Certified GKH Gardening Expert
This is a practice called pinching. Whether you do it or not depends on the type of growth you want from the plant. Pinching will encourage stemmed plants to branch out and grow more fully. Here is more information: https://www.gardeningknowhow.com/garden-how-to/info/pinching-plant.htm What type of seedlings do you have? We can let you know if you want to pinch them or not.