So, way back in the spring, we had talked about insulating our greenhouse with UV rated plastic. We’ve raved about the benefits, being one of the most impactful things we’ve done to our northern greenhouse. It enhances both shoulder season and also summer season performance, quite significantly.
One of our readers followed suit by insulating their greenhouse and immediately noted how different their tomatoes grew. They noted that the indeterminate tomatoes grew more “leggy,” almost like they weren’t getting enough sunlight. Though we addressed it in the comment, we figured this also presents a greater learning opportunity for everyone.
Tomatoes and their growth are very much impacted by the temperatures they receive. Outdoor grown tomatoes, in colder climates, will tend to grow much tighter and bushier than tomatoes that get a lot of heat. The cooler the air and soil, the more bushy they will grow. The inverse of this effect is that tomatoes will tend to get “leggier” in warmer climates, with much greater spacing between the internodes.
When you have an “OK” greenhouse with high degrees of temperature variability, you sort of get a blend of the two effects. But, when you can ensure your tomato plants get 80 degree temperatures through insulative benefits, almost all of the time, it’s like they were transported to their perfect growing climate.
Generally speaking, that greater internodal spacing (from warm grown environments) are “more” ideal. You get better spacing between fruit and better airflow through the plant. But, most importantly, those higher temperatures are responsible for more rapidly maturing the desired fruit.
Our images demonstrate the different effects of growing temperatures on tomatoes. We have a purely outdoor, subarctic soil grown tomato that’s quite small and bushy, about 3 foot tall. Then, we have our hydroponic setup that promotes warm temperatures, but still gets the brunt of large temperature swings. These are about 4-5 foot tall. Then, we have our insulated greenhouse tomatoes that are very tall with much better spacing between each node and are reaching 7+ foot tall.
Not many plants radically change their growing behavior based on temperatures, but tomatoes are definitely one of them. We can also appreciate the “shock” that might come from altering the environment, we went through a similar process when we insulated our greenhouse. It’d be similar to growing in the south one year and the north the next, a radical change!
Lastly, as a bonus tip, you can also see one of our alternative growing methods for growing tomatoes in ground. Here, we just let the indeterminate tomato “do what it wants” and provide very little management. We can do this since the cooler temperatures will keep the plant “in check” and we also have the space where we can afford a bushy, sprawling tomato plant.
Some people have the perception that determinates or indeterminates are what makes tomatoes “bushy,” but it’s also influenced by the growing method and temperatures that the plant receives!
