My tomato plants have lots of yellow flowers but none have turrned into fruit. It is getting far too late now as they will never ripen even if they decide to fruit. My sweet 100 have fruit on which is starting to ripen. Anything I can do to make them fruit. I feed them with foliage food every week. they are in pots on a balcony as that gets the most sun.

Your flowers need pollenating. If you were growing in a garden planting plants thats attract bees is a big help.
The best thig you can do is hand pollenate. I use a small soft paint brush to 'paint' the flowers and move pollen around.

Heres a video with a couple of other simple methods
http://1greengeneration.elementsintime.com/?p=279

Thanks for that! I think the wind pollinated them but have done it by hand as well. I suspect lack of afternoon sun has something to do with it! I spied 2 tomatoes about the size of marbles this morning but autumn sets in early March in Wellington so a bit too late.

The weather/temperature can affects pollination as well. Tomato pollen is most mobile and viable on warm, dry days so the lack of sun may be affecting your pollination. Try the pollination thing on an hot, dry afternoon for best results.

I moved to palmy 6 months ago after living and gardening in Wellington for 10 years, I'd always have tomatoes ripening into March and even April so it might not be too late, depending on the light and heat the tomatoes get. At worst, you'll end up with green tomato pickle instead of ripe eating tomatoes.

A note for next season's crop, vibration of the plants helps pollination and fruit set, mine are in a greenhouse with a plastic cover which is susceptible to wind so doesn't get opened in windy weather, hence no bugs can get in for pollinating. I gently shook each plant each morning and have had great success with fruit set! Tomatoes are coming thick and fast now even with all the cruddy unseasonal we ather we've been experiencing in Taranaki.

3 tomatoes on each plant although sweet 100 are doing better. I think green chutney will be the answer!!