It’s time to consider whether to shade tomato plants in the greenhouse.
Think about temporary shading. If you use spray-on varieties the sun will never return and in the autumn you’ll have to clean it off.
Large sheets of newspaper clipped to the canes or strings with a peg are easiest. Do this in the mornings when it’s going to be hot and take them off again when the weather is dull. If we keep the temperature moderate all summer the fruits will set properly.
Shading, especially when flowers are appearing, helps stop pollen overheating. If it becomes too hot the pollen grains, which are live cells, die and the flowers fall off leaving pea-sized fruits.
Whichever method of planting you use, water the plants in the late evening from now. Plants absorb water far better at night. Once the first truss of fruits are pea-sized, add a quarter-strength liquid plant food each time you water. This ensures even growth and quality fruit which will be tastier if you use a special tomato food. Regular feeding also ensures the fruits have more flesh rather than lots of seeds and little flesh.
Keep the windows and door open when it’s hot. Keep out cats and birds by using wire mesh in the doorway and don’t be too worried about a light breeze, it will help pollination. However, tomatoes don’t like cold draughts as rapidly-changing temperatures cause poor pollination.
If you get the chance at lunchtime, give the plants’ supports a sharp tap a couple of times and you will see pollen falling off on to the blooms lower down the stems.
If the fruits get brown around the scar where the flower was, this is because of poor watering. Overcome this by watering during the evenings. Add a small amount of calcium nitrate.
Later in the summer the leaves will deteriorate. 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 are the worst pest, but you can control them. Yellow sticky cards put at the plants’ tips and moved up each week, help reduce the population. If they don’t seem to work, shake the plants regularly remembering that even one whitefly given a sticky end means you have stopped several hundred being born.
It is far better to leave the leaves on the main stems while they are green. Their purpose is to produce energy to swell the fruits. They do not help ripen fruit, it’s warmth and potash which do that.
Finally, alter the feeding during hot spells. Change the feed to one for vegetables which is lower in potash. If you continue with a high potash feed your tomatoes will be hard on one side or have unripened lumps in the middle.
TIP OF THE WEEK
Do you have lots of pruning planned? This is a busy time because the spring-flowering shrubs and hedges must be cut back.
If you are a gardener who takes green waste to a recycling centre you will be able to get more into the car if the material is cut up and put in large plastic sacks.