Answer: Tomato plants fall into one of two types that affect ultimate plant height and cultural requirements. Tomatoes are determinate if they eventually form a flower cluster at the terminal growing point, causing the plant to stop growing in height. Plants that never set terminal flower clusters, but only lateral ones and continue indefinitely to grow taller are called indeterminate. Older varieties are almost all indeterminate. These can be counted upon to produce abundant foliage and to ripen flavorful fruit. Newer varieties seem to be more compact (determinate) and they tend to ripen fruit earlier in the season.
Grape and cherry tomatoes are considered compact and can be planted 12" apart.
Your full sized tomato plants should be planted 18-24" apart to provide adequate growing space as all are indeterminate varieties.
Hope this information provides some guidance on spacing your tomato plants.
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