Rockspray cotoneaster is a low-growing, spreading shrub that is commonly used as a groundcover. It is native to China and has been introduced to other parts of the world, including the United States. The plant is named for its tendency to sprout new growth from the cracks and crevices in rocks. It has dark green leaves and white or pink flowers that bloom in the spring. The fruits are red and ripen in the fall.
About soil condition, the rockspray cotoneaster prefers well-drained soil but can tolerate some degree of drought once it is established. It also prefers full sun but can tolerate some shade, especially in hot summer climates.
Not too different with other cotoneasters, rockspray cotoneaster (Cotoneaster horizontalis) is an attractive, low-maintenance shrub. It's perfect for growing in rock gardens, as a groundcover or even as a cascading plant in containers. One of the best things about this cotoneaster is its tolerance of full sun to part shade. In fact, it needs at least four hours of sun each day to produce the best flowers and fruit.
The temperature conditions that are ideal for rockspray cotoneaster are temperatures that are cool, but not too cold. They should also be able to tolerate some amount of heat without being too stressed.
Ideal humidity condition for this plant is 50%. This plant cannot tolerate extremely dry or wet conditions. If the humidity is too low, the leaves will begin to turn brown and drop off. If the humidity is too high, the leaves will become yellow and fall off.
Regarding fertilizer, this kind of plant benefits from a combination of organic and inorganic matter. The organic part can be either compost or manure, while the inorganic part is typically a slow-release fertilizer. In terms of root system, the roots of rockspray cotoneaster are typically shallow, so it's important to make sure they're getting enough moisture.
Pruning rockspray cotoneaster (Cotoneaster horizontalis) is best done in late winter or early spring before new growth begins. You can prune to remove any dead or diseased wood, as well as to shape the plant. When pruning, make sure to cut just above a bud or leaf node.
Propagation of rockspray cotoneaster (Cotoneaster horizontalis) is best done by rooting hardwood cuttings taken from the plant in late fall or early winter. The cuttings should be 4 to 6 inches long and should include a heel, or a small piece of stem tissue attached to the bottom of the cutting. The cuttings should be placed in a planting mix that is 50 percent perlite or sand and 50 percent peat moss. The planting mix should be moistened and the cuttings should be placed in it so that the heel is just beneath the surface. The cuttings should be placed in a cold frame or covered with a plastic sheet to retain moisture.
Usually, the plant growth rate studies have been done on young plants in controlled settings. In these studies, rockspray cotoneaster typically grew between 6 and 12 inches per year. However, rockspray cotoneaster is known to be a fast-growing plant, so it is likely that growth rates are higher in the wild.
Common problems for this kind of plant are scale and aphids. Scale is a small, flat, sucking insect that infests the stems and leaves of the plant. Aphids are small, soft-bodied insects that feed on the sap of the plant. They can cause the leaves to turn yellow and the plant to become stunted.
Source:
Cotoneaster horizontalis - Rockspray Cotoneaster - plantfacts.osu.edu
Rockspray Cotoneaster - courses.missouristate.edu
Figure 12. Rockspray Cotoneaster (Cotoneaster microphylla - UC