Over the years I’ve been growing tomatoes, I have learned more and more about them and have a better understanding about how they behave so I thought I would write what I know about the three different growth habits of tomatoes and how to grow them.
There are three different types of tomato plants:
- Determinate;
- Indeterminate; and
- Semi-Determinate.
These words describe the way in which the plant wants to grow.
Other words and phrases are also used to describe the way in which we train the plants to grow:
- Cordon;
- Bush;
- Compact Cordon.
These descriptions are related as you will see from the more detailed descriptions.
Determinate
Determinate plants have lots of shoots and they flower at the end of the shoots. The shoots grow to approximately the same length, the flowers all come at about the same time and the fruit on a plant all ripen together over about two weeks or so. Because of the way they grow, the plant looks like a bush. Once the fruit have set, the plant diminishes in vigour and little new fruit will set. They tend to be smaller plants (up to four or five feet), sprawl about and shouldn’t be pruned (if you prune them it will reduce your crop). Depending upon the weight of fruit on the plant, they may or may not need support. Plants with standard sized fruit (e.g. Heinz H9129) will need some support to keep the fruit off the ground, plants with cherry sized fruit (e.g. Sweet Pea Currant) are much less likely to need support as the total weight of fruit will be less.
Determinate tomatoes are ideal if you want a lot of tomatoes all at the same time (e.g. for making batches of sauces) and if you are growing tomatoes on the patio where they are ideally suited to growing in pots. Commercial growers in places where the weather is suitable for outdoor growing tend to grow Determinate varieties so that they can harvest them mechanically all at the same time. For this reason, there are lots of different Determinate varieties available from the USA.
Indeterminate
Indeterminate plants have fruit over a longer season. They grow as a vine and fruit trusses appear along the length of the vine over the season ceasing only when the plant is killed by the weather. Sideshoots (new vines) grow out from the leaf joints along the main vine. These sideshoots themselves can have trusses of fruit and will generate more sideshoots, etc., etc.. Under the right circumstances vines can grow huge, sprawling and spread all over the place. The early set fruit will ripen, but the later setting fruit will probably not ripen on the plant before the plant dies in the cold.
When grown in commercial greenhouses, multiple sideshoots from a single plant can be trained through the greenhouse and, providing they are kept at the right temperature and with sufficient light and food can go on producing almost indefinitely.
When grown outdoors (particularly in the Southern USA) they tend to be grown in cages and the fruit is individually picked over a long period of time.
However, when grown in less clement places (such as in the UK) recognising that lots of fruit will not ripen before the plant dies of cold, we tend to grow them as a small number of vives in a Cordon, removing sideshoots as they appear to focus the plants energy into producing less fruit and clearing the leaves to allow the sun to ripen the fruit that has set. For this reason, the plants are usually “stopped” when they reach the top of the greenhouse to encourage the set fruit to ripen.
Most of the different sizes and colours of heritage and hybrid tomatoes are available as Indeterminate varieties. Examples of Indeterminate plants are Pink Brandywine, Red Berry and Ailsa Craig).
Indeterminate tomatoes are good in the greenhouse (where there is plenty of support) because they take up less floor space than determinate varieties. For this reason, commercial growers who grow under cover will generally grow Indeterminate varieties (many hydroponically) and heat and light their greenhouses to get a long season and large crop.
Semi-Determinate
These are actually better described as “Semi-Indeterminate” as they behave more like Indeterminate plants with fruit trusses being created along the length of the vine. However, like Determinate plants, the vine tends to stop growing when a small number of trusses have been set along a vine. As a result, the plants they typically grow to only three to five feet tall. They will need staking and some pruning to limit the number of stems. The best solution is to allow the sideshoots on the main stem to develop, but to remove any sideshoots on the subsequent vines. That way the total amount of fruit is increased but the set fruit has a good chance of ripening. Semi-Determinate are alright in the greenhouse (although you will need more space than for Indeterminate plants) but are less suitable for pots. An example of a semi-determinate plant is Gold Dust.
Choosing which varieties suit you best depends upon how much space you have and what varieties you are happiest with. We tend to grow Indeterminate and Semi-Determinate beefsteak, standard and cherry varieties in the greenhouse and Determinate cherry varieties in pots outside where we can move them around to catch the best of the weather to ripen them and provide snacks for the grandchildren.
Rules for Pruning and Harvesting
In summary:
- Determinate: Don’t Prune and allow the plant to create a bush. All the fruit will be ripe over a couple of weeks and should be harvested when ripe;
- Indeterminate: After deciding how many stems you want to grow (usually between one and three cordons) remove all subsequent sideshoots and stop the vines when five or six trusses have set on each cordon. Fruit will ripen over the season, should be picked when ripe and all fruit removed before the first frost kills the plant and unripe fruit stored and allowed to ripen or used green.
- Semi-Determinate: Allow all the sideshoots on the main vine to grow (secondary vines) but remove all sideshoots on the secondary vines. Each vine will set a small number of trusses (two or three) and , like Indeterminate cultivars, the fruit will ripen gradually over the season and will have to be removed before the first frost kills the plant.
If you go to (here) you’ll find a full list of all the tomatoes we describe and each description includes the growth habits of the individual tomato.