Answer: Yours are a little tall for pinching Pinching should begin early. You can start the process when the zinnia seedlings have developed their second or third set of true leaves. Remember, at each node (where the leaf stem or petiole meets the main stem), there is a bud. When you pinch off the growing point, you are removing hormones which suppress the growth of those lateral buds. Once the lateral buds start to grow and they produce a second set of leaves you can pinch those to encourage even more side growth. Since your plants are tall already you might just pinch the very tip out to encourage branching or you might just want to set a bamboo skewer next to the stem of each plant as you set it outdoors to help steady it until it becomes strong enough to stand on its own. In the meantime you can lightly brush the tops of the plants several times a day to get them used to the breezes they will experience outdoors. Best wishes with your zinnias.
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