Plant taxonomy classifies rock cotoneaster as Cotoneaster horizontalis. The genus name thus doubles as part of the main common name. Other common names are "wall" and "rockspray" cotoneaster. These common names allude to the widespread use of C. horizontalis as a rock-garden plant and as a plant grown either up against a wall or hanging down over the side of a wall. It belongs to the rose family.
Plant Traits, Other Types
C. horizontalis plants are deciduous flowering shrubs. The plant form of Cotoneaster horizontalis is horizontally-spreading (thus the species name, horizontalis). The plants have small, roundish leaves that provide a nice contrast with larger-leafed plants. The fall foliage of its shiny leaves ranges from reddish-orange to burgundy. The light pink blooms of late spring yield later to equally shiny red berries (or "pomes"). The branching of rock cotoneaster is stiff and dense, giving the plant, overall, a rather bristly look. Stems shoot off the branches in what is often referred to as a "herringbone pattern." It is called this because it reminds one of the herringbone brick pattern sometimes found in patios and walkways. Actually, many would say it looks more like someone tried to form a row of V's along the branch, but failed. The left-hand strokes of the V's don't line up properly with the right-hand strokes, so that they never intersect. Rock cotoneaster reaches up to 3 feet in height and up to 8 feet in width.
The cotoneasters are a diverse group of plants and are roughly divided into ground-cover types (such as C. horizontalis) and taller, more upright types. Two types of C. horizontalis are the cultivar, 'Variegatus' (known for its two-toned leaves) and the variety, perpusillus (known for staying as short as 1 foot in height). But there are also many species beside horizontalis; for example:
- C. dammeri is one of the shortest types, reaching just 8 to 12 inches tall (zones 5 to 8).
- C. divaricatus is one of the kinds that grows tall enough (up to 6 feet in height, with a spread of up to 8 feet) to be used in a hedge (zones 4 to 7).
- C. lucidus is another kind commonly grown in hedges. It grows to be 6 to 10 feet high and wide (zones 3 to 7).
- C. salicifolius is one of the taller types at 10 to 15 feet tall, with a spread of slightly less than that (zones 6 to 8).
Sun and Soil Needs, Planting Zones
Grow rock cotoneaster in moist but well-drained, loamy soil. Although they are drought-tolerant shrubs once established, it's best not to abuse their "tolerance" when young. That is, young cotoneaster plants will profit from a touch of afternoon shade, even though they are considered ground covers for full sun. If you are growing young plants in full sun, be sure to give them plenty of water. Rock cotoneaster shrubs are cold-hardy to USDA plant hardiness zone 5. Not very good plants for hot climates, their southern limit is roughly zone 7. C. horizontalis is native to western China.
Rock Cotoneaster for Four-Season Interest
These shrubs offer a nice example of a plant with four-season interest. They produce their light pink flowers in late spring, and their unusual branching pattern hosts glossy green leaves in summer. But rock cotoneasters really come into their own in autumn. They bear both attractive fall foliage and berries in the autumn months. The red berries stay on the branches a long time and remain attractive into early winter. They may show signs of shriveling and discoloration by mid-winter. By late winter the berries may attract hungry wild birds.
Wildlife Attracted to the Plant, Uses in Landscaping
In fact, birds, bees, and butterflies are all attracted by these bushes. But, fortunately, they are deer-resistant shrubs. Birds use cotoneaster berries as an emergency food source in winter.
Because they stay low to the ground, rock cotoneaster plants are often used as ground covers and in rockeries (rock gardens). But others have trained them to grow up against walls. Grown at the top of a retaining wall on a hill, they will drape slightly over the side.
Care for Rock Cotoneaster
It is not necessary to prune cotoneaster plants unless you wish to contain their spread. And if you do prune them, don't prune off the ends of the branches, as you would, say, with yews. That would ruin their natural gracefulness.
That said, you might feel that a particular branch spoils the overall shape of the plant. In that case, follow the branch all the way back to the center of the shrub, and make your pruning cut there, so as not to leave an awkward stump behind.
Some growers do, indeed, want to restrict this plant's spread, and that is their reason for pruning it. Rock cotoneaster is one of those bushes that will strike down roots wherever one of its branches touches the ground. This enables it to spread quite a bit. Many people either are not interested in having the shrub spread that much or simply do not have the space to allow it to do so. If that describes your situation, then you will want to keep up with your pruning on this vigorous bush.
Name Origin, Mispronunciations
"Cotoneaster" is a widely mispronounced plant name. The correct pronunciation, technically, is cuh-TO-ne-AS-tuhr, but certain dictionaries give some legitimacy to the common mispronunciation, CAWT-tuhn-ES-tuhr. Others want to drop the first "e" altogether, fancying a combination of "cotton" and "aster."
In terms of the origin of the plant's name, "cotoneaster" comes from the new Latin word for "quince," cotneum, plus the suffix, -aster, meaning "imperfectly resembling." So a cotoneaster shrub is literally a plant that imperfectly resembles a quince (the reference is to Cydonia oblonga, not to flowering quince).