacks from the Red Spider Mite which spreads it’s fine silky webbing across the leaves and stems and the best cultural control is to keep a moist or humid atmosphere. Conversely tomatoes, if grown under the same regime as cucumbers could be prone to disease, in particular Botrytis.

Air Movement

This manifests itself during this month if there isn”t enough air movement within the growing structure. To alleviate this problem, without reverting to the use of chemicals, start off by planting at a lower density so that the plants don’t squash up against each other causing the disease to spread quickly and infecting all the plants. Make sure there is plenty of air movement in the house by leaving all the windows open as well as the door. Another important consideration is to water first thing in the morning so that by late evening the air around the tomatoes is dry with less risk of the disease spores affecting your plants. Always remember that the biggest carrier of disease in you greenhouse is probably the water itself.


Both plants however can be grown to perfectly adequate standards in the same house, many people do with excellent results. However don’t try and keep the tomatoes too dry in an attempt to prevent disease problems. If you do you will almost certainly succumb to the cultural problem called Blossom End Rot. This shows up as a leathery dark to black spot underneath the fruit and is more likely to occur when the plants are grown within the confines of a Gro Bag. The black spot is probably a symptom of what happened three weeks ago rather than what occurred a few days ago as it takes time to develop within the fruit.

Nutrients and feeding

Tomato plants easily move most nutrients around the plants, particularly 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. If you are experiencing this problem now, continue to water and liquid feed you plant regularly but also add a level teaspoon of Calcium Nitrate to a gallon of water and add about a pint to each plant once every 10 days or so.
Feeding is also important now as both crops should be laden with fruit, however they do need a different NPK ratio of feed to each other. My favourite cucumber plant is a variety called Carmen which is very resistant to the powdery mildew that can so devastate the plants foliage and reduce it’s cropping potential. Cucumbers need to be fed with a high nitrogen feed to continue cropping as well as removing any taste of bitterness from the fruit. Continue to tie up the leading shoot and remove all the tendrils as the appear.

My favourite tomato, an F1 hybrid vine ripe variety called Cedrico also requires a level of Nitrogen in their feed for continued strong growth, but, for the remainder of the season, the ratio of Potash has to be at least twice that of the Nitrogen with a low ratio of Phosphates. Continue to remove side shoots and also keep your eye open for some extended growth that can sometimes shoot out from the tip of the truss, (picture attached) simply remove these with a pruner.


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1 thought on “Maximising your crop of Tomatoes and Cucumbers

  1. Hi, can you please tell wether I should plant cucumbers or tomatoes in the cooler part of my greenhouse? Thanks

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