Silver Edged Horehound (Marrubium rotundifolium)

Horehound (Marrubium rotundifolium) ‘Silver Edged,’ also known as Silverheels Horehound, is a low-growing, drought-tolerant groundcover that I highly recommend for difficult, dry spots in the garden. It thrives in hot, dry conditions and poor soil, and its soft, silvery foliage has an almost felt-like texture.

In our garden, plants that prefer dry conditions are actually a challenge. I’ve killed numerous agaves and other xeric-type plants. I’m sure it’s because we water regularly, and I always amend the soil with compost and manure.

However, the planting strip along the roadside doesn’t get as much water as other parts of the garden. I would guess that it is also the hottest area of the garden. Even though it is north-facing, the area gets quite a bit of sun, especially during the height of summer. I’ve tried to plant mostly species along this stretch that appreciate these conditions, although I’m not always successful, and inappropriate plants keep sneaking in.

When I do water this bed—the “hellstrip”—I try to position the sprinkler so that it avoids hitting the horehound. This plant not only dislikes excessive water, but it also doesn’t appreciate overhead watering. Of course, during the winter months, there isn’t much you can do about that. Horehound is well suited to a Mediterranean type environment, with dry summers and wet winters. The key is good drainage. In addition to adding crushed gravel to the planting hole, I also mulch around the plant with pea gravel or grit.

Horehound has long been associated with healing powers, whether for a sore throat or even the bite of a mad dog. However, that reputation belongs to Marrubium vulgare, commonly known as White Horehound, rather than Marrubium rotundifolium. To my understanding, Marrubium rotundifolium does not have the same established medicinal qualities.

This is the plant’s second year in our garden, and I would not call it a fast grower. It forms a nice cushion, reaching only about an inch or two in height and spreading 8–10 inches. For a hot, dry spot where many plants struggle, however, its slow growth is hardly a drawback. Its silvery foliage and low, compact habit make it an especially attractive choice for a gravel garden, rock garden, or other well-drained location.

Text and photos by Phillip Oliver, Dirt Therapy