Answer: You can deadhead penstemon by cutting the flowering stems down after the flowers fade. In the autumn you can cut the foliage down to the ground and new stems and leaves will emerge the following spring. Yarrow (Achillea) can be staked if the flower stems begin to flop over. You can cut the flowering stems when they're fully opened and hang them upside down to dry if you'd like to use them for dried flower arrangements. Otherwise, trim the spent flowers down to keep the plant looking neat. In the autumn you can cut the foliage down to ground level.
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