Recently I received an email questioning how to care for Sea Foam sage (Artemisia versicolor), Silverheels horehound (Marrubium rotundifolium) and partridge feather (Tanacetum densum ssp. amani). Great question, because these three plants all have fuzzy, silver leaves and do require slightly different care than many other groundcovers.
Silverheels horehound tends to mound up on itself over the years, but the only real trimming it needs is to remove any withered or dead stems in late spring. Once the flower stalks start shooting up, the plant’s energy is devoted to reproduction. Since the flowers are relatively insignificant aesthetically, I tend to cut those stalks all the way back to the crown as they emerge to keep the energy flowing to the foliage instead. On the other hand, several species of moths seem to prefer these flowers, so it might be a good idea to leave a plant or two to flower (for the moths) and then remove those stems when the flowers are done.
Partridge feather is much easier to maintain – again, the flowers tend to rob energy from the foliage, and I don’t really care for them much personally, so
I also remove these flower stalks as they appear, and the lovely feather foliage stays nice and dense.
Sea foam sage is the easiest of all three, as it looks quite nice in or out of flower. The only care this plant needs is to be cut back nearly to the ground in early spring. I usually wait until I see new little buds emerging, then cut back to as low as possible but making sure I see new growth below the cut. Trim these evenly so they’ll push out in a more rounded mound.
All three of these plants will not tolerate humid conditions, nor very wet leaves. Avoid northern exposures because of lingering winter snow loads. Otherwise, they’re basically pest and disease-free, deer- and rabbit-resistant, and love hot, dry gardens and landscapes. Could hardly be easier!
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