Most of my tall varieties have now reached the polytunnel roof, so it’s time to begin removing the growing tips.
The last couple of weeks I’ve mention about pruning and how it can be used to encourage plants from the vegetative to the reproductive phase where emphasis is on growing tomatoes rather than growing leaves.
Another way to encourage plants into the fruiting mode is by the amount of food we give them, also known as increasing the nutrient strength.
Steering by feeding
Plants that are given a weaker feed tend to be more vegetative than those given a stronger feed. In other words, feeding plants a slightly stronger strength of food will encourage the reproductive phase and fruiting. Feeding tomato plants a slightly weaker strength of food will tend to keep them in their vegetative mode and delay fruiting.
Now you may say … what was all that stuff about not feeding plants too much …. and, it’s better to feed little and often – wouldn’t that also keep them in their vegetative mode?
The answer is that the two tips above work well as a general rule, but as our plants approach the desired amount of trusses, it is all about encouraging them to put their energy into growing tomatoes. The method I’m about to describe is a temporary boost.
How much extra should I give and for how long?
After your container grown plants have been in their present soil for about six weeks and the nutrients in their soil have been almost entirely used up, the plants will depend on us for almost all their nutrients. At this point the recommended dose for feeding plants growing in soil can be doubled!
I am talking about plants that have reached a good size and have the amount of flowering/fruiting trusses you are happy with – usually four to seven trusses for a tall variety.
The advantages of increasing the nutrient strength
- Steers plants away from leaf growth
- Increased fruit growth
- Sweeter tasting fruit if done when the tomatoes are swelling
The disadvantages if too much food is given
- Wilting in hot weather
- Increased risk of blossom end rot
- Slightly smaller size fruit
Most Tomorite type feeds are reduced to half strength to allow for the nutrients in the soil. However, when the nutrients in the soil have been more or less used up by a plant in a container or grow bag, the given food can be increased – by up to double the standard diluted rate.
For how long?
Every July I give my soil grown plants a three week boost of tomato food. This can be done in two ways…
- Feed the same amount twice as often
- Double the strength and feed at the same intervals
The first option is less stressful for your plants, especially in hot weather, because adding more mineral salts to their water supply reduces the speed at which they can absorb water (see osmosis).
Flushing the soil
After the boost period of three weeks, plants should be given a good flush with plain water to remove any build up of mineral salts, then resume standard feeding.
Warning – Disclaimer
Do this with care … it’s best to try it on just a few of your plants and compare the results to those fed with only a standard amount of feed. I think you will find that the tomatoes given the higher strength/frequency feed will taste better and the plants will be more productive. Remember to stop after around three weeks!
The King Flower
The first flower on each truss (the flower nearest the main stem) is sometimes known as the king flower.
It is usually the first one to set, and because of this, has the greatest demand on the plant. It’s a bit like a nest full of birds – the one that shouts the loudest gets the most food and is the biggest!
Demand and supply
Not all tomatoes on a truss are equal – the ones nearest the stem are usually the sweetest because they are nearest the food supply.
Because of the dominance of the king flower and its tomato, many growers remove the first flower on each truss before it sets. This has the advantage of allowing the rest of the tomatoes to grow to a more consistent size and shares the plants resources more evenly between the rest of the tomatoes.
I’m not suggesting we start removing the king flowers, but it is one reason why tomatoes on a truss can grow to inconsistent sizes.
The weeks are flying by!