Pinching

You count the 'true' leaves ignoring the two 'cotyledons' (which are the first leaves to emerge from the seed and are a different shape)



When there are 4 'true' leafs nip out the growing point. This encourages new shoots to develop and creates a bushier plant.

 

The 'growing point' is just that, the very tip on the central stalk.

 

It applies to a wide range of plants, but particularly those that you want to be that wee bit bushier rather than a single stalk with a flower at the top.

 

As FC said, the best example is sweet peas, I think it's essential to do for them

 

@Eldy hopefully this will help:



At the moment (June) we are pinching/nipping out side-shoots on tomatoes. This is done on so called 'cordon' or 'indeterminate' varieties ('bush' varieties you just leave alone).

For indoor tomatoes I allow about 8 trusses to form then pinch out the growing tip, this 'stops' the plant so it puts all it's energy into producing fruit. 'Stopping' will take place in August time. For outdoor tomatoes you need to 'stop' them when there are between 4 to 6 trusses. The idea being your trusses will all ripen before the season ends i.e. frost/cold takes its toll on the plants.

 

Yes that's showing just one truss - but a truss is flowers not leafs. That drawing above is not so clear so I've found this picture which is a bit better below.

A truss has flowers (or buds) on it, there should be no or very few leafs on a truss, they look like this:



So very different to the 'side-shoot' which emerges from the joint of a leaf and the main stem.

Don't remove the trusses - the flowers turn into the fruit. When the flowers finish you should see little fruit starting to form. If no fruit forming then do as follows:

Sometimes the flowers don't 'set' in a greenhouse due to lack of insects/wind movement. Instead give your tomato plants a gentle tap each time you go into the greenhouse, this shakes the flowers and causes pollen to transfer from the male to female part - i.e. you are fertilizing the flowers.