Determinate and indeterminate tomato plants – what’s the difference, and why you should care
There might only be two letters difference between them but knowing the distinct features of each classification can have a big influence on which type of tomato plant you choose to grow, as well as how to support and prune them.
Let me break things down for clarity to ensure you have the best tomato variety for your space, and to help you confidently prune them.
Determinate tomatoes
A great option if you’re growing tomatoes in planters, or if your garden has a shorter growing season.
Determinate varieties are also bush-type tomato plants, as they grow more like a bush than a vine.
Determinate tomatoes grow about 3’ tall and need little to no pruning.
These tomatoes are genuinely a patio gardener’s dream, as they can be supported with simple cages and are an excellent choice for containers or large pots.
Determinate tomatoes set fruit, then concentrate on ripening all that fruit in one big wave. This makes these tomatoes great for cold-climate gardeners who need to harvest their entire crop within a couple of weeks.
Indeterminate tomatoes
Perfect for tomato growers with plenty of space, prefer to pick your tomatoes over several months, and are prepared to provide sturdy support for your tomato plants.
Indeterminate varieties are also known as vining tomatoes.
They usually grow to about 6’ tall, and don’t be shocked if they hit 10 feet! These plants are huge!
Indeterminate tomatoes aren’t ideal for planters, although it is possible to achieve success with a very large and deep planter.
Indeterminate plants keep growing taller and taller, setting, and ripening fruit as they grow, until the frost kills them completely.
These indeterminate varieties require more space, support, attention and general commitment from gardeners than their determinate counterparts.
Why it’s important to Prune Tomato Plants
It keeps your tomato plants compact to help you maximize your garden density
Makes it easy to use supportive stands like ladders, weaves, or other poles
Maximizes tomato production by helping the young tomato plants focus on fruit development. If you live in regions with short growing seasons you may benefit from starting your pruning of suckers in late summer for this reason.
Minimizes disease problems by improving air circulation
When pruning, for best results, moderation is essential. Too much pruning can remove leaves that your plant needs to stay fed. Reducing too much of your plants foliage can expose the fruit to full sunlight, which could result in the equivalent of a painful sunburn, and you don’t want that. 😊
How to Pruning determinate tomato plants:
So, you think that it’s time to prune your determinate tomato plant? I can help with that!
Although vining tomato plants generally need more tending, determinate tomato plants still need a little pruning to thrive.
Pruning helps to keep your tomato plant’s structure strong, and by removing any limbs that aren’t required, your plant will be able to concentrate its energy on fruit development.
Pruning a determinate tomato plant is an easy job, but it is also an important one. If ignored entirely, you’ll end up with a plant with lots of foliage in places where it could have grown more fruit, and after all, I want as much fruit as I can get!
For best results prune your determinate tomato plant by removing all the suckers you can find between ground level and the first flower cluster.
Suckers are small stems that grow between your tomato plant's main trunk and stem(s). They usually grow at a 45-degree angle, which makes them easy to spot.
Pruning indeterminate tomato plants: A simple how-to
These plants usually grow to about six feet tall and keep growing, setting, and ripening fruit as they do so.
Pruning your indeterminate tomato plants helps to keep them strong and structured, and removing any heavy, unwanted limbs, will ensure that your plant needs less external support.
To begin the process of pruning indeterminate tomato plant, I recommend:
using pruning shears to snip off all the blossom clusters that appear before the plant is around 16 inches (40 cm) tall
allowing the next cluster of blossoms to develop after your plant reaches 16 inches (40 cm) in height
snipping off all lateral branches below the developing cluster of new blossoms with a sharp knife.
Suckers
(Reminder: Suckers are small stems that grow between your tomato plant's main trunk and stem(s). They usually grow at a 45-degree angle, which makes them easy to spot.)
After your initial pruning stages are complete, cut off your plant’s suckers that are just above the second leaf from the bottom.
For best results, make sure to leave a couple of leaves on each stem to help keep your fruit shaded while allowing for maximal photosynthesis.
If left alone, suckers can grow into main stems that produce leaves and fruit.
To keep your growing process going for months to come, I recommend leaving between three and five suckers on your plant, untouched, and allowing these to grow into main stems.
Final tips for pruning tomato plants
Remove any broken, diseased, or damaged stems as soon as you notice them. If you leave damaged areas on your plant, disease can enter and spread rapidly, so avoid this at all costs.
We recommend pruning your vining tomato plants one final time about a month before you expect the first fall frost.
How to Prune Tomato Plants of any variety
This applies to both tomato plant varieties if you use cages or towers to support tomato plants. With support tools like these, pinch suckers from the lower stems, allowing the ones higher up to grow.
Look for that group or cluster of smaller stems where flowers and fruit develop, this is called a truss.
The general rule of thumb is that leaves can removed gradually up to the first truss on a young plant that hasn't started producing tomatoes yet. Then, after the maturing plant starts producing ripe tomatoes, you can then start slowly removing a few that are above the first truss.
Keep in mind that de-leafing a plant too quickly and removing too many leaves can result in a poorer harvest, so slow and respectful is key.