Indeterminate tomato crops need regular pruning only because they develop until the first frost. Determinate forms have a shortened growing season along with a well-defined amount of flowers, leaves and stalks, so they do not need pruning. For indeterminate tomatoes, then you must decide if you would like one growing leader or more. Leaders, commonly called main stems, are the large stems that sprout branches, suckers and leaves. Single-stem plants do not need much space, but they create fewer vegetables than multi-stemmed plants. Pruning will limit the amount of bad-quality tomatoes and encourage the increase of high-quality fruit.
Pinch off any suckers growing from the crotch of every division following transplanting the seedling. Grip suckers between the thumb and forefinger to pinch off small growths or use pruning shears for large ones. Also pinch off any metallic flower buds.
Keep on pinching off suckers growing in the crotches weekly and blossom buds that appear two to three weeks after transplanting.
Allow the first pair of blooms to form when the plant is 12 to 18 inches tall. Pinch off any leaves and suckers beneath the blossom cluster. Allow a take to grow from the leaf axil, the angle between the stem and leaf, over the blossom cluster to develop two leaders. Permit a take develop from the leaf axil over the second leader to develop three leaders.
Pinch out suckers routinely to encourage stronger growth and plant health. Remove suckers in the crotch when they’re small, between 2 and 4 inches.
Locate the growing stage, which is that the very top of this leader. Trim off the growing point once it develops seven or six trusses (the blossom clusters that develop fruit). Pinch off any trusses that develop afterward.
Prune off any yellowing, dying or diseased leaves. Pinch off any new flower buds in mid-August to avoid fruit from setting late in the fall.