Emerald Cushion Blue Moss Phlox

Overview

• Botanical name: Phlox subulata ‘Emerald Cushion Blue’. 

• Common name: Emerald Cushion Blue Moss Phlox / Creeping Phlox

• Habit: Forms a low, spreading mat (moss‑like), about 4–6 inches tall with a spread of about 12–24 inches (30–60 cm) under good conditions. 

• Bloom: In late spring its compact mat is blanketed with pale lavender‑blue flowers over dark green needle‑like foliage. 

• Hardiness: Rated in some sources to USDA Zones 2–9 for this cultivar. 

• Key features: Evergreen or semi‑evergreen foliage in some zones; excellent for rock gardens, slopes, front borders, edging; good drought tolerance once established. 

Light & Site Requirements

• Sunlight: Best in full sun (6+ hours of direct sunlight) to ensure strong bloom and dense habit. Some light part‑shade tolerated but performance may suffer. 

• Soil: Prefers very well‑drained soil. Performs especially well in sandy, gravelly or lean soils rather than heavy, wet clay. 

• Moisture: Medium to dry once established. Avoid sites that remain soggy or where water stands around the crown. 

• Placement: Ideal for front of border, rock garden, slope, ground cover under shrubs, or spilling over walls. Spreads outward to form the cushion effect. 

Planting & Maintenance

• Spacing & Planting: Space plants about 12–18″ (30–45 cm) apart so they can spread and fill in. At planting, ensure planting crown is level with soil. 

• Watering:

  • During establishment: Keep soil moderately moist.

  • Once established: Tolerates dry periods well; do not let soil remain soggy.

• Pruning / Shearing: After bloom, lightly shear or trim the foliage edge to promote denser mat and possibly a later secondary flush of lower bloom. 

• Division: Every few years (e.g., every 3‑4 years) you may divide or lift portions if the centre thins out; best in early fall or spring. 

• Winter care: Minimal; ensure the soil is not heavy or waterlogged in winter; good drainage helps avoid crown rot or freeze‑thaw damage.

Cold‑Climate / Zone 3 Considerations

• With hardiness to Zone 2–9 in some listings, this cultivar is quite suitable for northern climates such as yours. 

• Site selection is critical: full sun, excellent drainage, avoid low spots where snowmelt or standing water accumulates.

• Because it remains low, snow cover may help buffer it in winter, but excessive wet from melt is more of a threat than cold itself.

• In very exposed conditions, a thin light mulch may help crown protection, but avoid heavy mulch that traps moisture.

• If bloom is delayed in spring, the plant will catch up; the spring color is a major selling point in a Zone 3 landscape.

Photo from gardenia.net