This week on the TC3 Farm: Hardening Off and Potting On by Hannah W.
Now that the days have been getting warmer, if you walk up to the greenhouse on the TC3 farm, you’ll see a full table of seedlings outside, getting used to the wind and cooler temperatures. After a while, they’ll be brought back inside for the night. This process of “hardening off” helps tiny seedlings prepare for life in the farm field. As they grow, trays of seedlings are gradually moved farther from the greenhouse heater, then eventually placed on the ground, where it’s cooler still.
The final steps in hardening off involve moving the seedlings outside. Even though the plastic on the greenhouse seems thin, it does offer a bit of protection from the sun, so plants also have to get used to the brighter sunlight as they transition outdoors. Seedlings may be brought outside for just a couple hours at first, then graduate to spending the whole day outdoors.
This week, the laboratory portion of class featured a tomato potting-on extravaganza. “Potting on,” refers to transferring a plant into a larger container with more soil. As the seedling grows, its roots spread out through the soil in the container, absorbing nutrients. After a while, the seedling will eventually run out of nutrients in the small area of soil it has to work with.
Tomato seedlings also compete for light, which is another reason to pot them on. Tomatoes, as warm-weather crops, spend a long time in the greenhouse and need space to spread out their leaves. For plants like bok choi, which are cold-hardy and can be planted out in the field soon, there’s no need to move them to larger pots.