An easy way to get sturdier seedlings is to pinch them off as they are growing. In the photo above, you can see the little side shoots coming out from where I pinched off the central leader of my ageratum plant last week. Because our weather is so fickle this spring, I pinched off many more of my seedlings than I usually do. I fear they could be growing under the lights for quite awhile yet, and I don’t want them to get too tall and leggy.
You can use your fingers to do the pinching, but I get better control using a pair of sharp-pointed scissors. Always pinch above the second set of leaves (remember, the first set are cotyledons, not true leaves).
There are some annuals that you shouldn’t pinch including zinnias. Zinnias will still grow side shoots but they come out rather lopsided and can make the plants look unattractive. Over the years I’ve read more than once that if you pinch off the central leader of a celosia plant that it won’t bloom. I searched online and haven’t found any information to substantiate that claim, but I’m not taking any chances.
Some plants that respond very well to pinching include ageratums, salvias, coleus, impatiens, marigolds and tomatoes. Besides pinching off plant growth, you should always remove any flower buds that form while the plants are still growing under lights. You want them to put their energy into stronger roots, leaves and stems instead.
It can be intimidating to lop off healthy growth from something you’ve babied from seed, but you’ll be rewarded with stronger, bushier plants that can better withstand the rigors of Mother Nature.