Determinate or indeterminate?
Determinate generally grow to one "determined" size and have one large harvest.
Indeterminates get big and crazy and produce fruit over the course of the season.
I only sold one determinate variety this year…Roma. If you are growing a determinate, pruning is of little concern. You might consider removing a few lower branches to assist in air movement under the plant (reduce fungus concerns), but that is it.
Otherwise, read on for indeterminates…
1) Tools - Clean hands and tools. Please wash your hands before pruning. If you smoke, use lots of soap! Smokers can actually pass a virus from the tobacco in their cigarette to their lovely tomato plants. If you do smoke, you should quit….really…quit. If you use a tool (like pruning shears), you should wash these regularly to avoid passing disease between plants.
2) Timing - Ideally you would prune early in the day when the plants are dry and have plenty of day left to recover. That being said, I rarely do…I do have a day job! At the least, be sure the plants are dry. Pruning when wet will greatly increase chances of disease. Try to prune on days when you do not water (you should really do that in the morning too for the same reasons).
3) Training - You want the plant to grow to the correct size given the space you have given it. Tomatoes will grow very large and wild given the chance. So we need to control the larger growth pattern. You should already have something to assist it in growing upwards (cage, stake, twine, etc). Now, we need to control how it grows out of that space to maximize light/air exposure. The smaller the space dedicated to that plant, the smaller the number of main stems…and vice versa. However, I never give a plant more than four main stems…more than that and you will lose control. In my greenhouse, I only give each plant one! This allows each plant to concentrate on growing the largest possible fruit. Two is a good number given a smaller garden with space limitations. More stems may give you more flowers/fruit, but the tomatoes will be smaller. The less clusters, the larger the fruit! To add a new stem, you basically allow a sucker to grow. These should all grow from roughly the same area in a plant, above the first flower cluster if possible. If you are unsure of what a sucker is…keep reading.
4) Pruninga) The first area I prune is the lower portion of the plant. This promotes air flow under the leaves and on the soil…all very good for the plant and its health. You should remove any branches below the first set of flowers. To remove, just use your thumb and fore finger to snap off the branch at the main stem. If the branch is too large, you can use shears or scissors. Below is a good picture I found …
b) Next up are the suckers. I have yet to decide if these guys are good or evil. “Sucker” is not a very nice term in my opinion. These are basically the plants effort to spread out and take control. Each one is no different than the top of your plant…minus the fact they were not the first in line. Again, you may want to let a few of these grow to allow multiple “main” stems. Given the chance, a sucker will grow to monstrous size in a very short time. You may have a hard time differentiating between the main stem and many suckers. If you find this is the case, you may just need to cut one and allow the other to take over. You may want to allow one sucker to grow in addition to the main leader/tip on each stem at a given time (remove it when the sucker above grows to an inch or two). This is your backup if the main leader/tip becomes damaged. Here is a picture displaying a sucker. They basically grow between a branch and a stem (or in the crotch…sorry if that is mildly crude, but it is accurate). This picture displays both “Simple” and “Missouri“ pruning…stick with Simple. There is a reason they call it Simple :) . Remove suckers once a week...
As always, please let me know if there are any questions or experiences that may contribute.
Thanks and happy gardening!