Tomatoes: Determinate vs. Indeterminate?

Indeterminate and Determinate: Five to 10 leaf fronds emerge out of the primary shoot of a young tomato vine before a flower cluster emerges. That means there will be at least 4 internodes and up to 9 internodes (stem segments between leaf axils) before a flower cluster appears on the vine.

Indeterminate: Although indeterminate plants appear to have a single main stem, this is actually not the case. The growth of the primary shoot ("main stem") ends with the formation of the first flower. Upward growth continues because the last leaf initiated before the flower cluster (which actually grows to occupy a position above the cluster) produces a side shoot. This side shoot produces three more leaves before it terminates in a flower cluster. This process of initiating new growth from a side shoot of the last leaf initiated before the flower cluster continues indefinitely, giving the appearance of a mainstem with a flower cluster in the internode between every three leaf nodes. Examples: Big Boy, Better Boy, Brandywine, Big Beef, Sun Gold, many heritage types.

Determinate: In determinate cultivars the process differs in that the side shoot above the first flower cluster produces 0 to 2 leaf nodes and a flower cluster but no further vegetative shoots. This ends the upward growth of the plant, making the apparent main stem much shorter. Many side shoots arise from the primary shoot, giving the plant a bushy appearance, but each eventually terminates in a flower cluster as did the primary shoot. The simultaneous growth of many flower clusters on determinate vines promotes earliness and concentrates fruit maturity compared to indeterminates. Examples: Mountain Spring, Scarlet Red, Mozark, most modern commercial canners.

"Semi-determintes:" Shoots of semi-determinate plants produce several flower clusters to the side of an apparent main stem, like indeterminates, but eventually the shoot terminates in a flower cluster, as in determinate plants. Example: Celebrity (and for me, the Bradley tomato I've grown for several years now).

Determinate tomatoes produce fruit at the ends of their branches. They stop growing while they are fairly short. Indeterminate types, in contrast, produce fruit at intervals along their stems.