It can be genetic. There are varieties that have the precocious flowering trait that will always set flowers by the 6th of 7th leaf stage. It can be physiological. If the plants are kept root bound but have plenty of nutrients, it will induce early flowering. It is NOT caused by cold weather. In fact, cold temperatures slow down seedling growth so much that they won't set flowers until the cold shock has been offset by much warmer weather. Cold temperatures within some limits are beneficial to tomatoes. You can search and find studies where tomatoes exposed to cold temps for about 2 weeks produce more flowers and set more fruit. Regardless of why the plants are flowering, I would pull off any flowers or fruit until the plants have been in the ground at least 3 weeks. Plants that try to support fruit load any earlier don't have a root system developed enough to continue growing at the same time. As a side note, the most beneficial thing you can do to a tomato seedling is to semi-starve it for water. The plant will develop a much larger root system. This pattern of growing more roots will continue even after the plant is transplanted into the garden. These plants will produce a larger crop because the root system is larger. Darjones

mulio- I'm interested on your suggestion to loose the mulch? Whats your opinion on that? cca714- I agree with mulio on leaving the flowers be. They are probably a ways away from setting fruit and by that time that plant could be twice as tall. Good to hear another person like yourself is growing heirloom tomatoes for the first time. Good luck! Damon

Have you ever grown tomatoes? It's completely normal.

Interesting and challenging setup. Since you mention awful soil, and perhaps cost consciousness, you can always fill the garden plot with leaves at the end of the growing season. Grinding them up is preferable but not necessary. I mention leaves because they are free, often plentiful, and they do so much good for the soil. You can plow them under a month or two before the growing season, if you feel like it. The type of leaf to avoid is walnut because walnut trees contain a plant growth inhibitor. If you live within driving distance of the ocean, try to fill a few bags with seaweed. It has just a little NPK, so it would be hard to overfertilize your plants with it, but it has lots of minerals that the soil needs. Just be sure to wash the salt off very very well (both wash and soak?). Afterwards you can apply it fresh, dried, aged. Wishing you luck with your grow!! Here is a link that might be useful: Leaf and soil food web discussion