I think I've finally got a handle on tomatoes. Been pulling in an armload of Romas and a bowl of the cherries every evening (the picture is of today's cherry tomato harvest and a few days' of Romas). Starting from seed is still hit or miss, so this time around I bought healthy looking plants from the local garden center.
Here are the things that, anecdotally, seem to help:
DAILY water
Lots of compost
Plenty of well drained soil (I have a 1 ft high raised bed that was loosened up 1 foot deep underneath when I installed it)
Grow during winter months
Calcium supplementation, either added to soil or as a foliar spray
Occasional addition of coffee grounds to soil
This seems to be working for me, anyway. I think compost and a steady water supply are probably the most important factors. Incidentally, I used no other fertilizers aside from the amendments mentioned above.
Your feedback is appreciated! It seems like would-be gardeners are often frustrated by growing tomatoes in Hawaii. In the future I will try to post a more comprehensive and evidence-based guide. Good luck!
