Zvi Howard Wener / Chief Agrinomist / Zviw@zeraim.co.il

Question: What are the differences between indeterminate and determinate tomato plant types? What are semi-determinate tomato plants?

Answer:

1. Determinate or “bush” tomatoes are said to have a determinate growth pattern because they are relatively compact, grow to a certain height and set all their fruit in a relatively short period. This is especially useful where the growing season is cool or short, or both. Fruit ripening is concentrated within a relatively short period and this type of plant is suitable for mechanical harvesting as with processing tomatoes.

The first flower truss and new growth point develop normally but there is a tendency for lateral axes to terminate in one, and more often, two consecutive inflorescences without developing a new growth point. As a result of this natural termination, the lower side shoots induce the bushy tendency. The main stem terminates in the same way.
Semi-determinate tomatoes are determinate varieties that are strong enough to be trellised on sticks, wires and strings and grown upwards, often up to 2 m, until they stop on their own. The trellising method directs the plant’s bushiness upwards. Morphologically they are determinate tomato plants.
The number of leaves below the first flower cluster (inflorescence) on the main stem is 6-14; between the first and second inflorescence 2-3 leaves; between the third inflorescence and all additional ones there can be 0-1-2 leaves.

1. Indeterminate tomato plants grow over a long period, often up to 11 months, in greenhouses and often reaching lengths of 10 m and more. They are usually grown as a single stem with side shoots (lateral branches) always removed and they continuously and regularly produce flowers and fruit. Indeterminate varieties can be grown in open fields with trellising or in greenhouses twisted around strings tied to a crop wire and are stopped either by the weather or by the grower himself.

The number of leaves below the first inflorescences on the main stem is 6-14; between the first and second inflorescences 3-5 leaves and after the third flower cluster there are always 3 leaves.