Answer: I'd wait until signs of new growth appear on perennials before sidedressing. On seedlings, I'd wait until the true leaves appear (the next set after the seedling leaves) before fertilizing. Remember to fertilize with a complete mixture, perferably organic, early in the season to promote growth of roots and shoots. Don't over fertilize plants, especially flowers and vegetables with nitrogen, since you may get all leaves and few flowers and fruits.
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