We must consider whether to shade tomato plants in the greenhouse.
Think about temporary shading first, because if you spray on shading the sun will never return and in the autumn you’ll have to clean it all off.
The easiest form of shading is newspaper clipped to the canes or strings.
This can be done on mornings when it’s going to be hot and taken off again when it’s dull.
If we keep the temperature moderate all summer, the fruit will set properly.
Shading, particularly when flowers are appearing, helps prevent the pollen from overheating. If it gets too hot the pollen grains, which are live cells, die and the flowers fall off leaving fruit no larger than a pea.
Whichever planting method you have decided to use, try to water the plants in the late evening from now. Plants absorb water far better during the night.
Once the first truss of fruit is the size of a pea, add a quarter-strength liquid plant food to the water at every watering. This ensures even growth and good quality fruit which will be tastier if you use a food especially formulated for tomatoes.
Regular feeding will also ensure fruits aren’t too acid and they will have more flesh rather than a lot of seeds and hardly any flesh.
Keep the windows and door open when it’s going to be hot. Cats and birds can be kept out with wire mesh in the doorway and don’t worry about a light breeze, it will help pollination. However, the plants won’t like a cold draught as rapidly-changing temperatures cause poor pollination.
If you get the chance at lunchtime, give the strings or canes supporting the plants a sharp tap a couple of times and you will see pollen falling on to blooms lower down the stems.
If the fruits become brown around the scar where the flower was borne, this is because of poor watering. Overcome it by water in the evenings rather than when you feel like it! Add a small amount of calcium nitrate.
A little later in the summer, the leaves will start to show signs of deterioration. Watch for brown patches which occur suddenly overnight. This is tomato blight but is easy to remedy by spraying during the evening with copper fungicide.
Whitefly is the worst pest of all on tomatoes but they can be controlled.
Yellow sticky cards placed at the tips of the growing plants and moved up every week help reduce the population. If they don’t seem to work, give the plants a regular shake, remembering that one whitefly trapped on the sticky surface means you have prevented several hundred being born.
It is far better to leave leaves on the main stems all the time they are green, They are there to produce energy to swell the fruits. It’s not a good idea to remove them. If you think this helps ripen the fruit, you’re wrong. Warmth and potash will do that.
My final tip is to alter feeding as soon as the weather gets hot. Change the feed to one for vegetables as it’s lower in potash. If we continue to feed with high potash feed the tomatoes will be hard on one side or have unripened lumps in the middle. So listen to the forecast to get it right.
THIS WEEK’S TOP TIP
Lots of pruning planned? This is a busy time because spring-flowering shrubs and hedges need to be cut back. If you are one of those who takes green waste to a recycling centre you will be able to get more in the car if all the material is cut up so it can be put into large plastic sacks. It’s far quicker to dump at the other end.