"Janice" wrote in message
...
I've grown some tomato plants in growbags in a greenhouse. Got lots of
tomatoes (although they're still green).

But the stem at the base of each plant is very thin and weak (the stems
are
thick at the top). Fortunately, I supported the plants on strings so
they're okay, but without the supports there's no way the stems would be
able to hold the plant.

What did I do wrong and how do I avoid weak, thin stems in future?

You probably grew the seedlings on in too much heat and/or too little light.
This makes them tall and 'leggy'.
Plants grown in strong light and lower temperatures tend to be more stocky.

This problem can arise with outdoor tomatoes if they are started indoors too
early, and then are kept waiting because it is too cold to put them outside.

Basically anything that makes the seedlings tall and thin can cause this.

HTH
Dave R