Thank you for taking the time to read my message.
I have a few questions regarding a variety of indeterminate tomatoes I have growing in my raised bed:
Some basic information:
– Full sun
– Approximately 1.5 square feet per plant
– About 18 – 24 inches tall at the moment
– Rich substrate with black earth, perlite, peat and fertilizer (blood, bonemeal, potash)
– Supported using cages made from poultry wire and staked down using u-spikes
1. How far in advance of the frost date do you recommend “topping” indeterminate tomato plants? Or at what height?
I have found conflicting information regarding pruning.
Pruning foliage near ground level is universally recommended to avoid pathogen exposure and increase airflow. Aside from that:
2a. Given the robust support system, can I allow the suckers to grow into multiple mains to increase my yield, even if the fruit is smaller? Does our climate preclude multi-stem plants?
2b. Is it direct sun irradiation or the sugars from photosynthesis that ripen the fruit? To that end, is denser healthy foliage better with multiple main stems, or sparser foliage for more direct sun exposure?
Thank you in advance,
Before I answer your direct questions, I’m going to clarify what a “determinate” and “indeterminate” tomato plant is.
Determinate plants are basically bush type plants (rarely reaching more than 4-5 feet tall), they generally do not require staking for support, they set all their fruit at once over a short period of time and then plant vigor declines fairly quickly. These plants are ideal for producing large quantities of fruit to be made into sauces.
Indeterminate plants are vines which can grow to be quite large, they require staking/caging and produce a slow but steady supply of fruit until the first frost.
Now to your questions:
- “Topping” is usually done 2-3 weeks in advance of the expected first frost. This stops the plant from actively growing and makes it put its energy into maturing and ripening any fruit still on the vine. This practice can also be done earlier if a vine is growing vegetatively well beyond its support system and not producing fruit – this will force the plant to grow bushier and flower.
- Pruning out suckers is indeed a practice you can do, but be aware that the plant needs leaves in order to grow and produce fruit so there’s a balance. I usually suggest taking out about 1/3 of the suckers as the plant grows. If you have taken the leaves & stems from the bottom 12 inches of the plant in order to try to minimize water splash and disease transfer, then if you don’t take out some of the suckers above that, you’ll end up with a very top heavy unstable plant. This practice will also increase air flow throughout the entire the plant.
- Once individual tomatoes reach their mature size on the vine, they begin to produce ethylene gas, this hastens the ripening process and the colour will begin to change. This usually happens when daytime temperatures are between 10-30 degrees C.
I hope this information is helpful.