Answer: Your perennial plants, salvia, penstemon, lavender, rosemary and agapanthus should be deadheaded. Deadheading is the simple pruning of spent flower stalks and seed heads to clean up and rejuvenate the plant. Typically deadheading is done shortly after the plant stops producing new flowers. With some natives, such as Penstemon and Monkeyflowers, removing spent blossoms will encourage the plant to re-bloom again the same season. Your lantana can be sheared back at any time but flowering will be retarded for several weeks. I'd wait and prune it back (by as much as one third) in March so it will be ready to grow when the weather warms. Lavender should be pruned back now by about one-half. It will produce new foliage but won't flower again for a few months. Escallonia should be pruned in mid-summer or after it has finished flowering. You can shear it back into a formal shape or selectively prune it back by reducing the length of some of its stems. Grevillea can be pruned after it has finished flowering. You can prune it now. Again, shearing or selectively reducing some of the stems will encourage healthy new growth. Same for spirea and rosemary. Agapanthus should be deadheaded when flowering is finished and divided when it gets too large. You can safely remove the older outer leaves at the base but leave the new foliage in the center of the plant.
Best wishes with your garden!
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