Cotoneaster horizontalis Decne. var. perpusillus
Rockspray cotoneaster
Rock cotoneaster is native to western China, but has escaped and is now found in some areas of North America.
Plants: prostrate, spreading horizontally over rock surfaces. They are 1–2½′ (30–76 cm) in height—the ones I have seen so far are plastered nearly flat against the rock. They may spread up to 8′ (2.4 m). Stems may have a distinctive fishbone pattern.
Leaves: Alternate, unlobed, dark green on top, light green and finely hairy below, ⅛–¼″ (6–8 mm) in length. Plants are semi-evergreen, retaining at least some leaves in winter; leaves become tinged with purple.
Flowers: Pale pink, ¼–⅜″ (8–10 mm) long, appearing from May to June.
Fruits: Berries are bright red, oval-shaped, ~3/16 ⨉ 1/16–⅛″ (5–6 ⨉ 3–4 mm), distributed evenly among the foliage. Each berry has three nutlets.
Habitats: Rocks, rocky slopes.
Online References:
Cotoneaster perpusillus
6/17/2012 · Coastal Maine Botanical Gardens, Boothbay, Maine · ≈ 14 × 9″ (35 × 23 cm) 
6/11/2025 · Coastal Maine Botanical Gardens, Boothbay, Maine · ≈ 10 × 6″ (24 × 16 cm) 
6/11/2025 · Coastal Maine Botanical Gardens, Boothbay, Maine · ≈ 6 × 4″ (16 × 11 cm) 
6/11/2025 · Coastal Maine Botanical Gardens, Boothbay, Maine · ≈ 10 × 6″ (24 × 16 cm) 
6/17/2012 · Coastal Maine Botanical Gardens, Boothbay, Maine · ≈ 7 × 4½″ (17 × 11 cm) 
| Kingdom | Plantae | Plants, but not fungi, lichens, or algae (from Stearn's Botanical Latin) |
| Subkingdom | Tracheobionta | Vascular plants—plants with a “circulatory system” for delivering water and nutrients |
| Division | Magnoliophyta | Flowering plants, also known as angiosperms |
| Class | Magnoliopsida | Dicotyledons—plants with two initial seed leaves |
| Subclass | Rosidae | Roses, legumes, proteas, dogwoods, hydrangeas, mistletoes, euphorbias, grapes, many more |
| Order | Rosales | Rose family and eight others |
| Family | Rosaceae | Includes apples, apricots, plums, cherries, peaches, pears, raspberries, strawberries, almonds, roses, meadowsweets, photinias, firethorns, rowans, and hawthorns; many others |
| Genus | Cotoneaster | From Latin for “quince-like,” possibly from the leaf shape |
| Species | horizontalis | Flat to the ground, horizontal |
| var. | perpusillus | From New Latin per- ”very small,“ or ”tiny“, and pusillus, ”very small,“ or ”little“ |
Cotoneaster horizontalis var. perpusillus description by Thomas H. Kent, not updated.
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